Communication Protocols

Reference notes for common peripheral buses used in Arduino, ESP32, Pixhawk, and robot sensor wiring.

In this section

• Serial — non-blocking UART receive, markers, and parsing (Robin2 tutorial)
• UART — hardware serial ports, wiring, baud, and Serial vs USB
• I2C — two-wire bus, addresses, Wire, register read/write
• SPI — clocked bus, CS lines, modes, and SPI.transfer

Quick comparison

Protocol	Typical wires	Multi-device	Arduino API	Common on robots
UART (async serial)	TX, RX, GND	Point-to-point	Serial, Serial1	GPS, telemetry radio, debug
I2C	SDA, SCL, GND	Yes (addresses)	Wire	IMU, magnetometer, OLED
SPI	SCK, MOSI, MISO, CS, GND	Yes (per-chip CS)	SPI	SD card, LoRa, CAN controller

For message framing and parsing on UART, start with Serial. For pin maps on ESP32, see ESP32.