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Your orientation to Raspberry Pi.

http://www.raspberrypi.org/

Status LED Indicator
OK  (Green) – SDCard Access       (D5 via GPIO16)
PWR (Red)   – 3.3 V Power         (D6           )
FDX (Green) – Full Duplex   (LAN) (D7 Model B   )
LNK (Green) – Link/Activity (LAN) (D8 Model B   )
10M (Yellow)- 10/100Mbit    (LAN) (D9 Model B   )

Click here for Raspberry Pi Schematic

STEP 01:

Download this quick start up guide to help you install your Linux OS on your Raspberry Pi.

STEP 02:

Get yourself a 4GB SD card, which is enough for use in many application.


NOTE: Not all SD cards work with the Raspberry Pi. High speed cards can be too fast for the Raspberry Pi bus. Check out which SD card is suitable for your Raspberry Pi. It has a lists of cards that have and have not worked for Raspberry Pi users. http://elinux.org/RPi_SD_cards

You may also like to check out the various peripherals that are compatiable to Raspberry Pi.
http://elinux.org/RPi_VerifiedPeripherals

STEP 03:

Format your SD card with SD Formatter 4.0 for SD/SDHC/SDXC
SDFormatter4exe.zip (5.99MB)

STEP 04:

You can download the image version New Out Of Box Software (NOOBS), extract all the files and copy into your SD card.

Insert this SD card into your Raspberry Pi, and power on it. Follow the instruction on your screen display to complete the installation process.

STEP 05:

You will be ask to select an Linux OS to install on your Raspberry Pi.

Choose the recommended “Raspian”, which is also the Raspbian “wheezy”.

The installation process will proceed.

Proceed to step 10.

Installing Raspbian operating system onto my Raspberry Pi.

STEP 06:

As of 02 Nov 2013, Raspbian now supports and pre-installed with Java.

Note: For those who want to run Java SDK on Raspberry Pi.

Raspbian “wheezy” is the recommended Linux OS for Raspberry Pi. This version is optimized to be run by Raspberry Pi which is using RP’s ARM processor supporting ‘hard-float’. However Java SDK only support ‘soft-float’ at this point in time (Jul 2013).

This call for another Debian Linux version which is known as Soft-float Debian “wheezy” (It is same as Raspbian “wheezy”, except that it will be slower. Use this version if you need to run Java JDK Linux ARM)

STEP 07:

Download and run the Win32DiskImager on your Windows Operating System.
win32diskimager-v0.8-binary.zip (5.67MB)

You can download the latest version at this website,
http://sourceforge.net/projects/win32diskimager/

STEP 08:

Unzip the Debian Linux version Soft-float Debian “wheezy”, which is a “2013-05-29-wheezy-armel.img” file.

Run the program Win32 Disk Imager.
a) Select the Image File “2013-05-29-wheezy-armel.img”
b) Select the Device, which is your storage drive for your SD card.
c) Click on the <Write> button to write the raw image onto your SD card.

Note: You can also use Win32 Disk Imager software to backup (clone)your existing SD card image, by click on the <Read> button, and choosing a *.img file name.

STEP 09:

Insert the SD card into your Raspberry Pi and power it up.

STEP 10:

On the first boot, the “raspi-config” menu will pop up.

Note: If you are at the command shell prompt. You can key in “sudo raspi-config” to access to this menu.

“raspi-config” menu

Note: You may find yourself having problem when trying to key in the ‘#’ char by pressing <Shift+’3′>. A ” pound char may be generated instead.

This is because the Raspberry Pi’s default locale code is set as UK. You will need to set the locale code to US, for a US keyboard layout.

Key in the following command,
“sudo dpkg-reconfigure keyboard-configuration”

Alternative method to configure you keyboard layout.
a) key in “sudo nano /etc/default/keyboard”
b) look for the line containing “XKBLAYOUT=”gb””.
c) change “gb” to “us” for US keyboard layout.
d) save and exit.
e) reboot or key in the following “invoke-rc.d keyboard-setup start”, to reload the keymap.

STEP 11:

Select <1> and press enter to Expand Filesystem.

If you are connected to the network, select <8 Advanced Options> and press enter.

<A2 Hostname> to change the hostname default “raspberrypi”.

“raspi-config” menu 8-A

To change to the Standard US Keyboard mapping, select <4 Internationalisation Options>,

<I1 Change Locale>, with the following options,
Default Locale : None

<I2 Time Zone >, with the following options,
Geographic area: Asia
Time Zone      : Singapore

<I3>, with the following options,
Keyboard model : “Generic 105-key (Intl) PC”
Keyboard layout: “Others” -> “English (US)”
AltGr as       : “The default for the keyboard layout”
Compose Key    : “No compose key”
Ctrl+Alt+Backsp: “No”, (don’t use it to terminate Xserver)

You can also configure to allow the system to boot directly straight into the GUI desktop, using this raspi-config.

Select <Finish> then press enter to proceed to the system command shell.

You can always come back to this raspi-config menu again by executing the command “sudo raspi-config” from the shell command.

“raspi-config” menu 4-I

Raspberry Pi revision 2, header pins out.

This is my Raspberry Pi. I have custom built a prototyping board that can be plugged on top of my Raspberry Pi. This prototyping board is soldered with 2.54mm housing connector (2 rows of 13 pins) so that I can easily access to the I/O pins of my Raspberry Pi.

My LED indicator wiring is as follows,
LED0 – GPIO_17 (Pin11)
LED1 – GPIO_18 (Pin12)
LED2 – GPIO_27 (Pin13)
LED3 – GPIO_22 (Pin15)
LED4 – GPIO_23 (Pin16)
LED5 – GPIO_24 (Pin18)
LED6 – GPIO_29 (Pin22)

UART (serial communication) wiring,
Gnd –         (Pin06)
TXD – GPIO_14 (Pin08)
RXD – GPIO_15 (Pin10)

SPI (serial communication) wiring,
MOSI – GPIO_10 (Pin19)
MISO – GPIO_09 (Pin21)
SCLK – GPIO_11 (Pin23)
CE0  – GPIO_08 (Pin24)
CE1  – GPIO_07 (Pin26)

I2C (serial communication) wiring,
SDA0 – GPIO_02 (Pin03)
SCL0 – GPIO_03 (Pin05)

Information taken from
http://www.mosaic-industries.com/embedded-systems/

Learning to control Raspberry Pi general purpose I/O pin 11 (which is known as GPIO_0, or GPIO_17 if base on BCM2835 IC pin assignment)Power on my Raspberry, and the operating system will prompt for my raspberrypi login.Key in “pi” for the login, and “raspberry” for the password.

raspberrypi login: pi
Password: raspberry

pi@raspberrypi ~ $

Setup or initialise I/O port 17, by sending text “17” to the operating file system “/sys/class/gpio/export”

A directory folder will be created. “/sys/class/gpio/gpio17/”

Reference:
http://elinux.org/RPi_Low-level_peripherals#GPIO_Driving_Example_.28C.29

I am able to control the I/O pins on my Raspberry Pi, but I want to larn more into controlling the I/O pins using native C. Controlling I/O pins using the “file directory system” like method will be very slow.The speed achieved base on this benchmark website, I/O control through this shell (or file directory system) method, achieved a maximum process speed of about 6.8kHz (2x 3.4kHz).To achieve a higher speed, I will need to use native C programming, which can process from 9.4Mhz to 44Mhz (2x 4.7Mhz to 22Mhz).

More things to learn…

References:

Notes regarding digital I/O pins, https://www.kernel.org/doc/Documentation/gpio.txt

UART

The UART port is actually pin8 (TxD) and pin10 (RxD) on the Raspberry Pi connectors. The UART signal is 3.3V.You can use RS232/RS422/RS485 communication to talk to the UART, but a level shifter (for example MAX3232) required. RS232 uses about +/- 7 to 13V, while UART uses digital voltage (1.8V, 3.3V or 5V). For our Raspberry Pi UART, it is 3.3V. More information about making your own level shifter, you can visit this page. There are also standard USB to UART products for interfacing to your Raspberry Pi.The Raspberry Pi default operating system uses this UART port as its diagnostic port. This port has the following default UART settings,
– Baudrate   : 115200bps
– Data       : 8 bits
– Parity     : None
– Handshaking: NoneThis default port act as another Linux shell terminal screen, as you would have seen on the screen through the Raspberry Pi’s HDMI or video output.

You can use a terminal program to access through this port.Using the Window’s Hyperterminal program, setup the correct com port settings. And connect the terminal. You will see nothing on the terminal screen, but actually the Raspberry Pi is prompting you for your login ID. This ID is “pi” which is similar to how you log on to your typical terminal screen. You will see the terminal replying you with the prompt for password. Key in the default password “raspberry”. You shall get a similar print out from the terminal program, as on the right. ->Looks very much like the typical terminal on your local display. This is mainly for troubleshooting, diagnostic or perhaps used for remote access of your Raspberry Pi.

raspberrypi login: pi
Password:
Last login: Wed Jun 19 15:36:44 UTC 2013 on tty1
Linux raspberrypi 3.6.11+ #474 PREEMPT Thu Jun 13 17:14:42 BST 2013 armv6lThe programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
pi@raspberrypi:~$

The UART on the Raspberry Pi is quite an useful peripheral. For me, I would like to use this UART as a serial communication to control my other circuit modular.

In order to use this UART, I need to disable the diagnostic features from the operating system’s boot up. This means that I do not want the system to setup the UART pins as diagnotic port, when the system boots up.

The following command is key in to edit the system boot up script. vi is an text editor program, which is not very user friendly.Alternative, you can use nano editor instead of vi for the text file editing.
Or gedit editor. You can install then if they are not installed.
“sudo apt-get install nano” or
“sudo apt-get install gedit ” To learn how to use the vi editor, click on the following link, http://www.unix-manuals.com/tutorials/vi/vi-in-10-1.html

A summary of the vi editor’s command is summeries as follows, http://osr600doc.sco.com/en/FD_create/vi_summary.html

After the vi command, you should see the following screen display. This is the vi editor diaplaying the text in the “cmdline.txt file”.The objective is to delete the text (in red color), which is relating to the UART setup. Press ‘l’ on your keyboard to shift the cursor to the right, until it is at the position of the char that we want to delete. Move the cursor under the first char ‘c’ (char as illustrated in red).Press ‘x’ on your keyboard to delete the char one by one. You should observed the delete action.When all the text in red are deleted, press ‘:w’ on your keyboard, follow by a enter key to save the text file.Press ‘:q’ on your keyboard, follow by a enter key to exit the vi program.If at anytime you have edit wrongly, you can enter the command ‘:q!’ on your keyboard, to exit the vi program without saving the text file.

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
~
~
~
~
~
~

Find and comment away the line containing the following text (near the end of the file),
“T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100”,
by pressing the ‘j’ on your keyboard to scroll down line by line.Issue an insert command by pressing ‘i’ to insert some text before the cursor. Insert a char ‘#’ at the beginning of the line to comment the whole line. The ‘#’ mask off the whole line. The line that are masked off will not be intepreted by the system.After the ‘#’ char is inserted, press <Esc> key on your keyboard to end the insert command that was issued.Press ‘:w’ save the text file.

Press ‘:q’ to exit the vi program.

The UART device name is /dev/ttyAMA0
Now the UART is not in use by the Linux Raspbian operating system, and is available for my own use.

To test the UART serial communication port, we can install a program call minicom. The use of minicom is similar to hyperterminal program that I use in Windows operating system (OS).

Enter the command “sudo apt-get install minicom“

There are also alternative GUI based serial communication program, cutecom.

To run the minicom terminal program. Key in the following command “sudo minicom -b 9600 -o -D /dev/ttyAMA0“.

-o              (skip initialisation)
-D /dev/ttyAMA0 (specify the serial port)

Key in command “man minicom” to find out the other options that you can set with the minicom program.

Configuration Settings:
Baudrate : 9600bps
Data bit : 8    (default)
Stop bits: 1    (default)
Parity   : None (default)

Apply the configuration settings to serial port “ttyAMA0”. The label tty (known as teletype) denotes all serial communication that the linux operating system is handling. In Raspberry Pi, ttyAMA0 refers to the pin8 (TxD) and pin10 (RxD).

When you type a char on your keyboard, an ascii char code is actually sent out of the Raspberry Pi ‘s pin8 (TxD). You will not be able to see it on the screen. What you will see on your screen will be those serial data that the Raspberry Pi received through pin10, which is the RxD.

In order to see what we have transmitted out from TxD, we can short the pin8 (TxD) and pin10 (RxD) together. This means that what you send will be receive and display on the display. The serial port configuration for the TxD and RxD is the same, so the serial data that is received will be exactly what you have transmitted.

The following text “Hello World!!! ” were typed on the keyboard after shorting the RxD and Txd pin. The text will be displayed, indicating that the UART is working properly.

Now that you know that the UART on your Raspberry Pi is ready for use, you can use it to communicate with many other peripheral.

Press <Ctrl + ‘A’>, followed by <‘X’>, then key in enter for “Yes” to quit the minicom program.

pi@raspberrypi ~ $ sudo minicom -b 9600 -o -D /dev/ttyAMA0

——————————————-
Welcome to minicom 2.6.1OPTIONS: I18n
Compiled on Apr 28 2012, 19:24:31.
Port /dev/ttyAMA0Press CTRL-A Z for help on special keysHello World!!!

CTRL-A Z for help | 9600 8N1 | NOR | Minicom 2.6.1 | VT102 | Offline
——————————————-

Setting up the serial port with other settings,
Baudrate : 115200bps
Data bit : 8    
Stop bits: 1    
Parity   : Even

SPI

The SPI port onboard the Raspberry is disable by default. The first thing to do is to enable the SPI port.

