FEDEVEL
Platform forum

Bob , 10-07-2025, 06:34 PM

I'm routing a USB3.0 type C connector to RPI CM5 pads and i have absolutely no idea how to route these crossed USB-C traces. I'm on a 6-layer board and I've attached a screenshot of my absolutely cursed attempt. I do have solid GND plane on layer 2 and 5. I just dont understand how to optimally route these signals and avoid doing all this VIAing and detangling, it's just gross and I need to do a lot of intra&inter length matching. Also I find kicad differential pair router to be super buggy so if any1 have any tips for routing differential pairs in kicad lmk.

Bob , 10-07-2025, 06:35 PM

Bob , 10-07-2025, 06:36 PM

its actually so cursed

corlas , 10-07-2025, 07:18 PM

First of all, for USB-C superspeed you should use USB3 MUX, something like this: http://ti.com/lit/ds/symlink/hd3ss3202.pdf?ts=1759814171105

Bob , 10-07-2025, 07:35 PM

ohhhh I see thanks a lot

corlas , 10-07-2025, 07:38 PM

but for this one you also need USB type-c controller, its probably easier to use all in one package, something like this: https://www.ti.com/lit/ds/symlink/hd3ss3220.pdf?ts=1734478373768&ref_url=https%253A%252F%252Fwww2.mouser.com%252F

Bob , 10-07-2025, 07:44 PM

sorry if im asking dumb questions but why do I need type-c controller? I thought bc the CM5 has the CC0/CC1 pins itself, i can just wire any usb-C CCs to the CM5 directly ?

corlas , 10-07-2025, 07:50 PM

hm, these CC pins are probably just for power delivery, sometimes, when CC pins are directly connected to the SOM module, there is also pin for MUX control (output from SOM) but I don't think this is the case for CM5

corlas , 10-07-2025, 07:51 PM

but this is not common, usually CC pins are not connected to the SOM modules

Bob , 10-07-2025, 08:03 PM

ah i think i get it now
for example for USB2-C port I can simply connect CC pins directly to CM5 because it's just used to advertise power support (5V @ 5A in CM5's case)
but for USB3-C superspeed we need the mux now which needs to know the superspeed pairs' orientation and that would need a separate type-c controller
and i can just use the 2in1 package that includes controller to save space
am i understanding correctly?

corlas , 10-07-2025, 08:10 PM

Hmm, are you going to power it via this USB-C?

corlas , 10-07-2025, 08:12 PM

well yes but these controllers can usually request 5V/3A maximum => 15W. Thats the case for the one I sent above for example, if 15W is enough, this is probably the easiest solution.

Bob , 10-07-2025, 08:15 PM

USB2-C is able to power the CM5
this USB3-C port is for external periph so the CM5 is powering the periph