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
- 16×2 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.
For more detail: Raspberry Pi – Revision 2 DIY Add-On Board