Edit the file “/etc/modprobe.d/raspi-blacklist.conf”

Comment off the line “blacklist spi-bcm2708” with a # in front.

Key in Ctrl+’X’ to exit, then ‘Y’ yes to save the change to the file, and finally ‘Enter’. This will brings you back to the command prompt.

pi@raspberrypi ~ $ sudo nano /etc/modprobe.d/raspi-blacklist.conf

GNU nano 2.2.6 File: /etc/modprobe.d/raspi-blacklist.conf Modified

# blacklist spi and i2c by default (many users don’t need them)

#blacklist spi-bcm2708
blacklist i2c-bcm27088

Check to see if the SPI is successfully enable in the Raspberry Pi.

You should see “/dev/spidev0.0 /dev/spidev0.1” created.

0.0 means SPI0 CS0 (CS is the chip select)
0.1 means SPI0 CS1

pi@raspberrypi ~ $ ls /dev/spidev*
/dev/spidev0.0 /dev/spidev0.1
pi@raspberrypi ~ $

Testing the SPI port

download this SPI loopback test code written in ‘C’ programming language.

spidev_test.c

Compile the *.c file using gcc command,then run the compiled program.

You should see the following hex dump data, indicating all 0x00.

This means that the SPI is receiving nothing, no data.

pi@raspberrypi ~ $ gcc spidev_test.c -o spidev_test
pi@raspberrypi ~ $ sudo ./spidev_test -D /dev/spidev0.0
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00
pi@raspberrypi ~ $

Now we do a SPI data loopback test.
Short the pins MISO (GPIO 9, Pin21) and MOSI (GPIO 10, Pin19) on your Raspberry Pie. This will enables the SPI MISO to received whatever data that is sent out from the MOSI pins.

From this test, we will be able to know if SPI hardware for sending and receving is working ok. Whatever that is sent out, the data should be properly received.

Run the compiled program again.

You should see the following hex dump data. This means that your SPI peripheral is working fine.

spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

FF FF FF FF FF FF
40 00 00 00 00 95
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
DE AD BE EF BA AD
F0 0D
pi@raspberrypi ~ $

I2C

The SPI port onboard the Raspberry is disable by default. The first thing to do is to enable the SPI port.

Edit the file “/etc/modprobe.d/raspi-blacklist.conf”

Comment off the line “blacklist i2c-bcm2708” with a # in front.

Key in Ctrl+’X’ to exit, then ‘Y’ yes to save the change to the file, and finally ‘Enter’. This will brings you back to the command prompt.

pi@raspberrypi ~ $ sudo nano /etc/modprobe.d/raspi-blacklist.conf

GNU nano 2.2.6 File: /etc/modprobe.d/raspi-blacklist.conf Modified

# blacklist spi and i2c by default (many users don’t need them)

blacklist spi-bcm2708
#blacklist i2c-bcm27088

Edit the file “/etc/modules”

Add in “i2c-dev” to the end of the file.

Key in Ctrl+’X’ to exit, then ‘Y’ yes to save the change to the file, and finally ‘Enter’. This will brings you back to the command prompt.

pi@raspberrypi ~ $ sudo nano /etc/modules

# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with “#” are ignored.
# Parameters can be specified after the module name.

snd-bcm2835
i2c-dev

Allow Pi User to Access I2C peripheral.

This allow configuration of the software.

Check to see if the SPI is successfully enable in the Raspberry Pi.

You should see “/dev/i2c-0 /dev/i2c-1” created.

pi@raspberrypi ~ $ ls /dev/i2c*
/dev/i2c-0 /dev/i2c-1
pi@raspberrypi ~ $

Running the test program.

You will see that there is a total of 0x77 or 119 blanks “–“. This indicates that no I2C devices is detected on the bus.

Other command:
– ifconfig eth0 (display the first ethernet adaptor)
– ifconfig -a (show all network interface, active or inactive)
– traceroute

Install Samba on the system so that my Raspberry Pi can be access from a Window operating system.

Ensure that the network cable (internet enabled) is plugged onto the Raspberry Pi before powering on the board. Enter the following command to install samba software. The process will fetch the installation from the internet.

Search for the section marked ##### Authentication #####,
Change the following text “# security = user” to “security = user”.
To save the text file, Press “Ctrl+X”, then ‘Y’, then enter.

Use command “hostname -I” to check the IP address.

Alternate command “ifconfig” to check the IP address of my Raspberry Pi, which IP address is “192.168.1.99”

pi@raspberrypi ~ $ hostname -I
192.168.1.99

pi@raspberrypi ~ $  ifconfig
eth0  Link encap:Ethernet  HWaddr b8:27:eb:dc:ee:af
      inet addr:192.168.1.99  Bcast:192.168.1.255  Mask:255.255.255.0
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:337 errors:0 dropped:0 overruns:0 frame:0
      TX packets:198 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000
      RX bytes:30734 (30.0 Kib)  TX bytes:20136 (19.6 Kib)

Go to window’s to map a network drive. The network folder path is “//192.168.1.99”. Check box for “Reconnect at logon” & “Connect using different credentials”

Check the network and port bind on the Raspberry Pi.

From the list, it can be seen that UDP port 6324 is currently being used by process ID PID 2361/java program.

Sometimes you may like to access to your Raspberry Pi without connecting your display monitor and your keyboard. This section provide a guide to allow access to your Raspberry Pi remotely through network connection.

How to locate your Raspberry Pi IP address from a remote computer?

The method above requires you to plugged a monitor display to your Raspberry Pi in order to obtain its IP address. The following method allows you to obtain raspberry pi address through thr

You can also check the IP address of your Raspberry Pi that is plugged into a dynamic network through the router webserver. Typical router’s IP address for a local network is 192.168.1.1. You will need your user name and password to log into the router’s webserver. From the webserver, you should be able to locate the device name “raspberrypi” (or known as hostname) and its allocated dynamic IP address and its MAC address.

Alternative, you can use this software “Advance Port Scanner” to scan for your Raspberry Device on the network.

pi@raspberrypi ~ $ hostname
raspberrypi

Note: To change the Raspberry Pi’s hostname “raspberrypi”, use nano text editor to edit the following file “/etc/hostname” and “/etc/hosts”. Replace the old hostname “raspberrypi” to your new hostname. Your new hostname can only contains lower/upper case character, numbers, and ‘-‘.

Your new hostname will appear on the raspberry prompt, after the device reboot.

pi@raspberrypi ~ $ sudo nano /etc/hostname

pi@raspberrypi ~ $ sudo nano /etc/hosts

pi@raspberrypi ~ $ sudo reboot

pi@newHostname ~ $

Download this program MobaXterm, and install in your Window operating system. You can download from http://mobaxterm.mobatek.net/


Alternative, you can also use this program call Putty.
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

Alternative, you can also use this program call Filezilla
https://filezilla-project.org/ (for Microsoft Windows OS).
or (for Linux OS) “sudo apt-get install filezilla”

These program allow SSH connection logging in to your Raspberry Pi. You will be able to see what you would see with the display monitor and keyboard connected to your Raspberry Pi

Run the installed MobaXterm program.
Click on “Session”->”Open New Session”.
Choose “SSH” as the session type.
Key in the IP address of your Raspberry Pi.
The standard port number for SSH Remote Login Protocol is 22.

Click “OK” to connect to your Raspberry Pi.

Key in the Login user name “pi”, then press enter, and
standard password “raspberry” then press enter key.

You will see the following display as on the right.

Login: pi
Permanently added ‘192.168.1.95’ (ECDSA) to the list of known hosts.
rasppi@192.168.1.95’s password:
Linux raspberrypi 3.6.11+ #474 PREEMPT Thu Jun 13 17:14:42 BST 2013 armv6lThe programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Mon Jul 22 13:47:57 2013
pi@raspberrypi ~ $

You may encounter the following error on the right.
If not, you can skip this section.
This happens when you login successfully for the first time, but then you reinstall the server. The key becomes different, and you get prompt for this security message.Access into your Raspberry Pi and key in the following command,
“rm -f ~/.ssh/known_hosts“
Delete from your client computer.
C:\Users\LSB\Documents\MobaXterm\home\.ssh\known_hosts.

You may need to reboot the Linux in order for the change to take effect “sudo reboot”.

It should solve the problem. For more information regarding this issue, you can visit the following website,
http://www.geekride.com/ssh-warning-remote-host-identification-has-changed/

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that a host key has just been changed. The fingerprint for the RSA key sent by the remote host is xx:xx:xx:xx:b1:66:fd:05:0c:43: …. … .. .

pi@raspberrypi ~ $ leadpad&

pi@raspberrypi ~ $ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO…
…
…
Thread model: posix
gcc version 4.6.3 (Debian 4.6.3-14+rpi1)

Key in the following hello world source code into the nano editor.

When finish typing in the source code text, press CTRL+X to save this file “main.c”, press ‘Y’ to confirm. Press enter key to finish the process.

#include <stdio.h>

int main()
{
   printf(“Hello World!!!”);
   return(0);
}

For compiling C++ language (*.cpp file), use g++ compiler.

pi@raspberrypi ~ $ python -V
Python 2.7.3

Key in the following hello world source code into the nano editor.

When finish typing in the source code text, press CTRL+X to save this file “hello.py“, press ‘Y’ to confirm. Press enter key to finish the process.

#!/usr/bin/python

print “Hello World!!!”nt “Boon, you’re awesome”
else :
print “Hello”, name

Using Python to control the digital I/O port.
Before starting to program your I/O on Raspberry Pi, we will need to download and setup the library.

pi@raspberrypi ~ $ wget http://pypi.python.org/packages/source/R/RPi.GPIO/RPi.GPIO-0.1.0.tar.gz
pi@raspberrypi ~ $ tar zxf RPi.GPIO-0.1.0.tar.gz
pi@raspberrypi ~ $ cd RPi.GPIO-0.1.0
pi@raspberrypi ~ $ sudo python setup.py install

Try controlling the Raspberry Pi’s digital I/O GPIO1 (pin12 of the header, GPIO18) as output port, using Python script.

1) import RPi.GPIO
2) setup I/O direction, as output port.
3) set digital I/O port to logic ‘1’, high
4) set digital I/O port to logic ‘0’, low

You should see the LED lights up and switched off, if wired an indicator to pin 12.

pi@raspberrypi ~ $ sudo Python
>>> import RPi.GPIO as GPIO
>>> GPIO.setup(18, GPIO.OUT)
>>> GPIO.output(18, True)
>>> GPIO.output(18, False)

#!/usr/bin/python

import sys
import time
import serial

#print title
print(“start python program.”)#print out the arg passed from command line
for arg in sys.argv:
  print arg#delay 0.1sec
time.sleep(0.1)
#delay 1.0sec
time.sleep(1) #setup serial port
port = serial.Serial(“/dev/ttyAMA0”, baudrate=115200, timeout=3.0)#get user input
name = raw_input(‘what is your name? ‘)#conditional statement
if name == ‘Boon’ :
  print “Boon, you’re awesome”
else :
  print “Hello”, name

#while loop
while True:
  port.write(“\r\nSay something:”)
  rcv = port.read(10)
  port.write(“\r\nYou sent:” + repr(rcv))

#!/usr/bin/python

import time
import RPi.GPIO as GPIO

GPIO.setup(11, GPIO.IN)
while True:
  mybutton = GPIO.input(11)
  if mybutton == False:
    print “giggle”
  time.sleep(.2)

Note: As of Nov 2013, the official operating system for Raspberry Pi “Raspian” is installed with Java by default. Proceed to the step for installing Pi4J.

Installing Java to your Raspberry Pi

First, we will need to download and instal the Java JDK onto the Raspberry Pi.Do take note that the JDK version that we will be downloading is meant for Linux ARM processor “Linux ARM v6/v7 Soft Float ABI”.
(28 July 2013)
JDK for Linux ARM, “jdk-21-linux-arm-sfp.tar.gz (65.12MB)”

You can download the lastest version of this file from this Java website,
http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

Remember to accept the Oracle Binary Code License Agreement for Java SE.

Check that the Java environment variable is setup correctly.

Note: If the following error is encountered when the command “java -version” is executed.
java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory

It is propably that you have installed the incorrect version of Debian Linux. At this point in time, Java SDK for Linux ARM has yet to support.

Please refer to the previous section, for the installtion of the correct Debian Linux version for use with Java SDK Linux ARM.

Check if PI4J is installed correctly.
Go to PI4J directory.
Compile the example “WiringPiGpioExample.java”.
Run the compile java program “WiringPiGpioExample”.

I am able to see my rows of LED lighting up in a wave sequence, up and down non-stop.

pi@raspberrypi ~ $ cd /opt/pi4j/examples/
pi@raspberrypi /opt/pi4j/examples $ sudo javac -classpath .:classes:/opt/pi4j/lib/’*’ -d . WiringPiGpioExample.java
pi@raspberrypi /opt/pi4j/examples $ sudo java -classpath .:classes:/opt/pi4j/lib/’*’ WiringPiGpioExample

Testing out with a simple Java program.
Let us do a hello world example.

Key in “nano hello.java”.
This will open a text editor for us to key in the java source code for our hello world example.

Key in the following java source code.

Press ‘Ctrl+X’ to exit, then ‘Y’ to save, then press ‘Enter’.

pi@raspberrypi ~ $ nano hello.java

class hello
{
   public static void main(String args[])
   {
      System.out.println(“Hello World!”);
   }
}

Compile the java source code “hello.java”, a java compiled file “hello.class” will be generated.

pi@raspberrypi ~ $ javac hello.java

To run the program, key in “java hello”.

