Use interrupts to read HC-SRO4 distance sensors without delays or blocking the main loop.

Tested on the Alfredo Systems NoU3

wiring:

The HC-SRO4 needs to be powered by 5 volts not 3.3v (so use the regulated 5 volt servo power).

The ESP32-S3 in the NoU3 can only provide 3.3 volt outputs and can only survive 3.3 volt inputs.

A 3.3 volt signal is enough to trigger the HC-SRO4, but the HC-SRO4 will output a 5 volt echo signal which would be bad for the NoU3 if connected directly.

Two resistors can be used to divide the echo signal to a safe voltage for the NoU3. echo -- resistor -- NoU3 pin -- resistor -- ground

The resistors should be approximately equal and can be most values (1k -100k ish). I used two 1k resistors.