USB3.x schematic and layout issue

hello, i tryed to get usb3.x working on iMX8MM but the driver tells me maybe the cable is bad. Basically 100nF Caps had to be placed in the SSTX signals close to sender. Are they on the SOM module placed? for the next hardware revision i try to improve the layout for high speed. On the Verdin Evo Board the caps are only placed on the SSTX signals coming from the USB hub. maybe someone have a hint for me. thx Franz

A Verdin iMX8M Mini (iMX8MM) module has no USB 3.0. Only USB 2.0 supported. Please check its datasheet for details.

Hello, you are right, we use the iMX8MP module. sorry for confusing you.

The USB_1_SSTX and USB_2_SSTX lines have 220nF AC-coupling capacitors on a module.

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Are total caps on SSRX and SSTX to be matched in the USB specification? Because on the Dahlia board, SSTX lines of the USB hub have 100nF which then go to SoM module’s SSRX pins.

Yes they are. There are no coupling capacitors on module’s SSRX pins.

Yes I know, there is no cap on SSRX of the SoM. But there is 100nF on the carrier board (Dahlia) side. And similarly for SSTX, SoM has 220n and carrier board has 0. So in total TX has 220nF but RX has 100nF. So what I understand is that total caps on the SSTX and SSRX don’t need to be matched to each other. Is my understanding correct?

The AC coupling cap value came from the USB3 spec:

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