Some usesful sketches for Arduino-compatible microcontrollers:

• I2CScanner scans I^2C addresses

• SPIPins reports pin numbers for the SPI bus

• DigialPinProbe writes a brief square wave to a specified digital pin for checkin with an oscilloscope

• Esp32MacAddr reports the MAC address of an ESP32 board

• EspNowReceiver writes incoming ESP-NOW bytes to serial output