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Custom PCB with ESP32-S3 won't start, but I can upload firmware

Posted: Mon Jun 16, 2025 12:53 pm
by aribao
Hello,
I have created my first custom PCB with an ESP32.

I received the PCBs today, and they don't work. I can flash the firmware. I tried it with WLED and the typical "hello_world" example. But it won't start. Nothing is shown on the serial monitor.

Everything looks fine; the power is ok, but it's not starting.

I can get the chip info and the mac info, but it never runs the program.

For WLED, the wifi AP is never created, and for the "hello_world" nothing is shown in the monitor.

Is there any way to find out what is happening?

If I reset the device, what I see is this:

Code: Select all

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0x0 (DOWNLOAD(USB/UART0))
Saved PC:0x40041a76
waiting for download
I attach the screenshots of the schematic.

Code: Select all

esptool.py v4.8.1
Serial port /dev/ttyACM0:
Connecting...
Detecting chip type... ESP32-S3
Connected to ESP32-S3 on /dev/ttyACM0:
Chip type:          ESP32-S3 (QFN56) (revision v0.2)
Features:           Wi-Fi, BT 5 (LE), Dual Core + LP Core, 240MHz, Embedded Flash 8MB (GD)
Crystal frequency:  40MHz
USB mode:           USB-Serial/JTAG
MAC:                f0:f5:bd:51:cd:3c

Uploading stub flasher...
Running stub flasher...
Stub flasher running.

Flash Memory Information:
=========================
Manufacturer: c8
Device: 4017
Detected flash size: 8MB
Flash type set in eFuse: quad (4 data lines)
Flash voltage set by eFuse: 3.3V

Hard resetting via RTS pin...
Thank you very much

Re: Custom PCB with ESP32-S3 won't start, but I can upload firmware

Posted: Tue Jun 17, 2025 12:36 pm
by Sprite
IO0 somehow is kept low. I don't see anything in your schematic that does this; perhaps you have a short, or some conducting flux residue left in place?