You should be able to see the printed text “Hello World!” after execution.

pi@raspberrypi ~ $ java hello
Hello World!

Looking back to the wiringPi, which is the library for java to access to the native hardware I/O on the Raspberry Pi.

Taking a look at the java code using pi4j wiringPi.

– WiringPiGpioExample.java

Run the java program.

You may notice “wiringPiSetup: Unable to open /dev/mem”. This means that you do not have access to the hardware.

Run the java program with the “sudo” in front as follows.

You should see the LED light running from left to right.

pi@raspberrypi ~ $ java -classpath .:classes:/opt/pi4j/lib/’*’ WiringPiGpioExample

<–Pi4J–> GPIO test program
wiringPiSetup: Unable to open /dev/mem: Permission denied
==>> GPIO SETUP FAILED

pi@raspberrypi ~ $ sudo java -classpath .:classes:/opt/pi4j/lib/’*’ WiringPiGpioExample

<–Pi4J–> GPIO test program

Serial Java Programming with pi4j on Raspberry Pi

– SerialExample.java

Run the “SerialExample.java“

If you encounter error when opening the serial port, do check out the eariler posting to ensure that the serial port is properly configured.

CURRENT TIME: Mon Nov 04 12:23:23 SGT 2013
Second Line
Third Line
CURRENT TIME: Mon Nov 04 12:23:24 SGT 2013
Second Line
Third Line
CURRENT TIME: Mon Nov 04 12:23:25 SGT 2013
Second Line
Third Line

Java examples (taken from www.pi4j.com)

– WiringPiGpioExample.java
– ControlGpioExample.java
– ListenGpioExample.java
– ShutdownGpioExample.java
– TriggerGpioExample.java
– SerialExample.java
– SystemInfoExample.java

Linux bash script for launching/starting Java program. The command to launch Java is similar to those in WinOs, except for some notation changes. Note the use of char ‘:’ as the seperator and the slash ‘/’ for its file path. WinOS uses ‘;’ and the backslash ‘\’.
The script is similar to the batch file used in WinOS.

The following is an example of the script,
“run.sh“

Key in “. run.sh” to run the script in Linux command prompt.
Note: remember to make this file “run.sh” executable. (see examples in this website.)

inside file “run.sh”
#!/bin/bash
echo “Running SmartHomeSensors Java Program…”
java -classpath .:bin:lib/log4j-1.2.14.jar:lib/commons-logging-1.1.jar:classes:/opt/pi4j/lib/’*’:lib/json-simple-1.1.1.jar:lib/org.apache.httpcomponents.httpclient_4.3.1.jar:lib/utilities.jar:resource com.picControl.smartHomeSensors.MyMain

pi@raspberrypi ~ $ . run.sh

To auto run the script which launch the java program upon Raspberry Pi boot up (startup), edit the file “rc.local”.

Add in the following to the file,

cd /home/pi/smartHomeSensor
echo “Run script for SmartHomeSensor Java program”
SCRIPT=”/home/pi/smartHomeSensor/run.sh”
echo “run script \”-> $SCRIPT\””
sudo $SCRIPT &

The add command set the current directory to the project folder. During the boot process, it cannot be assume that you are in the user directory. Reference to the root directory to be safe.

Use sudo to run the script, and make the script run in the background.

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will “exit 0” on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ “$_IP” ]; then
   printf “My IP address is %s\n” “$_IP”
fi

cd /home/pi/smartHomeSensor
echo “Run script for SmartHomeSensor Java program”ensor Java program”
SCRIPT=”/home/pi/smartHomeSensor/run.sh”
echo “run script \”-> $SCRIPT\””
sudo $SCRIPT &

exit 0

pi@raspberrypi ~ $ sudo nano /etc/rc.local

Login to check if the java process is running.
command “ps ax” print out the list of processes (thread) currently running in Raspberry Pi. “| grep java” pipe the output result and print out only those result that have the word “java” in it.

The result shows that the java program is running with PID 2242 (process ID). Remember this number, for you may need to use it to kill the process.

pi@raspberrypi ~ $ ps ax | grep java
2242 ? Sl 0:44 java -classpath .:bin:lib/log4j-1.2.14.jar:lib/commons-logging-1.1.jar:classes:/opt/pi4j/lib/*:lib/json-simple-1.1.1.jar:lib/org.apache.httpcomponents.httpclient_4.3.1.jar:lib/utilities.jar:resource com.picControl.smartHomeSensors.MyMain
2461 pts/0 S+ 0:00 grep –color=auto java

Now grep “run.sh”. Notice the PID 2241.

This is generated before the Java program is launch. Remember this PID no. You may need this number to kill the same java program.

pi@raspberrypi ~ $ ps ax | grep run.sh

2233 ? S 0:00 sudo /home/pi/smartHomeSensor/run.sh
2241 ? S 0:00 /bin/bash /home/pi/smartHomeSensor/run.sh
2481 pts/0 S+ 0:00 grep –color=auto run.sh

pi@raspberrypi ~ $ sudo kill -9 2242
pi@raspberrypi ~ $ ps ax | grep run.sh
2487 pts/0 S+ 0:00 grep –color=auto run.sh
pi@raspberrypi ~ $ ps ax | grep java
2489 pts/0 S+ 0:00 grep –color=auto java

Commands Illustration

Access to /sys directory which is hidden.
Containing system peripherals directory/information, for example GPIO, I2C, tty (UART, teletype).
http://www.linusakesson.net/programming/tty/index.php

To get help or further details for any linux command, use the “man” command.
Help manual for any command or program, where ???? is the command/program name.

Display the content of the file “XXXX”.
Example to display Raspberry Pi hardware revision, key in “cat /proc/cpuinfo“

Example to display Linux OS information, key in “cat /etc/lsb-release”

Hardware : BCM2708
Revision : 000e
Serial : 000000005fdceeaf

Command “PS” List the program or threads running in the background of the Linux operating system (for the current user session only).
Where PID is the process ID number.

Command “ps” is a useful troubleshooting tools. Other related command is “top”.

Other useful troubleshooting commands are,
– “strace“, “ltrace“
– “mtrace“

pi@raspberrypi ~ $ ps
PID TTY TIME CMD
2803 pts/1 00:00:02 bash
2948 pts/1 00:00:00 ps

To list all the process running in the Raspberry Pi device, use command “PS AX”.
You can see the process created by other user session and you can kill it as well.

These are the bash session started by various user session 0, 1, 2, etc… ,

3477 pts/0 T 0:00 -bash
347? pts/1 T 0:00 -bash
347? pts/2 T 0:00 -bash

This is a bash session started for the main hardware,

2121 tty1 S+ 0:01 -bash

To list only the PID for a particular program, you can use with grep.

pi@raspberrypi ~ $ ps ax
PID TTY STAT TIME COMMAND
1 ? Ss 0:01 init [2]
2 ? S 0:00 [kthreadd]
3 ? S 0:00 [ksoftirqd/0]
5 ? S< 0:00 [kworker/0:0H]
6 ? S 0:01 [kworker/u:0]
7 ? S< 0:00 [kworker/u:0H]
8 ? S< 0:00 [khelper]
9 ? S 0:00 [kdevtmpfs]
10 ? S< 0:00 [netns]
12 ? S 0:00 [bdi-default]
13 ? S< 0:00 [kblockd]
14 ? S 0:00 [khubd]
15 ? S< 0:00 [rpciod]
16 ? S 0:00 [khungtaskd]
17 ? S 0:00 [kswapd0]
18 ? S 0:00 [fsnotify_mark]
19 ? S< 0:00 [nfsiod]
20 ? S< 0:00 [crypto]
27 ? S< 0:00 [kthrotld]
28 ? S< 0:00 [VCHIQ-0]
29 ? S< 0:00 [VCHIQr-0]
30 ? S< 0:00 [VCHIQs-0]
31 ? S< 0:00 [iscsi_eh]
32 ? S< 0:00 [dwc_otg]
33 ? S< 0:00 [DWC Notificatio]
35 ? S< 0:00 [deferwq]
36 ? S 0:00 [kworker/u:2]
37 ? S 0:08 [mmcqd/0]
38 ? S 0:00 [jbd2/mmcblk0p6-]
39 ? S< 0:00 [ext4-dio-unwrit]
154 ? Ss 0:00 udevd –daemon
1503 ? S 0:01 /usr/sbin/ifplugd -i lo -q -f -u0 -d10 -w -I
1592 ? S 0:07 /usr/sbin/ifplugd -i eth0 -q -f -u0 -d10 -w -I
1778 ? Sl 0:00 /usr/sbin/rsyslogd -c5
1863 ? Ss 0:00 /usr/sbin/cron
1888 ? Ss 0:00 dhclient -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhcli
1918 ? Ss 0:00 /usr/bin/dbus-daemon –system
1964 ? Ss 0:02 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 102:104
2003 ? Ss 0:00 /usr/sbin/thd –daemon –triggers /etc/triggerhappy/triggers.d
2008 ? Ss 0:00 /usr/sbin/sshd
2037 tty1 Ss 0:00 /bin/login -f tty1
2038 tty2 Ss+ 0:00 /sbin/getty 38400 tty2
2039 tty3 Ss+ 0:00 /sbin/getty 38400 tty3
2040 tty4 Ss+ 0:00 /sbin/getty 38400 tty4
2041 tty5 Ss+ 0:00 /sbin/getty 38400 tty5
2042 tty6 Ss+ 0:00 /sbin/getty 38400 tty6
2044 ? Sl 0:01 /usr/sbin/console-kit-daemon –no-daemon
2111 ? Sl 0:00 /usr/lib/policykit-1/polkitd –no-debug
2121 tty1 S+ 0:01 -bash
2151 ? S 0:00 [kworker/0:0]
2249 ? Ss 0:00 sshd: pi [priv]
2256 ? S 0:00 sshd: pi@notty
2257 ? Ss 0:00 /usr/lib/openssh/sftp-server
2258 ? Ss 0:00 /usr/lib/openssh/sftp-server
2662 ? S 0:00 [flush-179:0]
2663 ? Ss 0:00 sshd: pi [priv]
2667 ? Ss 0:00 sshd: pi [priv]
2674 ? S 0:01 sshd: pi@pts/0
2678 ? S 0:00 sshd: pi@notty
2679 ? Ss 0:00 /usr/lib/openssh/sftp-server
2684 pts/0 Ss 0:03 -bash
3127 ? S 0:00 udevd –daemon
3130 ? S 0:00 udevd –daemon
3338 ? S 0:00 [kworker/0:1]
3393 ? Ss 0:00 sshd: pi [priv]
3397 ? Ss 0:00 sshd: pi [priv]
3404 ? S 0:00 sshd: pi@pts/1
3408 ? S 0:00 sshd: pi@notty
3409 ? Ss 0:00 /usr/lib/openssh/sftp-server
3416 pts/1 Ss+ 0:01 -bash
3469 ? S 0:00 [kworker/0:2]
3476 pts/0 R+ 0:00 ps ax
3477 pts/0 T 0:00 -bash
3478 pts/0 Tl 0:03 java -classpath .:bin:lib/log4j-1.2.14.jar:lib/commons-logging

pi@raspberrypi ~ $ ps ax | grep java
3478 pts/0 Tl 0:03 java -classpath .:bin:lib/log4j-1.2.14.jar:lib/commons-logging

To terminate the program running in the background thread, use the kill command. Where “####” is the process ID (PID)

Putting an option -9 will force the process to be killed.

The process PID can be kill from another user session, even if the PID is not listed in its session.

pi@raspberrypi ~ $ kill ####

or

pi@raspberrypi ~ $ kill -9 ####

To run the “bash_script.sh” without the command bash, set the file as executable and run the file.

Note: You may encounter with the following
./test.sh: /bin/bash^M: bad interpreter: No such file or directory.

There is a ‘^M’ char detected at the end of the first line. Ensure that the script is not written on a Microsoft Window OS. Window’s environment will append ‘^M’ for enter key.

Use vi editor to view the file.
Type in command “vi bash_script.sh”.
You will see the ‘^M’ char in blue.
Delete those char.

Press ‘:w’ save the text file.
Press ‘:q’ to exit the vi program.

Try again, it should work fine now.

To check the permission for the files in the current directory use “ls -l”.

To check permission for a particular file, type out the file name behind “ls -l filname”

File permissiondrwxrwxrwx 2 pi pi

    d – represent the name as a directory.
    – – Regular file or program.
    l – file/dir is a symbolic link.
    s – setuid/setgid permissions.
    t – sticky bit permissions.
    b – driver for storage medium.
    c – driver for communication hardware.


rwx – ‘r’ refers to the read permission
      ‘w’ refers to the write permission
      ‘x’ refers to the permission to execute

1st “rwx” -> owner (‘u’)
2nd “rwx” -> group (‘g’)
3rd “rwx” -> all users (‘o’ or ‘a’)
2 – referes to the number of hardlinks to the file.
pi pi -> Owner:Group

To change the file permission, use the following command,

“chmod a+x filename”
This will add all (‘a’) with executable (‘x’) permission.

