GPIO0 pin driving low at boot resulting in boot failure
Posted: Thu Feb 24, 2022 5:42 amGood morning,
I have a very odd behaviour I'd like to get clarification on:
- custom PCB using an ESP12F, which was working fine before, suddenly stopped working
- after multiple investigations (reflashing using FTD32, etc), I realized that GPIO0 pin reading was at 1.9V (GPIO2 was at 3.3V)
- Schematics are super simple: these two inputs are pulled-up to 3.3V. When measuring on PSU side of the resistor I see a nice 3.3V, when measuring at ESP side of the resistor, 1.9V
That would explain why the ESP does not boot, since I assume it's entering flash mode (1.9V is just below TTL level)
But now... why in the world would the ESP input try to drive this signal low ? I can only think of a defective input, but that seems a stretch (ESD damage maybe ? I was indeed manipulating the board at one point, but did not mishandled it though)
I have a very odd behaviour I'd like to get clarification on:
- custom PCB using an ESP12F, which was working fine before, suddenly stopped working
- after multiple investigations (reflashing using FTD32, etc), I realized that GPIO0 pin reading was at 1.9V (GPIO2 was at 3.3V)
- Schematics are super simple: these two inputs are pulled-up to 3.3V. When measuring on PSU side of the resistor I see a nice 3.3V, when measuring at ESP side of the resistor, 1.9V
That would explain why the ESP does not boot, since I assume it's entering flash mode (1.9V is just below TTL level)
But now... why in the world would the ESP input try to drive this signal low ? I can only think of a defective input, but that seems a stretch (ESD damage maybe ? I was indeed manipulating the board at one point, but did not mishandled it though)