Board Extension Socket/Header Standards

List of possible standards to follow, towards a more extensible board design.

Raspberry Pi

• Raspberry Pi Pinout
• Raspberry Pi HATs, pHATs & Add-ons
• A whole bunch of standard serial interfaces and GPIOs — suitable for powerful boards.

96Boards (by Linaro)

• 96Boards Pinout
• 96Boards add-on boards
• Unless otherwise indicated the connector signals are at 1.8 V logic levels.

BeagleBone Black

• Beagleboard:Cape Expansion Headers – eLinux.org
• BeagleBoard.org Capes – BeagleBoard.org
• Falls short in popularity.

Arduino Uno R3

• Pinout of Arduino Board and ATMega328PU – Wikimedia Commons
• Arduino Shields – Adafruit
• Arduino Shields – Sparkfun
• Uno and its AVR-based variants operate at 5 V; ARM-based variants operate at 3.3 V. We should watch out for potential signal level mismatch issues.
• Contains analog pins, usually suitable for microcontroller boards.

Arduino MKR

• Arduino MKR1000 Wi-Fi Board Pinout – Components101
• MKR Family – Arduino
• Contains analog pins, usually suitable for microcontroller boards.

Feather (by Adafruit)

• Feather – Adafruit
• Introducing Adafruit Feather – Adafruit
• Contains analog pins, usually suitable for microcontroller boards.

XBee (by Digi)

• Digi XBee3 RF Module Hardware Reference Manual – Digi
  • Pin signals for the XBee3 through-hole module
• Products Tagged “Digi XBee” – Digi
• The World of Digi XBee – Digi-Key
• XBee – Adafruit
• XBee – SparkFun
• Single power supply pin, VCC, usually connects to 3.3 V.
• 2.0 mm pitch, not friendly for breadboard prototyping.
• Existing add-on boards are kind of limited to wireless modules.

mikroBUS (by MikroElektronika)

• mikroBUS™ – MikroElektronika
  • Created by MikroElektronika, mikroBUS™ is an open standard — anyone can implement mikroBUS™ in their hardware design, as long as the requirements set by this document are being met.
  • Production-grade standard clarity and design files.
• Click Boards – MikroElektronika
  • Wide variety of add-on boards.
  • Mostly come with schematic.
  • Connects to Raspberry Pi through Pi 3 Click Shield.
  • Connects to Arduino Uno through Arduino Uno Click Shield.
  • Connects to Arduino Mega through Arduino Mega Click Shield.
  • There are Shuttle click and mikroBUS Shuttle when the space is tight.
• Dual power supply pin, 5 V and 3.3 V.
• Adopted by various vendors.
• Looks GREAT for primarily digital, lightweight designs.

Pmod (by Digilent)

• Pmod™ – Digilent
• Maximum of one standard serial interface in each connector — suitable for FPGA boards whose pin functions are easily configurable, don’t have to worry about pinmux.

Grove (by Seeed)

• Grove System – Seeed
• Maximum of one standard serial interface in each connector.
• Uses 4-pin connector, it could contain UART, I²C, but not SPI.
• 2.0 mm pitch, non-JST connector, not friendly for breadboard prototyping.

STEMMA (by Adafruit)

• STEMMA / STEMMA QT Comparison – Adafruit
• Uses 3/4-pin, 2.0 mm pitch, JST PH-series connector.
• Attempts to be as cross-compatible as possible with both Grove and (DFRobot) Gravity.
• Modules are mostly breadboard-friendly, but lack of unified form factor.

Qwiic (by SparkFun)

• Qwiic Connect System – SparkFun
• Specifically designed for I²C.
• Uses 4-pin, 1.0 mm pitch, JST SH-series connector.
• Modules are mostly breadboard-friendly, but lack of unified form factor.

STEMMA QT (by Adafruit)

• STEMMA / STEMMA QT Comparison – Adafruit
• Uses 4-pin, 1.0 mm pitch, JST SH-series connector.
• Cross-compatible with Qwiic.
• Modules are mostly breadboard-friendly, but lack of unified form factor.