WIRING of KY-040 Rotary Encoder plus Demo Code

Other Hardware General Electronics
36

I have a low-bandwidth application (digital lock for an escape game). In my case I only need digits 0..9, so coded the interrupt like this:

void isr() 
{
  if (digitalRead(ENC_A) ^ digitalRead(ENC_B)) {
    if (encValue < 9)
      ++encValue;
    else
      encValue = 0;
  }
  else {
    if (encValue > 0)
      --encValue;
    else
      encValue = 9;
  }   
}

Note that the interrupt is triggered on a state change of the ENC_A pin. There are some who recommend against polling inside the interrupt, but in this case I think it's a good idea as I can determine direction using the current state of the encoder pins and update the encoder value so that it is available to any part of the application.