After a quick discussion with Trent over the phone, here’s an attached file that outlines the issue we discussed and the background information that might help to troubleshoot it.
I’d be very, very, grateful if you could take a look and provide some advice as to what might be causing this issue and how I can recover my bricked MKR Zero and any future boards that I manage to brick as well.
For anyone following along, there are instructions that have been followed to attempt to reflash the bootloader on the bricked boards using these pins: SWDCLCK, SWDIO, SWDRESET, VCC and GND listed here that worked on 2/3 bricked boards:
I’d like to learn more about what could be causing the issue. Out of curiosity, are you still getting 3.3V and 5V stable on those rails on your last remaining still bricked MKR? I’d be keen to see whether on the 3V3 and +5V pins against GND whether the voltage is the right level and stable. A response of zero rather than seven when attempting to write the register seems suspiciously similar to the behaviour when below operating voltage.