Anybody to have simple USB to at least be enumerated on STM32L462?

[fred bar]

Hi.

I am currently trying to have USB virtual com port to work on STM32L462CEU6. I made simplest project using IDE, just enabling usb then setting the usb class to be CDC. Nothing fancy, no more things than setting the 48mhz clock and flashing cpu. No usb is detected and the cabling is correct. USB is not detected on macos.

I tried same approach on a nucleo64 with a stm32L452, which is basically the same chip. Same procedure works, i get the device detected and configured.Tried flashing the 462 with 452 firmware and while flashing works, usb did not.

I checked my board and cables thousand times and i am sure it is ok. I get absolutely no signal on the DP and DM pins... at all...

Do you have any idea of what to test or bug reports to share?

Thanks.

[Tesla DeLorean · Accepted solution]

>>I checked my board and cables thousand times and i am sure it is ok.

Have someone less involved check it.

Double check VDDUSB

Check the netlist for connectivity of all appropriate nets, and that you don't have islands with subtly different naming or grounds

[fred bar]

First, thanks for the advice on getting someone else check. I am unfortunately the sole member of my team and company so unless i get multiple personality disorder or hire people, not likely to happen here. But i wish to and i agree that it should be a thing to do.

Other than that, you are damn right. I checked vddusb and saw that the device in eagle had a VSSUSB pin that was connected to gnd.... yep.. By the way it looks, library got imported from somewhere, did not create it myself. Fortunately, i could cut the track and give it a nice 3.3V. No wonders, it now works.

Thanks a great bunch.

Now i have a batch of boards to correct. Meh.