No USB enumeration on Seeed Fusion PCBA order

Products & Technology XIAO
1

Hi all,

I received a 5-unit PCBA order from Seeed Fusion using the XIAO ESP32-C6 and none of the boards enumerate over USB. Looking for help diagnosing before I go further.

Symptoms

  • No device appears in Windows Device Manager (including hidden devices) or macOS System Report under any conditions
  • Espressif’s esptool-js WebUSB tool shows nothing in the device picker — no enumeration even bypassing OS drivers entirely
  • Red charging indicator light behaves correctly on all boards (turns on at plug-in, off after 30s with no battery)
  • 3.28V measured on the 3.3V rail

What I’ve tried

  • BOOT held + RESET tap on all boards — no change
  • Two different computers (Windows and Mac)
  • Verified cable and setup with an older XIAO ESP32-C6 prototype, which connects and enumerates normally on both machines
  • All 5 boards behave identically

What I know

  • The boards were fully assembled by Seeed Fusion — I did no soldering myself
  • The USB-C port and D+/D- lines are internal to the XIAO module, so my PCB design shouldn’t affect USB enumeration directly
  • I do have an LED on GPIO9 (BOOT pin) through a 330Ω resistor to GND — wondering if this could be relevant, though a locked bootloader state should still enumerate

Has anyone seen this before with Fusion-assembled XIAO boards? Could the modules have shipped blank or with something that prevents USB peripheral initialization entirely?

Thanks,

Isaac

2

I don’t think pulling the boot pin low for the LED is a good idea. Rather pull the led high and use an Active Low implementation…
To check, just remove your 330Ω resistor.

3

Hi, just clipped the resistor and still can’t get it to connect.

Good thinking on the active low implementation. I’ll switch over to that on the next rev… if I can figure out the connection issue!

4

Once you have removed the resistor, you will still need to do the Boot low and press Reset. Or hold Boot low when plugging in USB.

Then flash code and all should be OK after that.

5

I did try that, sadly.

I’m thinking my next step tomorrow will be to make a UART bridge with a working Xiao to bypass the USB.

6

Sorry to hear that. :thinking:

XIAO ESP32-C6 allows boot from D6/D7 (TXD/RXD) so that may be a good option for you.

Apart from that, without seeing the schematic, or PCB design, it’s quite difficult to determine the fault.