Tip and Ring on the OWL Pedal go to two pins on the microcontroller called PA2 and PA3 (port A pins 2 and 3), via a pair of resistors. Sleeve is permanently connected to ground.
PA2 and PA3 are configured as one fixed 3.3v output, and one ADC (analogue to digital) input. So the output pin provides a voltage which the the expression pedal divides down to a lower voltage for the ADC to read.
The pins could equally well be configured as digital inputs with internal pull-up resistors enabled. This would mean that when not connected, they will give a high / on value thanks to the pull-ups. When either is shorted to ground/sleeve by a switch, they will read low / off. If we invert the values we get two switches.
tl;dr: yes! but the firmware doesn't support it (yet)
This might be a common enough use case that we should build it into the firmware as a configurable option.
I've opened an issue: https://github.com/pingdynasty/OwlWare/issues/25
Question is: what parameters or buttons will the two switches be mapped to in the patch? One can set parameter E to either 0 or 1, but what about the other switch?