I'm trying to build my own custom PCB based on an ATSAMD21E chip. I made a PCB breakout for the ATSAMD21E that just supports the reset button, a 3.3V voltage regulator, and a couple of capacitors.
After building the PCB with a fresh ATSAMD21E from Digikey, I connected it over a Segger JLink, and then flashed a bootloader onto the chip successfully using Microchip Studio. The bootloader I am using was Adafruit's QtPy bootloader, which uses the same chip as I am, also without an external crystal, so I thought that would work.
Unfortunately at this point I just get an error message "USB Device Not Recognized" instead of seeing a new USB device show up as expected.
Here is the schematic for my PCB:
I mostly just copied this from Adafruit's schematic for the QtPy. I followed these instructions:
https://learn.adafruit.com/how-to-progr ... ootloaders
for flashing the bootloader (which worked, I just can't see the USB port).
I have tried this with two different boards built from scratch with all separate components just in case it was a soldering problem, which did not solve the problem -- the second time the flashing of the bootloader worked fine again, and once again the USB device did not show up.
What am I doing wrong?
Building my own PCB based on QtPy schematic - USB not found
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- spolsky
- Posts: 2
- Joined: Thu Oct 11, 2018 6:47 pm
- danhalbert
- Posts: 4655
- Joined: Tue Aug 08, 2017 12:37 pm
Re: Building my own PCB based on QtPy schematic - USB not fo
You could try dumping the flash and verifying it looks like the flash on the QTPy. Also, make sure there are reasonable values for the fuses: if the fuses are set to all 1's, the board will trigger a watchdog reset every few seconds. There's a lot of discussion of fuse settings in the uf2 repo, e.g.: https://github.com/adafruit/uf2-samdx1/ ... -611128451
Other than that it's hard to say without debugging the board, making sure the design is OK, etc.
Other than that it's hard to say without debugging the board, making sure the design is OK, etc.
- spolsky
- Posts: 2
- Joined: Thu Oct 11, 2018 6:47 pm
Re: Building my own PCB based on QtPy schematic - USB not fo
Thanks for that advice! At this point I think there’s something wrong with my PCB design… but I can’t be sure. I definitely noticed that Lady Ada’s PCBs use much wider traces than I did, and I think the fact that some of my prototyping is on breadboards is causing problems too. I’m going to try designing a new PCB more carefully and see if that helps!
Please be positive and constructive with your questions and comments.