Raspberry Pi - Revision 2 DIY Add-On Board

On the Raspberry Pi, there are several connections which can be used for expansion:

    1, The Rpi GPIO (General Purpose Input/Output) pins are exposed, that means that expansion
          boards are able to talk directly to the CPU.

     2, The DSI connector will allow low-level interfacing with LCDs and other displays.

     3, The CSI connector will allow camera modules to be added in future.

Step 1: Raspberry Pi Single Side DIY Add-on PCB With 5V/3A Buck Regulator Power Supply.

Raspberry Pi - Revision 2 DIY Add-On Board

Features:

5V/3A power-supply
buffered interface to GPIO pins
4 button switch
3 LED [include 1 hardware PWM] - external connectors also available
1 Relay
5V logic Level UART interface
16x2 LCD [74hc595 based] with back light control option
SPI ADC MCP3008
DS1307 with battery backup holder
24C032 EEPROM
PCF8591 DAC_ADC
i2c external connector [3.3v to 5V logic converter included]

Step 2: Block Diagram of Add-on Board

block diagram representation

LM2587 Buck regulator : 5V/3A power supply

3.3v to 5v level shifter : ic74HCT125   -single direction

3.3v to 5v level shifter for i2c : MOSFET 2N7000 based    -bi directional

24c032 :eeprom

battery: 3V RTC backup battery

DS1307 : i2c based RTC chip

PCF8591: i2c based ADC-DAC chip

4 switch: user input button switches

MCP3008: SPI based 10-bit Analog-to-Digital Converter

74HC595: 3 wire serial LCD interface

16X2 LCD:    16 character x 2 line monochrome LCD [serial interface -74hc595]

LED 1-3 : LED output 3 color LED [include h/w PWM pin ]

RELAY:   for heavy   load application

Step 3: Raspberry Pi Revision 2 26 Pin Gpio

note:

Raspberry Pi single side DIY add-on PCB with 5V/3A buck regulator power supply board designed for Raspberry Pi Revision 2

Step 4: Circuit

circuit diagram list

gpio relay led connection circuit diagram
gpio button switch interface circuit diagram
add-on board and raspberry pi powersupply circuit diagram
i2c interface circuit with ds1307 RTC and EEPROM circuit diagram
LCD and MCP 3008 interface diagram.

Step 5: PCB

PCB layout : single side glass epoxy PCB
schematic and PCB tool : proteus 7.10 [3d view support]
hand soldering

Step 6: Raspberry Pi With Add-on Board

add-on board with raspberry pi - photos

Step 7: Experiments

i2c device listing output

commands for i2c device listing
http://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

1, sudo nano /etc/modules

2, and add these two lines to the end of the file:
i2c-bcm2708
i2c-dev

3, sudo apt-get install i2c-tools

4, sudo nano /etc/modprobe.d/raspi-blacklist.conf

If you do not have this file then there is nothing to do, however, if you do have this file, you need to edit it and comment out the lines below:

blacklist spi-bcm2708
blacklist i2c-bcm2708

.. by putting a # in front of them.

5, sudo i2cdetect -y 1