07/30/19 - Proper ESP32 boot without USB connection

A project log for My attempt at an ESP-NOW Mesh

Designing a custom mesh for sensors, home automation and remote controlling using Espressif's ESP-NOW

david-mDavid M. 08/01/2019 at 18:260 Comments

A while back I have encountered a problem with my ESP32 programming fixture. It was resetting the ESP32 if powered with a power supply, however it was fine when powered through a USB plug. To this day, I still haven't figured out what the problem is but here are the steps I took to fully fix the problem:

I'm not sure why pulling pin 12 low helps, but according to this reference guide, it definitely shouldn't be pulled high on boot:

When I saw that bit of information I decided to try it out. I pulled pin 12 low and it appeared to help.

I checked pin 12 with a logic analyzer but it did not appear that pin 12 was being pulled high on boot by the fixture.

Further testing showed that if the power input wasn't sufficient, then the ESP32 could still be booted if pin 12 is pulled high first, then low, which allows it to function for a few seconds before it starts requiring more power for WiFi transmission.