S3: Add hardware verification tests/scripts

[adamkewley]

Some teams encountered hardware issues in S3 during yesterday's session.

Issue list:

• HX711 module not found (1 case yesterday):

  • Library was somehow mis-installed during kit prep
  • Fix it by getting the latest pbl support code (guide in README: https://github.com/PortableBalanceLab/PBL/tree/main/X0_SoftwareSetup/pbl), followed by reinstalling the software with sudo pbl install s3
  • Test it's fixed with pbl test, or by re-running the faulty script
  • The test suite was updated to ensure future kit preps can better identify mis-installed software (via pbl test), which is why the pbl support code needs to be updated on 2023's Pis

• Mis-wiring the jumper cables (1/2 cases yesterday - this should be checked first):

  • Manifests as "cannot zero ADCs" or similar
  • Source: usually, because the Pi was wired upside down.
  • It would be handy for the python code's error message to communicate that possibility
  • Or, at worst, for the lab notes to mention "be careful which way up your Pi is"

• Faulty load cell amplifiers (3 cases yesterday):

  • Manifests as "cannot zero A_PARTICULAR_PIN", or similar, where A_PARTICULAR_PIN on the Pi will be connected to a faulty load cell amplifier on the PCB.
  • Students will manifest the bug when initially running calibrate.py Clk Pin1 Pin2... etc.. The script requires that all load cell amplifiers connected to PinXs are operational.
  • The bug can be verified by re-running calibrate.py without the faulty pin. The script should then run fine, but be missing the faulty device's information - this indicates that it is a hardware bug with one specific load cell amplifier.
  • The bug can be fixed by physically removing the faulty load cell amplifier (red PCB) the motherboard (green PCB) and replacing it with a new one.
  • If the fix doesn't work, reset the Pi and try running calibrate.py again
  • If the fix still doesn't work, it's a different problem.
  • The bug is a hardware QA issue.
  • The long-term solution is to write automated QA code that tests each load cell - ideally, this should be ran on each kit before distribution