Hello, I’m using the samd21G18A device in a custom PCB. I’ve included the main bit of my schematic. Basically, when I program the bootloader (I have a 10 pin connector on the board) using an Atmel-ICE and Atmel Studio, it works fine. The bootloader loads, but then the device never enumerates as a usb device for me to load my main sketch.
I’ve tried a few bootloaders including the ones for the zero, sparkfun’s samd21 breakout, and ones from here: ArduinoCore-samd/bootloaders/zero at master · arduino/ArduinoCore-samd · GitHub, and they all work about the same. They program just fine, but never enumerate.
Sparkfun’s bootloader uses the built in LED, which is helpful. With that I’ve been able to verify that when I press the reset button (ground the reset pin), the LED goes off since the bootloader is not driving it. So I have confidence in my reset pin.
I’ve replaced the samd21, the crystal, and all the IC’s involved in deriving 3.3V, and none of these steps have led to any changes.
My best guess at the problem is the crystal, just because I am pretty sure a bad crystal will lead to no issues with programming, but will lead to usb communication issues.
A suggestions for debugging this?