“chmod a–x filename”
This will remove all (‘a’) with executable (‘x’) permission.You can also set file permission using binary references (set to _rwxr—–),
command “chmod 740 filename”To change file’s owner and group,
command “chown newuser:newgroup filename”

pi@raspberrypi ~ $ ls -l
drwxr-xr-x 2 pi pi 4096 May 30 04:07 Desktop
-rw-r–r– 1 pi pi 5781 Feb  3  2013 ocr_pi.png
drwxrwxr-x 2 pi pi 4096 Mar 10 18:20 python_games

pi@raspberrypi ~ $ ls -l Desktop
drwxr-xr-x 2 pi pi 4096 May 30 04:07 Desktop

pi@raspberrypi ~ $ chmod a+x ocr_pi.png
pi@raspberrypi ~ $ ls -l
drwxr-xr-x 2 pi pi 4096 May 30 04:07 Desktop
-rwxr-xr-x 1 pi pi 5781 Feb  3  2013 ocr_pi.png
drwxrwxr-x 2 pi pi 4096 Mar 10 18:20 python_games

pi@raspberrypi ~ $ chmod a-x ocr_pi.png
pi@raspberrypi ~ $ ls -l
drwxr-xr-x 2 pi pi 4096 May 30 04:07 Desktop
-rw-r–r– 1 pi pi 5781 Feb  3  2013 ocr_pi.png
drwxrwxr-x 2 pi pi 4096 Mar 10 18:20 python_games

Auto Login (login without being prompt for password). Edit the file /etc/inittab.

Comment away the following line by inserting a ‘#’ in front of the statement.
“#1:2345:respawn:/sbin/getty 115200 tty1”
and insert the following line below it.
“1:2345:respawn:/bin/login -f pi tty1 </dev/tty1 >/dev/tty1 2>&1”

Reboot the system and you should be able to power up and go striaght into the command prompt without being prompt for user ID and password.

pi@raspberrypi ~ $ sudo nano /etc/inittab

#1:2345:respawn:/sbin/getty 38400 tty1
1:2345:respawn:/bin/login -f pi tty1 </dev/tty1 >/dev/tty1 2>&1

Run a script after login (user specific),
by adding the following line to the end of the file /etc/profile (similar to /home/pi/.bashrc)
“. /home/pi/script1.sh”

“script1.sh” will run after the user has been sucessfully login. Local or remote user will get to auto execute “script1.sh” after login.

NOTE!!!
Please ensure to set the file as executable and run the file.

Run a script after the booting process (or within the booting process), but before the login (using service method).

1) Create a script “script2.sh” in the folder /etc/init.d/script2.sh.
“sudo nano /etc/init.d/script2.sh”

2) Make the script executable.
“sudo chmod 755 /etc/init.d/script2.sh”

3) Test the script (service start).
“sudo /etc/init.d/script2.sh start”

4) Test the script (service stop).
“sudo /etc/init.d/script2.sh stop”

5) Register the script to be run at start-up (with default priorities).
“sudo update-rc.d script2.sh defaults”

update-rc.d is a program which mananged the start-up and shutdown using the file /etc/rcX.d (where rcX.d means rc0.d to rc6.d, rcS.d)
You can key in the following command to view the link to your script.
“ls -l /etc/rc?.d/”

6) To remove the script from start-up,
“sudo update-rc.d -f script2.sh remove”
‘-f’ is to force the removal of the symlinks even if the script is still under the /etc/init.d folder. Remember to delete away your script away from the folder /etc/init.d
Note: The command above will only disable the service until the next time the service is upgraded. To enable the service will not be re-enabled upon upgrade, type the following command, “update-rc.d script2.sh stop 80 0 1 2 3 4 5 6”

7) You can also register the services with custom priorities. (you can visit this website)

#! /bin/sh
# /etc/init.d/script2.sh### BEGIN INIT INFO
# Provides: —
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Simple script to start a program at boot
# Description: A simple script which will start / stop a program a boot / shutdown.
### END INIT INFO# If you want a command to always run, put it here# Carry out specific functions when asked to by the system
case “$1” in
  start)
    echo “— script<2> start ———“
    # run application you want to start
    # /usr/local/bin/noip2
    ;;
  stop)
    echo “— script<2> stop ———“
    # kill application you want to stop
    # killall noip2
    ;;
  *)
    echo “Usage: /etc/init.d/noip {start|stop}”
    exit 1
    ;;
esac

exit 0

After testing with various start-up scripts process, I have summarizes the sequence in which the scripts are call up.

— Booting process ——–
    before user login

– Script registered with update-rc.d
– /etc/rc.local

— User login prompt——-
    after user login

– /etc/profile
– /home/pi/.bashrc

— End of start-up process —–
    command prompt

Custom Splash screen
“apt-get install fbi”

Name your image file to “splash.png” and copy to the directory /etc

****encounter problem copying file to /etc directory.***
If the error above is encountered, copy the image file to the user directory instead. Then use “sudo mv” (move file command) to move it to the etc directory.

Edit a new text file “sudo nano”.
Cut and paste the followings,

#! /bin/sh
### BEGIN INIT INFO
# Provides:          asplashscreen
# Required-Start:
# Required-Stop:
# Should-Start:
# Default-Start:     S
# Default-Stop:
# Short-Description: Show custom splashscreen
# Description:       Show custom splashscreen
### END INIT INFO      
do_start () {    
    /usr/bin/fbi -T 1 -noverbose -a /etc/splash.png      
    exit 0  
}    
case "$1" in  
  start|"")  
    do_start  
    ;;  
  restart|reload|force-reload)  
    echo "Error: argument '$1' not supported" >&2  
    exit 3  
    ;;  
  stop)  
    # No-op  
    ;;  
  status)  
    exit 0  
    ;;  
  *)  
    echo "Usage: asplashscreen [start|stop]" >&2  
    exit 3  
    ;;  
esac   
 
:

save the file as /etc/init.d/asplashscreen

make the script executable and install it for init mode:

“sudo chmod a+x /etc/init.d/asplashscreen”

“sudo insserv /etc/init.d/asplashscreen”

Reboot

“sudo reboot “

The custom logo is displayed near the end of the booting process, not at the beginning.

This is followed by a blank screen.
Press <Ctrl + Alt + F2> to return to the command prompt.

pi@raspberrypi ~ $ sudo apt-get install fbi

pi@raspberrypi ~ $ sudo mv splash.png /etc

pi@raspberrypi ~ $ sudo nano

cut and paste, save file as

/etc/init.d/asplashscreen

pi@raspberrypi ~ $ sudo chmod a+x /etc/init.d/asplashscreen

pi@raspberrypi ~ $ sudo insserv /etc/init.d/asplashscreen

pi@raspberrypi ~ $ sudo reboot

Place your favourite wall paper on the desktop.
-> Login GUI Desktop
-> On the desktop, press right click , and -> Select “Desktop Preferences”.
-> Select your favourite wallpaper.

enable sound
sudo modprobe snd_bcm2835
disable sound
rmmod snd_bcm2835

Root access

Some users believe that the root account has a password that they are not aware of. This is not the case. For security reasons, Raspbmc has been hardened by disabling the root account. There is no need to enable the root account in Raspbmc, and doing so increases the likelihood of you causing damage to the system. Instead, the following options are recommended:

• Prefixing the command requiring root privileges with sudo will allow you to run the command as root.
• Alternatively, you can temporarily have root privileges with the command sudo -s

If you truly wish to enable root access so that you can login as root. You can do so as follows:sudo passwd rootYou have now set a root password you can login with.To disable the root account again:

sudo passwd -l root

Changing Raspberry Pi user name (“newUserName”) and password (“abc1234”).

Follow the following procedure,

pi@raspberrypi ~ $ sudo adduser newUserName

Adding user `newUserName’ …
Adding new group `newUserName’ (1004) …
Adding new user `newUserName’ (1001) with group `newUserName’ …
Creating home directory `/home/newUserName’ …
Copying files from `/etc/skel’ …
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for newUserName
Enter the new value, or press ENTER for the default
     Full Name []:
     Room Number []:
     Work Phone []:
     Home Phone []:
     Other []:
Is the information correct? [Y/n] y
 

Give the new user sudo privileges, by editing the sudoers file.
Copy the line with the default user name pi and copy below it. Change the name pi to your newUserName.

After you have finished, key in Ctrl+’x’ then ‘Y’, followed by enter key.

pi@raspberrypi ~ $ sudo visudo

pi ALL=(ALL) NOPASSWD: ALL
newUserName ALL=(ALL) NOPASSWD: ALL

pi@raspberrypi ~ $ logout

pi@raspberrypi ~ $ login

Enter your newUserName and passsword.

Try to see if you can edit the sudoers file. The file can only be edited if it has sudo access privileges.

Delete the line containing the “pi” user, if it is no longer required.
After you have finished, key in Ctrl+’x’ then ‘Y’, followed by enter key.

Delete the old user “pi” account,
or add in option flag “-remove-home” to remove the “/home/pi” directory as well.

The process of changing the Raspberry Pi user name and password is completed.
Reboot the Raspberry Pi for the new user name to take effect. Old user name can no longer be in use.

(method do not work so well. still able login using pi as the user name.)

newUserName@raspberrypi ~ $ sudo nano /etc/kbd/config

BLANK_TIME=0
BLANK_DPMS=off
POWERDOWN_TIME=0

Advance command
– “lsusb” List all the USB peripherals
– “df /” check disk space
– “free” check memory RAM

Linux Files and Directory Structure Reference

Linux Command Reference
– linux_quickref.pdf
– linuxcard.pdf

Add Wifi to Raspberry Pi
Add a Wifi to tap the internet access from your Wifi wireless network.

WiFi dongle keyword
– Edimax EW-7811Un
– Dynamode WL-700N-RXS

Commands Illustration

In order to connect to the Wifi, the first thing you will need is a Wifi dongle for your Raspberry Pi. The following contains the list of Wifi adaptors available that can work with Raspberry Pi.

http://elinux.org/RPi_USB_Wi-Fi_Adapters

In this example, D-Link DWA-123, H/W Ver.: B1, P/N IWA123EU…..B1G

Original setup look like the following,
——————————————————
auto lo

iface lo inet loopback
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp

If you have a DHCP server, change to the following
——————————————————
auto lo

iface lo inet loopback
iface eth0 inet dhcp

allow-hotplug wlan0
auto wlan0
iface wlan0 inet manualdhcp
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp

Photos of SRG 1997

Robot Battlefield, laid with electronics mines. The mine will buzz and light up if it is being knock. Any robot that hit the mine will be out of the game.

Our senior’s robot representing Singapore Polytechnic in SRG 1997. MAR uses 3 infrared sensor, one in the middle and two at the side.

Our senior’s threat from Nanyang Polytechnic. Everybody were surprise by it performance in the 1997 competition. It has strong motor power and speed. This robot is able to complete the race before our senior MAR reaches their 2nd mine. The robot is able to stop quickly and negotiate the mine in a perfect curve in relatively short time, at least 5 times faster than MAR. It is no doubt a clear winner for Robot Battlefield 1997. No robot come close. It seems that they are using gear DC motor. The NYP robot have an array of sensor, sensing the mine from the top. A design that non of us expected. The design is a real genius, because they have break the impression that mines can only be sensed from the side. The position of the sensor is perfect, as mines sensing is very clear cut. This is unlike the side sensors position in MAR and the rest of the robots where sensing is more easily affected by the environment lightings when using infra-red. Looking into the components NYP use and the way the robot operate we guess that they are using PLC controller and a array of infra-red sensor. When the robot senses a defined pattern from the top-down sensor, it will negotiate the mine in a perfect curve close to the mine. Without side sensors to guide the robot, it is unlikely to negotiate the mine in such accuracy and speed. The only explanation for this behavior is that the curve movement profile is being pre-programmed into the PLC. Using PLC is the strength of their team, a group of mechantronic students.

Their design was great, and fit into the game. There is no rules at that time to restrict robot from using top down sensing. Since then, the SRG committee begin to seek new rule to deter new players to adopt such short-cut. The SRG 1998 committee begins to add on new odd shape obstacles prevent the use of such logic control robot. Example of new obstacles like a big/tall/non reflective dust bin in the middle of mine field, with low plank at the corner of the field. This new rules will ensure that the new generation of robot is intelligence enough to negotiate any type of obstacles and maneuver.

This robot from NYP becomes the ultimate aim in our project, to be better than this monster. Our team were looking forward to Robot Battlefield 1998, to fight with NYP robot. We will be following our senior’s robot technology, using direct drive stepper motor (without gear). It was a real challenge.

Robot powered by a 9V battery

This is the robot, I most admire among all robot. If I remember correctly, this robot is from NUS. It is driven by 2 very small tamiya motor with small wheels power by a 9V Alkaline Battery. The whole robot is flat and light like a pizza box, and movement is very swift. Unfortunately there is a problem with their sensing and algorithm which hinder their robot to move between two mines. The robot just move forward and backward very swiftly, just like a mouse who is afraid to move through the mine field. If programmed correctly, this robot could be a winner. The problem might also be their choice of battery. The alkaline battery might not be suitable to run high current application. This may affect the power stability, which affects their digital logic circuitry. It will be extremely difficult to troubleshoot software if the bug is partly contribute by the hardware. In my heart, this NUS robot will always be special for it’s performance in speed and energy efficient.

This is one of the robot using ultra sonic sensing. The sensor is enclose behind the casing. We are very aware that only this type of sensor at that time, can be mounted in this manner. We were trying very hard to analysis all possible threat for Robot Battlefield 1998.

Some other photos taken. It is a norm in SRG competition, that most IC chips are blank off, especially the important ones. This deter the competitor to learn more about their robotic system or to steal technological ideas. It is easy to learn about robot capability by observing their circuits, mechanical and sensing technology.

Spotronic Robot is still under development.

