What might be causing a 2-3 second delay for Windows to recognize the XIAO SAMD21 board?

[dgsgsgdggg]

Sorry if this isn't the right place to ask, I have little experience with how microcontrollers and bootloaders work internally.

The XIAO SAMD21 board out of the box has a 2-3 second delay before it gets recognized on my Windows 11 laptop. I've tested this with 4 different XIAO SAMD21 boards. I've also built a new bootloader using this repo only changing the PID and VID definitions and there's the same 2-3 second delay.

The Adafruit QT Py - SAMD21, which is based on the XIAO version doesn't have this issue and gets recognized instantly when I plug it in.

Is this problem caused by the hardware differences between two of these boards, or is there something with the bootloader?

[dhalbert]

If you compare the board files for the two boards you will see some differences:. For instance, the QT Py is CRYSTALLESS, and starts up the clocks in a different way. The status LED is also different.

The bootloader goes to some lengths to make sure the voltage is stable and at a high enough value. If the XIAO has larger capacitors or something like that, that cause a slower voltage ramp up, that could also be an issue.

I would say try other builds that vary in the same way. The base bootloader is very similar. You could trying loading the QT Py bootloader on the XIAO to pretend it's CRYSTALLESS, and see if you see the same delay. The status LED won't work but it should otherwise come up. By doing various trials like this you could narrow down the difference.