Hi, just to clarify:
For the two chips that start up normally and work for about 3 minutes before becoming unresponsive to SPI:
- I removed power from the board and checked for shorts using a 9V multimeter.
- Once I confirmed there was no short, I powered the board again. The circuit then worked for the aforementioned 3 to 5 minutes before becoming unresponsive once more.
So, it doesn’t seem like the multimeter voltage is damaging the chip.
I have since discovered that the flux I used — Pro’sKit 8S005 — wasn’t thoroughly cleaned off. Since this flux is slightly conductive, it most likely caused the issue. For the chips that were starting up properly, I removed the remaining flux by heating it and then cleaning the chip and PCB with ethanol. After this cleaning process, the issue appears to be resolved.
As for the other chips that are permanently shorted between VCC and GND, it seems there’s nothing I can do to recover them.
The design was based on the ESP32 UWB DW3000 module by Makerfabs, and I believe the RESET pin was configured for open-drain operation. I also verified that all GPIO pins are operating at 3.3V, and that VCC is consistently 3.3V as well.
Thanks again for the feedback!