Motivate by my previous work in working on a mine avoidance vehicle, representing Singapore Polytechnic for the Singapore Robotic Games 1998. It is a new robotic event, and we are only the second batch of student competing in the event call “Robot Battlefield”. It was a very exciting moment in my life that no amount of words can described that feeling. The competition barely a minute in the battle field determines our one and a half year worth of effort.

The happiest moment, our commitment have won us a Gold Award in the competition. The award is won by my team namely, project leader Chew Chuen Hee (hardware motor), Lee Chin Kwang (firmware sensor and decision control), Pang Sze Hsin (hardware electronics) and lastly me Lim Siong Boon (motor driver firmware).

The rules of Robot Battlefield can be found in the SRG 1998 website or a copy of the rules I saved from the website. A lot of  changes to the rule have been make for Robot Battlefield 99. Part of the changes are resulted from some frustrating incident that occur during our competition in 1998. I shall touch further on this in future.

The following are some of my design work regarding the robot sensor positioning. It has never been implemented because of the demand in writing motor driver software. I am suppose to handle all the software coding for the whole robot. In the end, the demand in writing the motor control algorithm has taken me the whole one and a half year of our project schedule. It was quite complex to me at that time because it is not easy to debug the mechanical performance in real time. Electrical problem may surface when the robot operate by itself on the floor. Switches get trigger due to mechanical vibration when the robot travels. These are the kind of unforeseen bugs makes our debugging task extremely difficult. The task of writing sensing algorithm is eventually taken over by my team mate Chin Kwang who is in charge of sensor design.

Mine Avoidance Vehicle project report. (13.4 Mb)

My motor driver software for motorola microcontroller MC68HC705C8CS (commonly known as 6805), master and slave operation for the left and right stepper motor. The file are in asm machine language. Although I have written a lot of comment in the source code, it is now meaningless to me. I hardly remember that they were my own codes. The concept is still clear in my mind, how the two stepper motors are operated. The robot uses 3 microcontroller because we have meet the speed limitation in motorola 6805. A single 6805 chip is too slow in supporting our target robot speed at 2 meter per second. We have suggested switching to a more powerful microcontroller but was rejected by our supervisor as he is afraid that the learning curve for a new controller will be long. In the end, we had all agreed to implement 3 microcontroller to control the robot. One main controller for sensor algorithm, one master and slave microcontroller for left and right motor. Initially I have great doubt that individual controller for each motor will work. There might be synchronizing problem which affect the robot from traveling straight. Eventually after the first prototype, it seems working very well and the problem is in fact negligible. There was nothing to worry about after all.

My team mate Sze Hsin, and Chin Kwang. We take some photos during SRG 1997.

Our team leader Chuen Hee (Mechanical, Electronics hardware), Chin Kwang (Sensor, Robot algorithm firmware), Sze Hsin (Electronics hardware, PCB), Siong Boon (Me, Motor driver firmware & software tools).

Too bad that these are all the photos I have on hand. Furthermore they are blur. If you have more photos to share for SRG 1998, 1997, 1999, please forward me your collection. I will be excited to receive these precious.

Pinky (left), Brain (right).

Pinky & the Brain, the name has a very symbolic meaning. To conquer the world, the dream of Pinky and the Brain, which is what we want our robot to achieve.

We have created two similar robot for the competition. It is the cutest name we come up with. I love it. One robot, we call it “Pinky”, and the other one ” Brain”. Combine together, they are call “Pinky and the Brain“.

The saddest thing is that I didn’t keep any of the photos we had. I cannot forgive myself for not taking any pictures of our champion robot. It is one of the regret of my life for not taking any photos. The only traces of the robot we have created were our project report, certificates and the only website link on SRG 98.

Anyone of you out there, have document or picture for SRG 1998, please let me know. I am eager to get in contact with you. If only our competitor see this, I am sure they have our Pinky and the Brain photos taken.

Our developed robot is far superior from our senior. I forgot how we eventually agreed to join into this robotic game category. What we observe in our senior’s demonstration, there are plenty of opportunities for improvement. Our senior’s robot has limited sensor capability and their robot speed and movement is rather slow. For each object blocking their robot path, the robot execute a stop and do rotation, moving forward and rotate movement until the robot negotiated the obstacle “mine”. This wasted a lot of time and speed as time is required to do acceleration and braking.

My job is to write a motor driver firmware to provide ease of control for our main software (sensor algorithm), at the same time control our stepper motor to speed and precision. To improve our robot speed in the competition, we cannot afford to stop the robot. The turning have to be made immediately when obstacle is detected. The motor driver allows full speed control and full degree of left, right turn options. Efficient acceleration and de-acceleration of both the left and right motor are taken care by the driver controller. This ease processing power from the sensing controller which is programmed by my team mate Chin Kwang.

I will write more of this topic in future.

written by Siong Boon, 29 Nov 2005

I forgot to mount on another PCB circuit which is the motor and LCD driver. The PCB board shown on the photos consist of the logic circuits. They uses less power and the digital control is run by my favourite microcontroller from Microchip, PIC16F877A.

The robot is in-completed as some of the electronics module is under research phase.

1) Power regulator, DC to DC

2) Wireless FM Transceiver

Other module involved and does not need further improvement are as follows,

1) Microcontroller PIC16F877

2) DC Motor driver L6203

3) Serial communication interface

4) LCD control

I want to make a good robot. Although I had purchase a DC to DC module to supply my electronics, I insist on robot completion using minimum funding. The DC to DC research is completed but I had yet put onto my robot. The DC to DC cost half the price of the module I brought and it provides me with the experience for future higher current application.

The next module I lack of is the wireless transceiver, which I never successfully have it working until recent FM transceiver research. The previous attempt fail, until the discovery of implementing an encoder and decoder for the data transmission. Finally my dream of a remote control robot is on the right path. Parallel digital bits transmission is tested to be working fine. The next step will be to try out serial communication through the transceiver.

Will update on my robot again once I have completed my documentation.

written by Siong Boon, 29 Nov 2005

1. RFID Introduction

Having the Right Mindset for RFID technology.

RFID is known as Radio Frequency IDentification. The technology is able to wireless-ly picking up information from a RFID tag which can be embedded onto most object. Fast and reliable. RFID has helped to rise up our productivity.

The process starts with the RFID reader transmitting power and command wireless-ly. The RFID tag intecept the energy to power up itself. It starts to decode the request commanded and transmit the result back to the RFID reader. All these happen instantly with microseconds.

Many of the old technologies (bar-code, magnetic stripe, smart card) can be replaced by RFID system, but rate of adoption rate is slow. Examples of applications that the RFID have completely taken over are, security door access system and transportation payment card. Comparing RFID over the old technologies, it is perceive to be more expensive. The technology do has its advantages and disadvantages, which is why not all applications use RFID.

People likes to compare RFID to a bar-code system which is a cheaper alternative. The fact is, RFID tag will never be as cheap as a printed bar-code. It is more complex than bar-code. No matter how big the production volume will be, it will not be cheaper than the bar-code. Using a RFID to perform barcode application is analogy to hiring an engineer to do simple office cleaning work. No company would be in the right set of mind to invest in a expnsive solution to replace what a cheaper solution would solved.

People also think of RFID technology as a solution. RFID unique and good, but it can only solve part of the problem that we are facing in our life. You can analogy it to a very good engineer that you have hired. He/she has all the skills and know-how to design a quality system that no one else can, but there are no proper tools and equipments provided. Only a broom and a dustpan is provided. The engineer will be as good as a cleaner. RFID is designed to solve certain problem very efficiently. By itself, it cannot do any much. It has to work hand in hand with another good technology.

RFID has its own unique properties that no other technology is able replace it completely. Applying RFID technology to its advantage, to the right application will be the key to success adoption. If you want RFID system to be successful, you cannot think using a bar-code brain.

This site is dedicated to understand more about the properties of RFID technology, hence allowing us to apply its unique leading edge where no other technologies can replace. The focus will be mainly in the RFID for ISO/IEC14443 (HF 13.56MHz RFID system) which has a near perfect characteristic for interaction between humans and object; and also information on ISO/IEC18092 (NFC protocol implementation) which is the new trend on applying RFID technology. With the growing number of NFC mobile phones being launch, we can clearly see that the industry is committed in making our life more productive.

Let us start by a simple overview of various technologies that is related to RFID. We can easily see the advantages/disadvantages that the RFID can have in the application of tagging and identification.

Comparison chart of tagging/identification technologies

Description				Form factor can be like like a thicker credit card
Technology name	LF RFID (LF Passive)	HF RFID (HF Passive)	UHF RFID (UHF Passive)	Active RFID Tag (UHF Active)	2D Barcode	Barcode	Smart Card	Magnetic Stripe	Light	Sound
small in size
conceal easily
contain more information
attach to odd shaped object
attach to object with metal surface or liquid content
store information
durable
passive (no need battery)
contactless
no need to be line of sight
retrieve data fast
secured communication
low cost
far reading distance
simple to manufacture
frequency	<135KHz	13.56MHz	868-950MHz	433-5.8GHz
read distance	low 0-15cm	low-medium 0-1.5m 0-15cm (NFC)	far up to 10m	very far more than 10m to km
data rate	4-8kbps	6.7-848kbps

 Selecting guide your RFID technologies. Click here -> rfid-guide.pdf

2. RFID Tags

HF RFID tag 125KHz / 13.56MHz	UHF RFID tag 860 – 960 MHz / 2.4Ghz

Click to enlarge the picture.

Basic RFID Tag

RFID tag, is also known as RFID Transponders. The tag is make up of three basic components. An IC chip, an antenna or coil, and a substrate that holds the chip and antenna/coil together.

The picture on the left shows two typical tag design. The one on the left is a coil design. It is mean for LF/HF RFID tag (low/high frequency) that operates in a low frequency range. The tag uses induction method as a means for power and communication. The UHF RFID tag (ultra high frequency) on the right uses a dipole antenna design. The tag uses RF transmission (radio frequency operating at a much higher frequency) method to obtain its power and achieve communication.

Higher frequency tag is able to transmit information faster, and need less energy to receive/transmit information compare to a tag that uses lower frequency; lower frequency takes more time. Antenna helps to transmit the signal can be smaller at higher frequency. With the signal transmitting out of the antenna, tag can be read at a further distance away.

At this stage in time, you may think that a UHF tag is better than a HF tag. You can be right and wrong. A tag that can be read at a far away distance can be good. The same property will not be good if you need to get hold of a specify tag but end up with all the rest of the tag nearby. There is little value in defining the good and bad. What is more important, is understanding the property of what it can or cannot do, and apply its properties to its advantage. This depends mainly on the application.

For the application of tagging an object, I have valued HF tags more than the other alternative technologies. Passive RFID tag using HF or NFC has a higher potential in solving problems relating to interraction betweeen living things and physical object. This which will be further presented as another topic in another site.

This is a finger that I have downloaded from the internet. Notice the black square dot on the middle of the finger. That is the RFID transponder IC chip which can be found on a RFID tag. You can hardly see it.

IC chip for RFID tag

The IC chip on the RFID tag is very very small; not much bigger than a gain of sand (see photo on the left). This makes the tag small enough for a lot of purpose. This IC contains memory which can store information. The cost of the chip is proportional to the memory size and functional it has. The IC chip needs power to operate. It will get its power from its antenna. The tag’s antenna will capture the energy transmitted by the RFID reader. The RFID reader will generate the RF energy from its own antenna when a read command is initiated.

There is a limit distance in which the antenna can effectively capture the RF energy for powering up the tag. This distance will depends on the transmitting power from the RFID reader, as well as the size of the tag’s coil. The bigger the coil on the tag, the further the distance. As a rule of thumb, a bigger tag is expected to achieve a further read distance than a smaller tag..

**pic of transmitting energy from induction stove, RFID reader. Coil with LED. big tag further distance. higher power further distance

When the tag received enough power to operate, the IC will immediately power up, and response to the command from the RFID reader. The tag will usually read the binary information contains in its memory and send them back to the reader. The basic form of read information will be the tag identification number. If the tag contains additional user data, the reader can issue command to read them all. All these process happens within micro seconds.

RFID tag is essentially similar to a memory card. Similar to the flash memory card that we have been using for our digital camera, the RFID tag is using wireless power/communication, and has much less memory. The memory available can be as little as a few bytes to store the tag ID, to about 8Kbyte to store other user’s data. Each alphabet letter takes about 1byte of space, so a 8Kbyte memory can store about 8000 characters. The higher memory capacity tag will usually cost a bit more.

The LF RFID tags that I have seen can only be read. HF tags can be read/write. It is also possible to protect the tag from data writing. Some IC chip is able to kill the tag, therefore prevent a read from the tag, rendering the tag useless.

Depending on the chip, tags can be pre-programmed during the manufacturing to contain the same or unique ID no. (identification number). An unique ID no. for each tags will enable the reader to differential the multiple tags read.

LF and HF tags uses induction method and has a short reading distance <10cm. UHF tags can go as far as 10m. The distance will varies with varies RFID reader’s transmitting power and antenna/coil size. A bigger size antenna will usually have a longer read distance.

	Ferrite raw material in powder form
	Ferrite bead commonly used for EMI on cable.
	Ferrite sheet is form like a rubber mat and can be cut and place behind the RFID tag to improve readibility.

Fig 1. Magnetic field pattern of a typical RFID operation.
Fig 2. Magnetic field interference when RFID tag is stick close to a metal surface.
Fig 3. Improve magnetic field operation with a ferrite sheet between the tag and metal surface.

