Help needed - New ESP32 PICO D4.1 design continously looping with RTCWDT_RTC_RESET

[deandob]

The new board looks to be OK, the problem was the peripheral connection.

Lesson here - even though the PICO is a module on chip it still needs careful attention to PCB layout and decoupling.

Thanks for the help.

[mark.jeronimus]

Another solution

A coworker had the same exact symptoms as OP on his custom PCB, but he ruled out power instabilities. We conveniently have multiple PCBs, and they all behaved exactly the same. It turned out nothing more than a missing route.

The 3V3 rail entered the PICO on pin 46 (VDDA) but not pin 43 (VDDA). Even though the pins are labeled identically, they're apparently not connected internally. When powered, pin 43 measured 0V. After adding a patch wire between pins 43 and 46 (not caring about the "NC" pins in between), the PICOs all started working like a charm!

[ESP_Sprite]

Note that in general, if a chip has multiple power pins, unless you have a very very VERY good reason not to, you want to hook all of them up on your PCB even if they all seem to be inter-connected internally. There may be other factors at work (current-carrying capacity of bond wires, impedance to large power-using parts in various regions of the silicon die, multiple-die solutions requiring multiple power connections etc) that require power on all pins.