Sonar for APMRover

How/where do I connect a sonar sensor?

I thought about that too. To one of the ADC channels, is my guess.

I believe that this method should work right away, but it should be tested. We also have a couple spare channels on ADC but on Navio+ we had to move them to pads under the board and they are not very convenient to use. I2C is a better option.