Add-ons
Every add-on connector is keyed to one host. Pi 40-pin HATs, Arduino shields, and Adafruit FeatherWings are not interchangeable — the same motor driver or display will often exist in all three formats, sold as different products.
About 270 add-ons across Pi HATs, Arduino shields, and FeatherWings. The same function — motor control, PoE, display — usually ships once per host connector family. Get the host board right first.
- Raspberry Pi 40-pin HATs cover the full range: Sense HAT (B)/(C) sensor boards, PoE+ HAT, the AI HAT+ 2 with its Hailo-10H accelerator, and PCIe-FFC HATs for NVMe M.2 SSDs that fit Pi 5 only.
- Arduino shields stack on the 5V Uno/Mega headers: Gravity IO Expansion Shield V7.1, Mega IO Expansion Shield, the 2×2A DC Motor Shield, and SparkFun's ESP8266 WiFi Shield.
- FeatherWings (CAN Bus MCP2515, Power Relay, 128×64 OLED, Music Maker, RFM95W LoRa) fit Adafruit Feathers; Bonnets (RGB Matrix, 16-channel PWM/Servo) are half-size boards for the Pi Zero footprint.
- Motor drive is a useful example of the pattern: the same function ships as Waveshare's I2C Motor Driver HAT, a DFRobot Arduino shield, and an Adafruit DC & Stepper Motor Bonnet — mechanically and electrically incompatible, same job.
