The PCB must be mounted floated, otherwise key presses don't work reliable. Connect pins 3 and 4 on connector P1 for 16-pin button mode. Smaller keypads with less pins may work, but are not tested.

C++ 20 contains the core language support needed to make coroutines (async/await) possible, but it does not provide the related types needed to write an actual coroutine or functions to consume ...