I have been designing my own PCB using the atsam3x8e chip, the same as the Arduino due which I used to prototype with. So far I've managed to get my boards up and running by programming them via the serial TX & RX pins using a USB to serial converter, but I can't seem to get the "Native" USB port to work in windows.

When the boards are plugged in, they show up in the windows device manager as "Unknown USB Device (Device Descriptor Request Failed)" but do not show up in BOSSA or Atmel Studio 7.0. My understanding was that when the chip is reset and erased, it should just show up as a "BOSSA programming port" the same as the Arduino DUE does when it is put through the same procedure. I'm not sure whether this is an issue with the hardware design of the board or not. I have used a USB C connector instead of a Micro USB so have not connected the UOTGID pin and instead added two pulldown resistors to the CC pins on the new connector.

If anyone has any suggestions on this please let me know.

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  • "do not show up in BOSSA or Atmel Studio 7.0" is a consequence of "Unknown USB Device (Device Descriptor Request Failed)", not so much additional information. Your understanding about it showing up as USB when erased is correct. Show the hardware design.
    – timemage
    Dec 2, 2020 at 22:21
  • added @timemage Dec 2, 2020 at 22:33
  • I'm not terribly familiar with USB-C pinout, and it's hard to read just the PCB layout, but if I take it for granted that your two parallel traces are the D+ and D-, they go to only the high speed pins and not the full speed pins. The due design does both.
    – timemage
    Dec 2, 2020 at 23:08
  • @timemage this USB port is fairly simple, its 2.0 spec with VBUS, GND, DATA +, DATA- and CC pins instead of the ID pins. You're correct about the parallel traces being the data lines but they're connected to the high-speed pins directly and the full speed pins with 30k ohm resistors R22and R23. Dec 3, 2020 at 7:00
  • Trying a different USB C cable and programming the boards over serial with an Arduino sketch makes the boards appear as Arduino DUE, but when reset and erased after this, the boards are still coming up as Unknown USB Device, is this normal behaviour since the vendor ID and Product ID are different? Dec 3, 2020 at 8:36


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