Failed to connect to ESP32-S3: No serial data received

1

Hello there,
I designed a custom pcb using espressif doc for the devkit esp32 s3. I had a few issues where at the beginning I had to use a different port and a different cable till it worked, then I had an issue with the auto boot mode which i solved by adding a 10uF cap. It was working like charm and no problems, until a few tests later and uploading the code, the esp stopped uploading with the following error A fatal error occurred: Failed to connect to ESP32-S3: No serial data received.

For troubleshooting steps visit: https://docs.espressif.com/projects/esptool/en/latest/troubleshooting.html

*** [upload] Error 2

I did try shorting gpio 0, then short the chip pu briefly and upload, reduce upload speed but all in vain. When I open the serial monitor i see output from the esp. When i try the manual reset, once the pc tries to connect to the esp, as soon as i disconnect gpio 0 from ground the code starts executing and the upload fails. Any thoughts or solutions?

2

Since it is a custom board that only you know exactly, it would be helpful to provide the schematics! This may help others to be able to help you.

Which interfaces do you use?

  • UART (with a UART to USB converter chip like the CH340 / CP2102)
  • Native USB interface of the ESP32-S3?
3

Screenshot 2025-12-15 170952
Screenshot 2025-12-15 1709521268×944 100 KB

Its a custom pcb but its based on espressif schematics.

As of the interface, I am doing it using UART with cp2102 chip

4

Is the board recognized by the PC?
Have you tried it with the native USB interface / does the same error occur there?

5

yes, it is recognized. It prints on the serial monitor output from the esp. As of the native, I disabled it because i wanted to use the esp as a host

6

Also GPIO 46 is a strapping pin and must be pulled low when uploading a new firmware.

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See https://documentation.espressif.com/api/resource/doc/file/rz94aWY3/FILE/esp32-s3_datasheet_en.pdf