Photon Output Voltage Level

Does anyone know where I can find the documentation that will show all of the voltage logic levels for the photon? I do not see it on the datasheet; I assumed that information would be here: https://docs.particle.io/datasheets/photon-datasheet/#recommended-operating-conditions

I’m mostly just looking for the maximum voltage level when a pin is set to HIGH (Voh) and whether or not that changes if your powered off of 5V from a USB cable or from something at a lower voltage like a 3.7V Lipo.