I was fairly close to being ready to declare this printer running at an alpha state and add it to the Marlin 2.0 compatibility table. All I had to do was get a few test prints done and I'd be happy.
First, I found an issue with my variant in Arduino. In ST's core, every pin has to be mapped to an ADC if it's going to be used for analogRead(). And guess who didn't have an ADC for the hotend pin.
I wire everything up...and still don't get a reading. This sent me down a rabbit hole checking and rechecking, but finally I hit an easier answer. We're at the part of the project where theory meets reality, and the bits and wires intersect.
I had a broken thermistor. I don't know where it's broken, but it is. So I wired in a new one...and discovered my hotend was destroyed. How did this happen?
One of the last fixes I did fixed the E0_AUTO_FAN, so the hotend is automatically cooled. But right before that, I'd done a temperature test, and (sigh) cooked the PFTE liner in my hotend.
Good news? Thermal runaway detection at both min-temp and max temp works 100%.
Bad news? I'm wiring a new hotend into the printer.
At that point, I'll print the lucky cat...and have a beer.]