GoForSmoke:
Do the analogRead in the IRQ?
No, I didn't write that. If you can fiddle with timer interrupts, you can pick apart analogRead, and use that knowledge to set the input mux and start the conversion.
Or "initiate/start" it there and catch the result later?
Can that be done? I thought we want other activities quiet during ADC. I must have this wrong.
Quiet? As in the busy wait inside analogRead, with the processor running full pelt? What's the difference?