How to set up a command-based communication using I2C

[DrDiettrich]

@domi1

I have a hard time understanding how an API call can be undefined. A callback/handler is a function call based on an interrupt;

...or some other event. After the callback function returns the caller can do everything, e.g. flush remaining bytes in the input buffer.

@domi1

if you follow the API calls, you will eventually find out that any read operation on the I2C bus is blocking..

I don't think so. Wire.available() can work as documented only with an input buffer.

@domi1

Since the nRF is a 32-Bit CPU, I defined my struct to fit within 32 bits,

On a 32 bit machine all multi-byte variables should be aligned to their natural boundaries. It will cost some time to access a long variable not aligned to a 32 bit boundary. Also packing a 32 bit byte type into 24 bits is at least questionable. Did you check the struct size and compiler warnings?