//DIGITAL_READ(2, A4, 4); //Not avaliable on Arduino Uno, i2c pin. //DIGITAL_READ(2, A5, 8); //Not avaliable on Arduino Uno, i2c pin.

I2Cwrapper is a firmware framework which helps you implement Arduino based I2C target (slave) devices for control of non-I2C hardware. Supports plain Arduinos, ESP8266, ESP32, SAMD, STM32, and ATtiny ...