PSU Tester

With the power supply problem I had with Pod, I kinda wanted to make my own PSU tester (I sah "Bah!" to the ones I can buy), and I just took some notes down and kinda forgot about it. I decided to use the ATSAMD21E18A-A because it has six analogue input pins, which is more than enough, and I had to figure out the resistor values for the the voltage dividers that would bring 5 and 12 volts down to 1.65 (half of 3.3 volts). I had also gathered some parts that I would need for it and shoved them into my notes, and I also have notes to have a switch to be able to change the 12-volt rail to be checked. I thought to use the leftover NeoPixel Nano 2020 LEDs for indication, but later I thought that an LCD or OLED screen would be a little better.

I also looked up how to measure negative voltages, and wasn't surprised when I found the answer was op-amps. I also found out that the pwr_ok signal is actually a timed thing and the voltage on it should come on no sooner than 100ms, so I added that piece of info to my notes. I really don't have a lot done with this project since it actually was started after the MCU/CircuitPython project "craze", and I didn't feel like working on the board much past plopping some of the planned items down. I have notes that I might need a crystal, but I also have no idea where the power for the MCU is going to come from. Ideally, I'd like to keep it separate from the power supply, but it's another decision to make before working on the project more. I probably will just add the crystal and its capacitors in anyway, but we'll see.