Removing CP2104 from dev board causes crash in WiFi.begin()

[chewwy]

I have been banging my head on this for a few days now, and need some fresh perspective on this problem.

Basically, I am using a ESP32 D1 Mini dev board, and programming it using Arduino.

I removed the CP2104 UART module using a hot air gun to see how much power I can save without it.

After removing the module, I am able to program it using a FTDI programmer. I am also able to run some test codes on it, even ones involving ULP.

However, the moment I use WiFi.begin(), the board crashes. I have looked at the schematic for the board, and I can't figure out how removing the UART module will affect WiFi.

Any ideas? Thanks!

[WiFive]

Did you remove the auto reset circuit?

[chewwy]

Could you please elaborate? What do you mean by the auto-reset circuit?

The reset button still works though..

[chewwy]

I removed the UMH3N module from the board, which is providing signal for EN and IO0.

No difference. I could read stuff from sensors, and write output by flashing LEDs.

But the moment I call WiFi.begin(), the board resets.

I am supplying 3.3V to the board via 18660 + HT7833 LDO. Everything works great until I removed the CP2104 UART module, so it shouldn't be insufficient power?

[chewwy]

I think I found the problem. It was indeed a power supply issue.

The LDO that I had the 3.3V pin hooked up to was dodgy, so it browned out when WiFi.begin() was called and there was a sudden demand for current. I hooked the circuit to a scope and discovered that.

Funny everything was OK when the CP2104 was still there (the circuit was hooked to the same LDO). But maybe it was bad luck and the LDO was on its way out.

I hooked the 18650 pin to the VCC pin (which passes the voltage through to the onboard ME6211 regulator, and everything worked again.