Many development boards for sensors and microcontrollers have adopted the Arduino Uno R3 header configuration. There are plenty of derivatives to this but some commonality does exist. When designing a Shield whether it be for a MCU (target) or a sensor/radio/peripheral (device) using the following guidelines will ensure the most cross-target and cross-device compatibility.

Wiring Diagram¶

Peripheral Mapping¶

All labeled from the targets perspective

Target Implementation¶

• Avoid wiring a single MCU pin to multiple breakout headers
• SDK should resolve names to MCU specific pins (PinNames.h)
  • A0 ... A5
  • D0 ... D15
  • I2C_SCL ... I2C_SDA
• Order of prescience for IO is 0 ... 13 (analog and digital). If not enough pins are available, connect starting at 0
• Female headers installed on topside of PCB
• All digital pins should be gpio interrupt capable (InterruptIn implementation)

Component Implementation¶

• Serial TX and RX need to be swapped
• SPI MISO and MOSI need to be swapped
• Provide a well documented C++ library for all on board components
• Provide a well documented demo application that uses the provided libraries in a simple but meaningful way
• Test you design on as many platforms as possible and document known incompatibilities. These should be the minority and easier to maintain
• Pass through male to female headers should be installed on PCB. Example
• Silk screen on the PCB should clearly indicate if a pins is consumed by the shield or is shareable with other components