Fig 4. Cross section of the magnetic field detected

RFID operation with metalic or liquid objects

RFID has difficulty operating near metalic, liquid object (water bottle/ human body). Induction field around the tags will be collapse by these object. A minimum gap away from such object is required for proper operation. Metal surface can block/reflect RF signal, causing distortion to the signal, making it difficult to read the tag. There are special anti-metal tags (RFID Metal Pad) that allows RFID to operate under such tough condition. These tags are padded with a sheet of ferrite material behind the tag. The sheet actually forms the gap between the tag and the metal surface, allowing the tag to be read through the RF. The ferrite is itself a RF friendly material which permits the RF & field to sustain. With this padding, the tag readability can be improve slightly.

Ferrite sheet is available from:

TDK, FLEXIELD material

MARUWA, FLEX-u sheet

Active RFID tag

Active RFID tag with sensor attached

Active RFID tag with built-in sensor

Active RFID tag (sef powered, usually a battery) operates like a typically electronic transceiver device. Reading distance is a lot further than a passive RFID tag (not self power). The operations is similar to a passive tag where the reader will be able to retrieve the tag information when it is near enough. Some call the tag a signal beacon, where the tag keeps sending signal out. The tag can be read at a much further distance. This is because it has its own power source and do not need to harvest from the reader.

There are active tags that have built in sensor. The temperature/humidity sensor for example, will be operated by the RFID tag and send back the temperature read back to the reader. The battery usually last quite sometime, but it will definately need replacement one day.

Buy your NFC Tag Now at the PIC-store

Three typical standard among RFID tags
– LF tag (Low Frequency 125KHz) ISO11784 / ISO11785
– HF or NFC tag (High Frequency 13.56MHz) ISO/IEC 14443
– UHF tag (Ultra High Frequency EPC Class 1 Gen2)

Good RFID tag reference information, http://www.gorferay.com

RFID tag IC chip and standard

When dealing with RFID tags or reader, we will often come across various ISO standards. These ISO defines a common standard for the hardware or software to interact with one another.

The LF RFID (125Khz), ISO11784/ISO11785 is a common standard.

For UHF RFID, it is EPC Gen2 or EPCglobal UHF Class 1 Generation 2

For HF there are standard ISO15693, ISO14443 and ISO18092 (NFC). For NFC, we will focus on ISO14443 and ISO18092.

Some notes regarding NFC standards or ISO18092 (from website http://users.skynet.be/marc.sel/index-MTC.html)

In transport applications, cards suffer from daily use, for which reason contactless cards are preferred. Contact cards are more prone to hardware wear-out, hence contactless cards are better suited in the transport sector. This led to the creation of the RFID standard, ISO 14443, composed of 4 parts. It operates in the non-licensed 13.56 Mhz band. As there were two main “competitors”, there are two substandards:

• ISO 14443 type A (origine: NXP)
• ISO 14443 type B (origine: RATP)

Later under impetus from Sony, the NFC standard was established as ISO 18092. It’s a backward compatible extension to RFID, mainly aiming at use in mobile phones. It’s was actually proposed as ISO 14443 type C by Sony, based on FeliCa. It’s used e.g. in the Hong Kong Octopus and Singapore EZ-link systems. It did not make it to the 14443 standard, but came back as NFC.

Article for ISO/IEC 14443

• ISO/IEC 14443-1:2000 Part 1: Physical characteristics
• ISO/IEC 14443-2:2001 Part 2: Radio frequency power and signal interface
• ISO/IEC 14443-3:2001 Part 3: Initialization and anticollision
• ISO/IEC 14443-4:2001 Part 4: Transmission protocol

Mifare Tag ID issues (tag ID unqiue?)

Mifare name comes from the “MIkron FARE Collection System”. Mikron was aquired by Philips (NXP) in 1998. Given the Mifare Classic tag ID of 4 bytes, will the tag ID run out of unique ID?

• Mifare RFID Tags, an FAQ on ID Issues.pdf
• AN10927, MIFARE and handling of UIDs.pdf
• Mifare RFID tag & reader IC comparison chart.pdf

RFID tag/transponder IC manufacturer

	NXP Semiconductors, Mifare RFID transponder IC manufacturer
	Alien Technology, has many UHF tags
	ST microelectronic
	EM Microelectronic
	Texas Instruments
	Legic
	Inside Contactless
	Atmel
	Siemens (infineon)
	Innovation Research & Technology
	ISSI

Common RFID tag packaging

**Packaging (find chinese terms)
– inlay (wet/dry)

Reference:
http://www.skyrfid.com/RFID_Tag_Inlays.php

Inlay (dry)

Dry inlay is the fundenmental building block for RFID tag. They are usually be further packaged into RFID tag products. The term “dry” means that it does not have adhesive on it’s tag surface. The inlay can comes in roll or sheet form.

Common size:
35x35mm
43x26mm
50x30mm
85.5x54mm

Inlay layer and thickness
	Layer: IC:75um-150um Al(TOP)30um PET:38um AL(Bottom):10um

Layer within a RFID card
	Different layer of a package RFID card. The RFID inlay is sandwiched between the PVC (Polyvinyl chloride) and next with printed PET/PVC (polyethylene terephthalate) finishing.

Inlay (wet)

Wet inlay means that the inlay has adhesive on one of its side. The tag will be attached to a pressure sensitive liner base.

– sticker label

IDCard/Badge

These are hard PVC card about 1mm thickness. The card printing can be customised. There is also a special printer that prints on these plain tags.

– PVC/Plastic card
– glossy, matt paper

ezlink using CEPAS card

FlashPay using CEPAS card

Visa Paywave

www.octopus.com.hk

Payment Card (Singapore)

Ezlink, based on the Sony FeliCa smartcard technology

Flash Pay

payWave

CEPAS = ISO/IEC 14443-4 + ISO/IEC 7816-4: 2005

– Singapore Standard, specification for contactless e-purse application

Octopus card, based on the Sony FeliCa smartcard technology

base on MIFARE DESFire EV1 card

RFID Tag manufacturer

	HID
	Intermec
	Avery Dennison
	Alien Technology, has many UHF tags

4. RFID Reader

RFID reader is getting more and more common. Nowsaday Windows & mobile phone OS has built in driver treating RFID reader as a standard device.

USB RFID reader kit

RFID Reader manufacturer

	HID
	Intermec
	Alien Technology, has many UHF tags
	Motorola

5. NFC

NFC (Near Field Communication)

NFC phone to phone,

Phone to RFID tag

NFC currently use for Payment, transportation payment.

Instantly access to webpage,

Instant bluetooth/WiFi connectivity.

Reference:

– NFC Tags A technical introduction, applications and products, R_10014

– Understanding the Requirements of ISO IEC 14443

– MIFARE Ultralight as Type 2 Tag, AN1303

– NFC Type MIFARE Classic Tag Operation, AN1304

– MIFARE Classic as NFC Type MIFARE Classic Tag, AN1305

– MIFARE Type Identification Procedure, AN10833

6. Card Reader IC

13.56MHz RFID card reader IC

Getting to understand RFID was quite a confussing experience, with so many technical jargon. This was the reason why this website is setup; to sort out all the technical stuff into bits and pieces.

Card Reader is another interest topic to looking. A card reader helps to read out the information in a tag. An RFID reader is not a different device to understand, but not the card reader.

What is the difference between an RFID reader and a card reader? The RFID reader reads RFID tag. There are many variety of RFID standards in the industry. This means that there are also many type of RFID reader to read each type of card. (The type of cards was already presented above).

The variety of reader is going to make things complicated for developer who are developing application. This call for an universal solution known as ISO 7816. This is a standard defined for interfacing application with all smart card devices.

From what I read in the internet, this standard goes way back to the smart card technology. The smart card unlike RFID card is using wired communication to read the information on the card. You can identify it by the contact pins as shown in the following pic.

It is possible that a card has both the smart card as well as RFID card.

With the introduction of new form of card like RFID, the ISO 7816 evolve over time. ISO 7816 defines a standard interface for the card reader. The communication standard to a card reader device becomes a standard.

Article for ISO 7816 (specification for interfacing with card reader)

– AN4029, The DS8007 and Smart Card Interface Fundamentals

PCSC Personal Computer Smart Card is a standard framework for Smart Card access on Windows Platforms. This will make the job easier for application developers to interface to a card reader. To the developer, all card reader seems to work the same way.

The window operating system will automatically detects.

Interoperability Specification for ICCs and Personal Computer Systems

– PCSC_Part1, Introduction and Architecture Overview.pdf.pdf
– PCSC_Part2, Interface Requirements for Compatible IC Cards and
Readers.pdf
– PCSC_Part3, Requirements for PC-Connected Interface Devices.pdf
– PCSC_Part4, IFD Design Considerations and Reference Design
Information.pdf
– PCSC_Part5, ICC Resource Manager Definition.pdf
– PCSC_Part6, ICC Service Provider Interface Definition.pdf
– PCSC_Part7, Application Domain and Developer Design
Considerations.pdf
– PCSC_Part8, Recommendations for ICC Security and Privacy
Devices.pdf

My card reader

ACR122 NFC card reader from ACS.

Documentation
– PPE_ACR122, presentation.pdf
– API_ACR122U, Application Programming Interface.pdf
– TSP_ACR122U_v2.5, Technical Specification.pdf

Win7 64bits driver
– DIG_ACR122, Driver Installation Guide.pdf
– ACR122U_MSI_Winx64_1120_P

This is the first NFC card reader that I have brought. I have purchased this reader without any development kit, and was struck wondering how I can read a RFID tag without any software.

After understand about ISO 7816 and PCSC, I managed to find a number of free software that can communication with this NFC card reader. They are designed to work with PCSC compliants card reader.

– SCardToolSet, Smart Card ToolSet PRO v3.4
– sq2075-ba, SpringCard PCSC Diag
– online PCSC card reader program

The software are able to detect my card reader immediately. When my RFID tagis placed on the reader, the software detects it and display the tag information.

The very first unqiue string that was captured when I read the RFID tag is this string call ATR (Answer To Reset). It is a very weird name, because I was thinking that this should be the unqiue ID of the RFID tag. No it is not. This ATR string (as defined in ISO 7816) is telling us how we can communicate with the current tag found on the card reader.

This is the ATR string that I read when the tag (picture on the left) is on the reader

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68

So what does this hexidecimal string of number means?

With this ATR string provided by my card reader, I will know more about the RFID tag that I am actually dealing with. The RFID tag that I have place is using the Mifare Ultralight tag’s IC chip. ISO14443A is use for communication between the reader and the tag. The rest of the information seems not so useful to me.

To communicate with the card reader we will have to send a string of bytes to the card reader. The data format to communicate with the reader is known as APDU (Application Protocol Data Unit).

I have refered to the API (Application Programming Interface) datasheet provided by the card reader manufacturer. The first command to try is the command “Get Data”. The command will fetch the unique ID of the tag.

data send -> FF CA 00 00 04
where CA is the <Get Data> command.

The following response bytes are received.

data received <- 04 06 CD E2 90 00
where “90 00” is the response code (The operation completed sucessfully)
” 04 06 CD E2″ is the unique tag ID.

Next I tried to get the card reader firmware version.

data send -> FF 00 48 00 00
data received <- 41 43 52 31 32 32 55 32 31 30

The data received is “ACR122U210” in ascii format

Another Mifare Ultralight tag1 was read for its ATR and tag ID

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 04 AA 2C 79 90 00

Another Mifare Ultralight tag2 was read for its ATR and tag ID

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 04 2D 44 79 90 00

Reading Singapore Ezlink card (CEPAS card)

Next I tried another RFID tag. Our Singapore Ezlink card, which stores transportation logs in CEPAS format.

ATR = 3B 8C 80 01 50 72 23 AA 5E 1C 2D 94 11 F7 71 85 4F

When the tag is removed and placed on the reader again, the ATR string changes. This is unlike the previous tag where the ATR will remains the same for the same tag.

ATR = 3B 8C 80 01 50 21 0A 96 CF 1C 2D 94 11 F7 71 85 98
ATR = 3B 8C 80 01 50 B5 AE 55 A7 1C 2D 94 11 F7 71 85 03
ATR = 3B 8C 80 01 50 6D 83 67 F0 1C 2D 94 11 F7 71 85 93

The ATR tells us that it uses the application identifier 0x50. I don’t know what it means.

Next I proceed to send read tag ID command.

ATR = 3B 8C 80 01 50 5D 83 48 22 1C 2D 94 11 F7 71 85 5E
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 5D 83 48 22 90 00

ATR = 3B 8C 80 01 50 FE 15 0F A4 1C 2D 94 11 F7 71 85 AA
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- FE 15 0F A4 90 00

The tag ID changes with the ATR string. A closer look review that the tag ID is the same data as the substring in the ATR.

A DESFire EV1 card ATR string is unexpectedly short.

