value, rc = mc.mcAnalogInputRead(inst: number, analogInputNum: number)
value, rc = mc.mcAnalogOutputRead(inst: number, analogOutputNum: number)
rc = mc.mcAnalogOutputWrite(inst: number, analogOutputNum: number, value: number)
They don't look like they're in the API docs yet, but if you're in ZeroBrane they should come up as suggestions.
I've never used them, though I think analogInputNum and analogOutputNum is just the number of the input or output? So to read "Analog Input 1" it'd be mc.mcAnalogInputRead(inst, 1), given you have that assigned to something in Mach4's Config.