ESP32-C3 WiFi signal issue

In one of my projects, I decided to use a board that was new to me - the ESP32-C3. Previously, I had used the standard dual-core ESP32s, but I needed something compact, and the C3 Supermini was a perfect fit.

I took a new module and immediately soldered it onto a breadboard. Then I started porting my code—some issues came up, but fixing them didn’t take much time.

And only after all this, I noticed a significant issue: the Wi-Fi access point (AP) wouldn’t start. The code executed without any errors, but no device could see the network from the ESP Supermini.

 


“Okay,” I thought, “maybe the module is damaged.” I took a new one out of the package - and it worked as expected.

 


Well, I figured I must have killed the first module with static electricity or overheated it while soldering. I desoldered it from the breadboard and, just in case, powered it on one more time. And surprisingly, it also worked! Just like the new one.

 


I investigated various factors that could have caused the issue and found the reason: if anything is connected to pin 21 (GPIO21), the Wi-Fi access point either fails to start at all, or if you touch the pin with a screwdriver after startup, the signal strength drops by 20 dB.

 


So, if you run into the same problem, disconnect everything from pin 21. To be on the safe side, you could even desolder the pin itself.

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