A Raspberry Pi-compatible PCB that extends the GPIO header with protected I/O, relays, and various features for versatile use in prototyping and project development.

Notes:

Name

• Pi-multipurpose-Adapter

• Pi-multi-function-adapter

• Pi-extension-board

• universal-Pi-interface-board

• pi-peripheral-interface

• raspberry-extension-board

• Pi-protected-connection-hub

RPI Specs (Zero, 3+)

• Available (old) Pi: Raspberry Pi 2 Modell B v1.1

• GPIO

  • Low: 0.9V
  • High: 1.6V
  • Input current: 5uA
  • Input capacitance: 5pF
  • Output Current +-17mA
  • Pullup / Pulldown 50-65k

• EEPROM GPIO0 GPIO1, leave unused

Feature Ideas

Supply

• Input protection

  • TVS
  • reverse polarity
  • Fuse
  • buffer

• Pass through power supply

• 3.3V, 5V, 12V, 24V Regulator

• power by barrel connector (24V 3A)

• power by usb

  • Switch between power by USB or power supply?

• power by battery

  • liion cell connector
  • BMS / charge controller
  • measure battery voltage
  • USB charging port

IO

• Input

  • GPIO
    • voltage protection
      • 330R, Z
    • wide voltage range 1.6-24V
    • Low pass filter
    • Optocoupler input
  • ADC
    • external IC
    • multiplexer?
    • protection
    • scale input voltage
      • fixed inputs: 24V 12V 5V 3.3V ?
      • trim potentiometer?

• Output

  • Relay
  • Mosfet
  • Optocoupler output
  • GPIO with over current protection
  • GPIO level shift (24V output)
  • PWM pins
  • shift register
  • DAC

• LEDS indicate I/O state

• Testpoints

• ESD protection

Bus

• UART/RS485
• RS232 Connector
• I2C Pullup
• SPI
• CAN
• Serial to usb (if Arduino)
• OWB default GPIO4

UI

• Input
  • Buttons
  • DIP switches?
  • Temperature sensor
  • Encoder
  • Potentiometer
• Output
  • Display
  • Buzzer
  • LEDS

Mechanical

• Barrel plug (24V 3A supply)
• Screw terminals / spring loaded?
• pin header angled?
• pin header for extension
• pass through all pins?

Housing

• RPI ports
• banana sockets for power out
• screw terminal exposed
• buttons, leds: need to open up?
• BNC? []

Other

• Extension board with multiplexer
• Breadboard compatible?
• SD Card
• Onboard MCU for standalone use?
• separate bought MCU via i2c for additional GPIO, DAC, ADC in one

Questions

• what analog input ranges (Voltage, Count)
• RS232 RS485 SPI, IIC actually necessary? examples