

Perhaps I will do that.
But I guess it’s worth mentioning that I have some bad house wiring. I switched off a light to work on it and got shocked (yeah, in principle for safety I should also turn off the breaker but still this should not happen). When lights are off at night, some LED lights are still very faintly lit. When I was messing with serial port wiring I think I touched the 5v and 0v… perhaps each with a different hand, and felt a shock. 5v should not shock me but I think my ground connections are maybe dodgy. There is proper ground pipes in the basement but maybe someone wired neutral to ground or something somewhere in the house.
I would like to have a scope or logic analyser. Someone told me a logic analyser would be sufficient for this… and also sufficiently cheap.
I have an Arduino clone but the EEPROM is apparently embedded in the MCU.