ATR = 3B 81 80 01 80 80

The ATR string remains the same when the tag is

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 84 D9 62 65 A2 3C A7 C8 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- F3 A2 3C CC 2A 89 6E 51 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- EB F4 A2 15 88 41 0C 3C 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- FF 15 CD 6C 73 F0 28 D5 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- BA B1 7A 2A 9C 23 C8 B7 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

Load
APDU send -> FF 82 00 00 06 FF FF FF FF FF FF
APDU received <- 90 00 (90 00 means ok)

Read binary Page 0x04, 4 bytes
APDU send -> FF B0 00 04 04
APDU received <- 31 39 30 39 90 00

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- 31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E 90 00 (each page consist of 4 bytes)

Read binary Page 0x00, 256 bytes
APDU send -> FF B0 00 00 FF
APDU received <- 63 00 (no information given)

Read binary Page 0x01, 256 bytes
APDU send -> FF B0 00 01 FF
APDU received <- 63 00 (no information given)

Read binary Page 0x00, 16 bytes
APDU send -> FF B0 00 00 10
APDU received <- 04 06 CD 47 E2 87 28 81 CC 48 00 00 00 00 00 00 90 00

Read binary Page 0x01, 16 bytes
APDU send -> FF B0 00 01 10
APDU received <- E2 87 28 81 CC 48 00 00 00 00 00 00 31 39 30 39 90 00

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- 31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E 90 00

Read binary Page 0x08, 16 bytes
APDU send -> FF B0 00 08 10
APDU received <- 20 4C 49 4D 00 00 00 00 00 00 00 00 00 00 00 00 90 00

Read binary Page 0x0C, 16 bytes
APDU send -> FF B0 00 0C 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00

Read binary Page 0x10, 16 bytes
APDU send -> FF B0 00 10 10
APDU received <- 63 00 (no information given)

Read binary Page 0x10, 1 bytes
APDU send -> FF B0 00 10 01
APDU received <- 63 00 (no information given, memory bank stop at page 0x0F)

Read binary Page 0x0F, 1 bytes
APDU send -> FF B0 00 0F 01
APDU received <- 00 90 00

Read binary Page 0x0F, 16 bytes
APDU send -> FF B0 00 0F 10
APDU received <- 00 00 00 00 04 06 CD 47 E2 87 28 81 CC 48 00 00 90 00 (16 bytes of data can be read from the last page 0x0F. There is no page 0x10, the data is actually from page 0x00)

Mifare tag memory data from page 0x01 to 0x0F read:

04 06 CD 47 E2 87 28 81 CC 48 00 00 00 00 00 00
31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E20 4C 49 4D 00 00 00 00 00 00 00 00 00 00 00 0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Total memory is 64 bytes.

Ascii message contains “1909–SIONG BOON LIM”

This tag is a Mifare Ultralight tag with memory of 64 bytes

byte 00 SN0 (serial number)
byte 01 SN1 (serial number)
byte 02 SN2 (serial number)
byte 03 BCC0
byte 04 SN3 (serial number)
byte 05 SN4 (serial number)
byte 06 SN5 (serial number)
byte 07 SN6 (serial number)
byte 08 BCC1
byte 09 Internal
byte 10 Lock0
byte 11 Lock1
byte 12 OPT0
byte 13 OPT1
byte 14 OPT2
byte 15 OPT3
byte 16 Data0
….
….
byte 64 Data47

Reading the tag ID full 7 byte serial number
APDU send -> FF CA 00 00 07 (read full tag ID 7 byte)
APDU received <- 04 06 CD E2 87 28 81 90 00

Actual Tag ID is in the following sequence (high address, high byte),
SN6 SN5 SN4 SN3 SN2 SN1 SN0
 81  28  87  E2  CD  06  04

Try read tag ID 8 byte, not a correct read
APDU send -> FF CA 00 00 08
APDU received <- 04 06 CD E2 87 28 81 90 90 00
Able to read a 0x90 data for the last byte but this data cannot be found within the tag’s memory.

Read binary Page 0x29, 4 bytes
APDU send -> FF B0 00 29 04
APDU received <- 00 00 00 00 90 00 (ok)

Read binary Page 0x2A, 4 bytes
APDU send -> FF B0 00 2A 04
APDU received <- 63 00 (not ok)

Total available page is 42 from 0x00 to 0x29.
Total memory is 42 pg x 4 bytes = 168 bytes

Read binary Page 0x2B, 4 bytes
APDU send -> FF B0 00 2B 04
APDU received <- 00 00 00 00 90 00 (ok)

Read binary Page 0x2C, 4 bytes
APDU send -> FF B0 00 2C 04
APDU received <- 63 00 (not ok)

Total available page is 44 from 0x00 to 0x2B.
Total memory is 44 pg x 4 bytes = 176 bytes

Reading tag ID
APDU send -> FF CA 00 00 04 (read tag ID, 4 bytes)
APDU received <- 2B 2C 1E 95 90 00

APDU send -> FF CA 00 00 07 (read full tag ID, 7 bytes)
APDU received <- 2B 2C 1E 95 07 00 00 90 00

APDU send -> FF CA 00 00 08 (try read incorrect tag ID length)
APDU received <- 2B 2C 1E 95 07 00 00 90 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 63 00
Reading from location fails

Authentication with a type A (0x60), key number 0x00 for memmory block 0x04
APDU send -> FF 86 00 00 05 01 00 04 60 00
APDU received <- 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read again ok.

Card is removed and place back on the reader.
Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 63 00
Reading from location fails. The card will need to go through authentication again.

Authentication with a type A (0x60), key number 0x00 for memmory block 0x04
APDU send -> FF 86 00 00 05 01 00 04 60 00
APDU received <- 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x05, 16ytes
APDU send -> FF B0 00 05 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x06, 16ytes
APDU send -> FF B0 00 06 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x07, 16ytes
APDU send -> FF B0 00 07 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x08, 16ytes
APDU send -> FF B0 00 08 10
APDU received <- 63 00
Reading not ok.

Read from block 0x03, 16ytes
APDU send -> FF B0 00 03 10
APDU received <- 63 00
Reading not ok.

Authentication on block 0x04 can only allows reading of data for block 0x04 to 0x07 (which is on the same sector 1) for as many times without the tag leaving the card reader. Memory block 0x03, 0x08 cannot be read.

Mifare 1K tag memory block
Sector 00, Block 0x00 – 0x03 (16 bytes/block)
Sector 01, Block 0x04 – 0x07
….
….
Sector 14, Block 0x38 – 0x3B
Sector 15, Block 0x3C – 0x3F

Authentication with a type A (0x60), key number 0x00 for memmory block 0x3F
APDU send -> FF 86 00 00 05 01 00 3F 60 00
APDU received <- 90 00
Ok, reading the last block.

Read from block 0x3F, 16ytes
APDU send -> FF B0 00 3F 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Authentication with a type A (0x60), key number 0x00 for memmory block 0x40
APDU send -> FF 86 00 00 05 01 00 40 60 00
APDU received <- 63 00
Not ok. (out of the 1K zone)

Reading Mifare 4K is the same as Mifare 1K. Only the memory map is different.

Read binary Page 0x00, 16 bytes
APDU send -> FF B0 00 00 10
APDU received <- 04 AA 2C 0A 79 62 02 80 99 48 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x08, 16 bytes
APDU send -> FF B0 00 08 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x0C, 16 bytes
APDU send -> FF B0 00 0C 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x10, 16 bytes
APDU send -> FF B0 00 10 10
APDU received <- 63 00 (not ok)

Data Memory in the tag
04 AA 2C 0A 79 62 02 80 99 48 00 00 00 00 00 00
FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Seems like no NFC data inside.

Any material can influence magnetic, it is a matter of the intensity.

Strong Magnetic Materials (Ferromagnetic materials)
– Iron
– Nickel
– Cobalt

Not Strong (Paramagnetic materials)
– Aluminum
– Magnesium
– Platinum

Weak (Diamagnetic materials)
– Copper
– Lead
– Sliver

KRF-DTR401 FM Transceiver

After working successfully on my first transceiver, I started souring for other transceiver for research purpose. It is at that time, I have noticed that some of the transceiver have similar specification. The circuit layout is compared and found very similar in various area. After further investigation, the IC chip they used in the PCB is the key to building this transceiver.

The circuit is simple and is mainly operated by the IC on the PCB board. It is actually originated from nRF401 IC from Nordic Semiconductor ASA.

The testing of the RF module couldn’t have taken place without the development of my own dc-dc converter. Commercial module is available but cost is high. Voltage regulator is necessary for most electronics circuits project. Therefore learning to build a dc-dc circuit from discrete components is worth the effort.

Schematic for Data Encoder MC145026, Decoder MC145027.

2006-03-xx: There is a problem that was found during the attempt to use this design on my robot. The wire link from the transceiver and the decoder IC cannot be too far apart. Data error rate seems to be very high, and reception is very poor. It could be due to the weak signal strength, which should be resolve by using a digital buffer. The signal is digital from the output of the transceiver. If it is a transmission issue, then it will be quite difficult to troubleshoot without proper equipment.

433Mhz AM Transceiver

433Mhz Transmitter

433Mhz Receiver

Dated: 2012-05-18

There are many RF transceiver module in the market. When the transmitting distance is a concern, my preference will be transceiver in the range of 80 ~ 500Mhz. Wireless module in the gigahertz range can achieve higher data transmission rate but transmission distance will be shorter, especially when deployed indoor.

433Mhz is a good choice for distance communication. These pair of wireless module form a one way communication. You can get these from PIC-STORE. Working in this frequency range, the antenna may be slightly long. The antenna can be just a simple wire. The interfacing can be easy as what is presented in this experiment, but in order to transmit useful information, data modulation will be recommended. Data modulation is a process which changes the physical signal to another format so that it is less prone to noise/error and is easier to decode.

The data rate for such a wireless setup is quite low, about 1~4Khz, but it is enough for most of the simple applications.

I have managed to setup a simple transmitter and receiver circuit. The schematic is attached below. The objective is to understand how the signal looks like. This will allows us to understand and make use of these raw transmitter/receiver for sending useful data. It is not so direct using these raw module. Pre-processing will be required in order to send information.

The picture shows two portion of the circuit. The left side is the 433Mhz transmitter, and a push switch (black). The right portion is the receiver which consist of the 433Mhz receiver and a LED indicator.

This is the schematic details of the simple setup. When the button is not pressed, the transmitter will send out logic 0. When the button is pressed, it will transmit logic 1.

The receiver will have a LED indicator which allows me to see the response when the button is pressed. When the receiver’s data output is low, the LED will light up. When it is high, the LED will be off.

I have attached a video of how the response is when the button is pressed.

– Video of this setup. MVI_0275.AVI

In the video, you will be able to see that when the switch is not pressed (logic 0), the LED will blink continuously. When the button is pressed (logic 1) the LED will constantly light up (low output).

How the actual signal looks like? I managed to probe the data in of the transmitter, and data out of the receiver with my digital oscilloscope. They are presented in the following section.

Signal 1 (Transmitter, TTL input logic 0), Signal 2 (Receiver, TTL output pulsing signal)

The yellow line at the top is the signal input to the transmitter module (Signal 1). The blue line below is the signal output from the receiver module (Signal 2). The left scope display is the zoom out view, while the right is the zoom in view.

The transmitter is transmitting a logic 0. The output shows the periodic pulses indicating logic 0 or no transmission detected. This is the reason why the LED indicator keeps blinking. The receiver output is pulsing on and off.

The running pulse width is not consistent, ranging from 20ms to 30ms. The pulse period of 80ms is rather constant when I measure the falling edge.

Signal 1 (Transmitter, TTL input logic 1), Signal 2 (Receiver, TTL output signal pull down to 0.8V)

Now the transmitter is transmitting logic 1. The output signal is now constantly pull to 0.8V (I will consider it as logic 0). The logic 0 output will drive the LED constantly on, which is what we have observed earlier.

Signal 1 (Transmitter, transition from logic 0 to 1), Signal 2 (Receiver, output signal response)

This is how the transition looks like when the transmitter transmits from logic 0 to logic 1.

The response is pretty simple and within my expectation.

Signal 1 (Transmitter, transition from logic 1 to 0), Signal 2 (Receiver, output signal response)

This is how the transition looks like when the transmitter transmits from logic 1 to logic 0.

The response is a bit tricky. The receiver took some time to pulse it’s output periodically. There is a consistent delay between the first pulse and the subsequent pulse. First pulse width is able 50ms, followed by a 150ms delay, before the periodic pulses return.

The pulsing period of 80ms (12.5Hz) is going to cause some issue when decoding the transmitting data. It will be very slow differentiating logic 0 and 1 from the transmitter.

2012-05-19

The setup is further tested. The transmitter and receiver module is now 2m apart using separate power supply.

The experiment fails. The receiver did not response. Even when both circuit is place very near each other (10cm apart), the receiver fails to response. The pulsing signal is more random than the experiment above.

The antenna was then pulled very near the receiver module, the receiver starts to function properly as before.

I have came to read a relating article online. The symptom is very similar to what I have describe. The issue is due to improper tuning of the receiver. The module should works after proper tuning. I may have to verify this for my next experiment.

During my work in Teleradio Engineering, I am task to research in the area of magnetic field. Eventually some ideas were came up with to test out on radiated electromagnetic field. Electromagnetic field is simply the energy form by magnetic and electric field. The theory details on electromagnetic field is very mathematically intensive as what I had go through during my diploma and degree courses. However the concept is actually quite simple. Mathematics is simply one of our human language which can accurately be used to describe the physical property of electromagnetic. The deriving of the mathematics has gone through a lot of work. Eventually electromagnetic can be accurately predicted by the famous Maxwell Equations.

Wow, you may think, four simple equation and they have describe almost over 90% of electrical and magnetic phenomenon. These four equation are headache to study.

Electromagnetic theory is a form of geometry mathematics. If you can understand the concept of volume, area and vector in school, you have the potential to master this subject. It is not as difficult as it seem to be. You will have to apply some imagination and interpret the electromagnetic concept because these thing is physically not visible.

A book that have great influence in my understanding in electromagnetic is “Electromagnetism for Engineers (An Introductory Course) 3rd Edition by by P.Hammond (University of Southampton, Southampton UK)“. This book is fully recommended for beginners like me, as it has minimum mathematics which is very easy to read and understand. Most importantly, the book is thin and have sufficient pictures illustration.

