Electrical – Help with Atmega32u4 custom PCB


I have attempted to design my own custom Atmega32u4 board, but when I assembled it it didn't show up in windows device manager. I fixed the problem where I forgot to connect VBUS to VCC with a jumper but it still doesn't show up in device manager. I have also measured all the power rails and made sure that everything got 5v. Any help would be much appreciated. enter image description here

Best Answer

220 Ohms, if your schematic represents what you have on the board is too high. You should be using ~22 Ohm for USB 2.0 edit: As noted by below, your schematic is correct here, just interesting notation and I misread.

It looks like you are basing this off of https://github.com/Dr-Derivative/Goldfish/blob/master/doc/goldfish.pdf

You should examine the key differences here. Notably:

  • CC1/CC2 are not terminated

  • You have unconnected VBus lines on your connector
  • You have unconnected D-/D+ lines on your connector
  • Your ATMega is insufficiently bypassed by capacitors on the power input.

The CC1/CC2 not being terminated is the biggest issue. The CC lines are how USB-C determines connectivity and orientation. Without them, your system won't attach as it doesn't know which way you've inserted the connector.