I2C communication out of sync, ESP32

[jim-p]

For the ESP32 you need to use slaveWrite. It is used in the onReceive function not the onRequest
See post #7 in this topic

Understanding ESP32 WireSlave example

I've been picking apart the WireSlave example from Espressif ESP32, I seem to mostly understand how the communication between the Slave and Master works. Original example code: https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/examples/WireMaster/WireMaster.ino#L23 https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/examples/WireSlave/WireSlave.ino#L28 However, the pre-processor code (see below) within setup confuses me. As it seems to work like a macro …