Single Channel Incoder

I am searching for the easiest way to modify the firmware of the Odrive such that it supports a single channel encoder.

From what I can tell, it seems that the Odrive keeps track of the encoder pulses using a hardware timer counter. It expects two channels providing a signal in quadrature, and for every set of pulses, one from each channel the counter, increments by four. If there is only one channel providing pulses, the the counter increments and decrements by one repeatedly. It also seems that this is implemented in hardware and there is not way to change how the pulses increment the counter in software. Is this correct?

Correct.

What encoder do you have that only provides a single output?