Arduino
Uno, Mega, MKR, GIGA, Portenta — and a long tail of compatible boards that share the footprint but not always the voltage. The 5V/3.3V split between the classic and MKR lines bites people more than any other gotcha here.
About 75 boards across every Arduino generation: 5V Uno/Mega/GIGA, 3.3V MKR and Portenta, plus DFRduino and Bluno compatibles. Confirm the voltage rail before stacking any shield.
- Arduino Uno Rev3, UNO R4 Minima/WiFi (32-bit Renesas core), and the UNO Q (2GB or 4GB LPDDR4, 16–32GB eMMC, Linux SoC) all share the same shield headers — very different silicon under an identical footprint.
- The MKR family (MKR WiFi 1010, MKR WAN 1300, MKR GSM 1400, MKR ZERO) is 3.3V with a narrower connector pitch — 5V Uno or Mega shields will not fit and can damage the I/O if forced.
- Arduino Mega 2560 Rev3, Due, dual-core GIGA R1 WiFi and the Portenta line (H7, H7 Lite, X8) cover raw I/O count and clock speed; the Portenta X8 adds a Linux SoC for containerized industrial workloads.
- Compatibles are roughly a third of the group: DFRduino UNO R3 and Nano clones, Bluno boards that splice BLE 4.0 into the Uno/Mega/Nano footprint, and the Arduino Nano ESP32, which blurs the line with the ESP32 family.
