My design uses the compute module 3+ board from the raspberry pi foundation. I used the FSUSB42MUX schematic from the CMIO board to have a slave/host USB port. My problem is the D+ and D- lines are not being pulled up to 3.3 V, they have been pulled up to 5 V. I am attaching both the PCB and schematic design incase anyone can see any easily visible issues that I can not. HDMI output is working fine, as well as the SD card lines. All USB traces have been routed as 90 Ohm differential pairs.

Please let me know if more information is required.

PCB Schematic

FSUSB42MUX Schematic

CM3+ SODIMM Schematic

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    \$\begingroup\$ You don't ask aquestion, but having USB data lines pulled to 5V is simply wrong. And there is nothing on those picures that would explain what pulls them to 5V, the problem must be somewhere else. \$\endgroup\$ – Justme Mar 27 at 8:46
  • \$\begingroup\$ Likely problem with your circuit is that control signals to FSUSB42MUX (SEL) is likely exposed to +5V through some path, either via broken 7002 transistor, or else. Did you check all voltages on FSUSB42MUX pins? What are they? \$\endgroup\$ – Ale..chenski Mar 27 at 17:46
  • \$\begingroup\$ Hi Ale, I first probed the SEL and OE lines on the FSUSB42MUX. Couldn't find any issues there so it got me thinking about the differential signals. I probed the differential signal using my scope and things looked a little wonky on the data lines. I then proceeded to insert a new CM3 chip into the custom PCB, and things worked fine. I must have fried the other CM3's USB lines while testing. Thanks for reaching out! \$\endgroup\$ – Adam Heffernan-Munro Mar 28 at 17:30

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