Electromagnetic theory is a very useful in practice. The learning experience is applicable to a lot of engineering problem. I had manage to apply the knowledge to resolve lightings issue during my research work in Teleradio Engineering. It all started when I was confronted with my first commercial system (UV3, Under Vehicle Surveillance System) that I build for the company. A new chassis design were already in place before I join the company. After a test run, it is found to have lighting problem. The lighting positioning is wrong, resulting in dark images captured. We have to resolve this immediately because the delivery date to our oversea buyer is near. I am confronted by a problem which I was not trained to resolve in school. Number of simple reflector were made for testing but it does not seems to work well. I decided calm down and rethink the problem all over again. All our office’s fluorescence lighting were switch off. The bulb is being switched on, as I observed the bulb glow, the radiation pattern of the bulb. Within the next few moment, electromagnetic concept surface in front of my mind. I had come up with a simple custom reflector design base solely on the radiation pattern and managed to resolve the lighting issue for delivery. Although the concept of reflector is quite simple, it took me over a year to be able to understand and explain the lighting’s intensity distribution from all the various reflectors I have designed. I have spent much of my time in Teleradio doing reflector design and lightings research for camera vision.

The illustration of the light radiation from a bulb is very much similar in a way to electromagnetic theory.

LM7805, TO220 package

SD-50A-5

  SDM-30

PMA8811SF

UT70A

Various type of voltage regulator design

a) Zener diode voltage regulator.

Suitable only for very low power application.

For Vcc 24V
– Zener (Vout) = 12V 240mW, Iout(max) = 20mA, Rreg = 600ohm 240mW
– Zener (Vout) = 12V 120mW, Iout(max) = 10mA, Rreg = 1200ohm 120mW
– Zener (Vout) = 5V 100mW, Iout(max) = 20mA, Rreg = 950ohm 380mW

For Vcc 12V
– Zener (Vout) = 5V 100mW, Iout(max) = 20mA, Rreg = 350ohm 140mW
– Zener (Vout) = 3.3V 66mW, Iout(max) = 20mA, Rreg = 435ohm 174mW

Refer to the following website to compute zener, resistor value for a required Vout/Iout.
http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

b) 3 rectifier diodes as voltage regulator.

Suitable only for very low power application.

c) Using voltage reference TL431 as a voltage regulator.

This is a very simple and useful adjustable voltage regulator. If the load is <100mA, this is a very attractive solution. For 5V output, R1=R2=10Kohm. TL431 datasheet.

d) Linear voltage regulator.

Suitable for application that requires low noise.

e) Switching voltage regulator.

Suitable for application that requires high power.

Circuit diagram taken from,

A dc-dc regulator/converter or another name known as buck regulator or switching regulator, provides stable regulated output voltage to supply electronic circuits. Schematic, PCB layout and component list are available on this page.

LM2576 circuits perform same function as the commonly known voltage regulator LM7805 from National Semiconductor. The 7805 voltage regulator dissipates a lot heat. The higher input voltage, the more heat is generated. The extra input energy is converted to heat, keeping the output voltage regulated at 5V.

LM78XX series is available to regulate 5, 6, 8, 9, 12, 15, 18, 24V. If you want the output voltage adjustable, there is also a adj model. For -negative voltage supply, you can use LM79xx series. These regulator is able to support up to a maximum of 1A current rating.

LM7805 IC requires input voltage to be higher than output in order to regulate the output voltage. Input voltage needs to be at least 7V (up to a maximum of 20V) in order for LM7805 to regulate at an output of 5V. It is advisable to supply a voltage input range from 7.5V to 10V. Any higher input voltage is consider inefficiency, generating a lot of  heat.

A switching mode power supply such as LM2576 dc-dc converter, uses switching control to reduce the input dc voltage on average. This is equivalent to a lower input voltage resulting in minimum heat dissipated. The control results in better regulated output, less energy wasted through heat and the use for high current application. Nowadays dc-dc converter are getting smaller and comes in the TO-220 package too. You can simply change your LM7805 to dc-dc converter without any change in your design.

The first commerical module I tried is the SD-50A-5 from Meanwell rated at 5V 10A. It is very good and easy to use. However it is very big and bulky. If size is a constraint, you might consider the model SDM-30. It is able to handle up to 5V 5A and is a lot smaller than SD-50A-5. However it generates a lot of heat through its metal casing.

The best dc-dc I have tried before is PMA8811SF from Ericsson. It is by far the most compact (smaller than SDM-30) and most efficient dc-dc. Heat is also dissipated through it ceramic package, however it does not scalded your finger as much as SDM-30 do.  The IC package is surface mount however soldering is relatively easy because the IC leads are quite broad. It is rated at output 5Vdc 16A and generate far less heat. Each pieces cost about S$60, a lot more than the other converter model.

Through some research, I get to learn about commercial standard dc-dc IC that perform with only a few external components. The following article discuss on LM2576 IC with rating up to 5V 3A. LM2576 is one of the dc-dc IC product range from National Semiconductor. There are also various brand of dc-dc regulator IC available.

The interfacing of most dc-dc IC requires the use of inductor. This is the case for LM2576 too. Try sourcing your local electronics shop for one if possible. I am not stopping you to make your own inductor. Just that making your own inductor takes up time and it is very likely to cost you more than what a shop might be selling.

If you are interested in making your own coil, you might interested in this website, http://www.skylab.org/~chugga/mpegbox/coil/. The aurthor Jeff Mucha had demonstrated a simple and creative way to make inductive. One Long screw, 2 board flat washer, 2 nut, 1 ring spacer, glue, and XXX is all the tools that is require to make your own air core inductor. It is really interesting.

More article: home brew your own inductors

Jens Moller has contributed a program which generate a table of information for building air core inductor. Simply input the inductance value you need, the program will display a table containing the wire coil height radius and number of turns required. You need not have to understand formula to make your own inductor. Take a look at the following website, http://www.colomar.com/Shavano/inductor_info.html

A greenhorn when I first attempt to use inductor. It is a tough job building circuits using inductor. I do not have proper equipment to measure the inductor on hand. Never able to find out the inductance value I have. Fortunately, there is this inductance measurement product selling at an affordable price. UT70A from Uni-Trend Technology. It also function as a multi-meter, and can be used to measure voltage, current, etc… . Even with an inductance meter, it is not a easy task to measure inductance accurately.

Other reference:

The practical basic of building a power supply.

– The Power Supply.pdf

http://www.talkingelectronics.com/

projects/ThePowerSupply/Page79PowerSupplyP1.html

2009-09-13 dc-dc step up, LED driver using 1.5V alkaline battery

The simplest DC-DC step up converter I have done. Typical LED requires about 2V to operate. This ciruict is able to drive the LED from a 1.5V battery. The transistor forms the oscillating circuit generating pulsing output. Although the output is pulsing, we can’t actually see it on the LED, as the switching is quite fast.

Click the picture to enlarge.

The voltage output is about 3Vpeak oscillating at about 33kHz.

Schematic

Photos of DC-DC circuit built

This is the 1st successful DC-DC circuit I built.

There a variety of capacitors out there in the market. Capacitance, voltage rating, dielectric material, etc… . Choose a suitable voltage rating across the capacitor. The circuits deals with high current, therefore it will be better to choose a low ESR (equivalent series resistance) Aluminum electrolytic capacitor. As a general guide, a higher voltage rating has lower ESR rating.

The inductor coil use should be able to handle the current passing through the inductor coil. If the wire is too thin, the coil may be burn or just fail. My previous circuit uses small wattage inductor (package like a big resistor). The circuit couldn’t work and was later found to be IC problem. I have not yet do a test to check on the possibility of the inductor contributing to the failure.

Using a inductor meter to measure the inductance will be easier. Inductance value can be observe immediately for any modification to the coil of wire. The inductance value can also be calculated, depend on the coil size, number of turns, wire size used, dielectric of the core etc… .

The 1N5822 is a high current, high speed, schottky diode and is suitable for this digital switching circuit. Schottky diode (Schottky Barrier Rectifier), means that the forward voltage drop is low. For this application, a low forward voltage diode is necessary.

Schematics

PCB Bottom Layer (PCB trace)

Component Layout (Silkscreen)

Bill of Material (BOM) for LM2576 circuit

Failure, my first prototype circuit to test out the performance of LM2575, LM2576.

Some of the various sizes of inductor tested and seems to be working with LM2576.

Initially I thought that I had use the wrong type of inductor, resulting in the circuit malfunction. Initially I had used a smaller type of inductor (looks like a resistor). Realizing that this circuit drive high current load, I should use a thicker inductor coil. That’s why I modified the circuit with an inductor (enamelled wire, wound around the ferrite core).

Still it doesn’t work. I guess that both IC LM2575, LM2576 must have been damage by my previous attempt. The capacitor used is suspected because the datasheet call for low ESR capacitor. It is very difficult to find these in the local shops, therefore I use a normal capacitor instead.

One day, I visited a shop selling ready made inductors and brought LM2576 at the same time. The circuit was rebuild and it finally works. My deduction at that time was either the inductor or the capacitor is giving me the problem. After further testing, I find out that ordinary capacitor works as well. There is hardly any difference in performance. Various type of inductor were tested (except the resistor like type). All inductor works too, big or small. Quite weird actually, and I couldn’t figure it out the actual problem I had in my previous attempt.

The mystery is resolve finally. One fine day I went back to the shop where I first purchase my LM2576 and brought 2 additional LM2576 for more testing. A new circuit was build and the familiar failure was observed. The output voltage of 5V cannot be sustain and eventually drop when more than 1A of current is draw by the load. The lab power supply display a current loading limit warning. IC becomes very hot. The datasheet specify that LM2576 should be able to supply 3A without any  problem. Both brand new IC are tested to have the same problem.

This is weird, as the same inductor and capacitor previously tested do not result in this same old problem. However the circuit shows the same failure symptom. The next thing that comes to mind, is the IC. The IC LM2576 from the previous working circuit is then transfer over the new circuit board for testing. Everything works fine. It is then clear that the problem comes from the IC itself.

Checking up on the previous IC, I notice that they are from the same manufacturing batch number and believe that they are already damage in some way.

Sample of the 5Ω 50W aluminum house resistor used for testing 1A current performance.

General tester for LM series dc-dc IC chip.

Some of the newly fabricated board built to support other prototype projects. It has been tested to support a RF transceiver operating at 5V without any issue observed.

Home fabricated circuit board

It has been some time since I learn to use LM2576. The circuitry is able to handle a higher current at 3A 5V output. This translate to a higher cost and circuit size, since all component must be able to handle that high power capacity. These component include the LM2576, inductor and the diode. Since most electronics kit requires less than 1A power supply, it is wise learning how to apply a low power dc-dc regulator like LM2575. Cost can be reduce by 50%.

There is one day that I happen to come across this IC LM2575 while searching high and low for LM2576. LM2576 is actually quite difficult to find. There is only 2 shop I know of, but I have rule out one shop because they are selling a faulty batch of LM2576 IC. LM2575 seems very common from shops around and I decided to find out more about this chip. Indeed it is what I have been looking for, a low power regulator. So I purchase the IC and its component to try it out. When I started writing this acticle, only did I realize that I have actually tried it about 6 months ago. The experiment was forgotten after a series of failure.

The following experiment is done during the 1st test on LM2575 circuit. The experiment compare between the performance of using different inductor. One using a wire coil inductor, and the other smaller one inductor that looks like a resistor with it’s color bands..

The photos on the left column shows the LM2575 circuit using the correct inductance value at 330uH but the inductor is low power rated. It is small and looks like a color coded resistor.

A few second after the left circuit is powered up, the small inductor turns very hot. The waveform observed at the output of the dc-dc regulator, contains a high amount of noise/ripple energy.

The photo on the right column shows the same circuit using a slightly higher inductance at 480uH but the coil is thicker and bigger in size.

The circuit using a high power rating inductor on the right shows a cleaner DC supply, although the inductance value is different from the design. There is still ripple at it’s output but I guess it will be minimum using an inductance value of 330uH with higher power rating. Too bad, I do not have the right inductor to experiment further. It is either coil one myself or buy one from shop.

12 June 2006, Lim Siong Boon

I have found this article regarding about the property of inductor Isat (current saturation) and Irms (continuous current). They are usually one of the important specification to take note while selecting inductor from datasheet.

Current saturation means the amount of current required that flow through the inductor, in order to reduce the inductance of the component.

Continuous current means the amount of current required to heat up the inductor to a certain temperature. If the amount current continue to flow through the inductor, the inductor is basically becoming a heater. The temperature depends on the amount of current flowing through it.

The following contains information that I learn from.

Isat_Irms explain.pdf

02 Dec 2008, Lim Siong Boon

LM2575 Schematic taken from National Semiconductor LM2575 datasheet

Bill of Material (BOM) for LM2575 circuit

I happen to see this very good website, teaching about handling noise. There are many illustration which are easy to understand.

http://www.williamson-labs.com/480_byp.htm

04 Oct 2011, Lim Siong Boon

Switching Power IC

LM2575, LM2576, LM2596, LM2678

The following table provides a quick reference for power supply circuit. The circuit schematic and component list are selected from the manufacturer’s datasheet.

For exact component value design, you need to the datasheet. The following component value is design for typical input voltage of 12Vdc or 24Vdc drawing power at 75% of the current rating.

LM2575 (1A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

– LM2575-3.3 (3.3Vdc output)

– LM2575-5.0 (5Vdc output)

– LM2575-12 (12Vdc output)

– LM2575-15 (15Vdc output)

– LM2575-ADJ (1.23Vdc to 37Vdc output)

Alternative:

NJM2367

Package: TO-220(T)

LM2575 datasheet

Click for LM2575-adj circuit

Component list