I finally found a “fix” for the fact that my ESP32 devkit kept dropping WiFi when not powered by USB. I searched all over for this and found a bunch of answers, but thought I’d post my symptoms and fix in case it would help anyone or spark anyone’s interest.
Issue: ESP32-WRoom 38 pin dev kit module would rarely show up on WiFi unless powered through the on-board USB port (5V application to 5Vin pin and ground wouldn’t work). The power LED on the board would light up, but the module could not be seen on WiFi unless powered directly through the USB port.
Fix (I don’t know why this works): I have to have GPIO 2 as one of the LED output ports. It doesn’t matter which LED output is set to GPIO 2, but at least one has to be. When I do this, the blue LED on the dev kit will illuminate with activity and the WiFi connection is solid. This issue only seems to exist on these Teyleten Amazon dev kits I bought. I have several quinLED boards and I don’t have to do this with those.
I went through a whole dirty power, old flash, bad board multi-day troubleshooting effort, but the GPIO2 setting was the final fix. Just something to try in case others are having the same issue. I don’t have GPIO2 in any of my PCB designs, so I just made GPIO2 a last,superfluous LED output and gave it 1 LED.
Environment: esp32 v3.2.3-14-gd3e562907
Board: ESP32S ESP-WROOM-32 Development Board (by Teleten - bought on Amazon)
The real issue is wonky shottky diode on the ESP board. Unsolder it and bridge contacts with a piece of wires.
Make sure you do not power the ESP with USB and external PSU at the same time.
Thanks, it was working but if I unplugged it it was a hit or miss if it came on. Now it chooses not to come on unless I am using a USB power source. attached is the board, thx.
Simple test as noted in that article, power on 5V only and press EN button to force a reset.
If the board boots up properly, you very likely need a reset capacitor.
I’ve had to mod a few of those series boards myself, but mainly to deal with the flashing issue.
I use a 10uF cap from EN to Gnd and it solved the problem.
Thanks to all the conversation here I figured out how to solve this problem. At least one of my ESP32 boards exhibits this exact problem. While connected to the USB port on my laptop it works great (4.9v), but when I plug it into the 5v wall transformer (5.2v) it fails to boot. That was incredibly frustrating. I cut the plug off a USB cable and wired the cable to the board via a Development Board. It’s ugly and should be unecessary, but it solved the problem. Now this ESP32 boots and connects to wifi. There is definitely an issue with voltage above 5 volts that prohibits the device from booting properly while being powered by the microusb port.
