FEDEVEL
Platform forum

, 05-19-2024, 12:49 PM

Hello,
I would like to ask if I can do this? ... check the pictures.
I want to use MUX HD3SS3212 but location of the pins are not good for my layout. So, I swapped some lines (swapping +/- is allowed, right?!). I swapped usbC TX1 pins and swapped RX1 pins too. Also, I swapped TX and RX which going from MUX to USB Hub controller. Is it OK, that I did many swapping?

Also I swapped portB and portC of HD3SS3212 to improvement routing. In datasheet they connect portB to RX1/TX1 usbC pins. I connected portB to RX2/TX2 pins. Could I did this? In my opinion, YES. Because, I only will need to control MUX SEL pin with inverting signal to connect the right pair of TX/RX lines.

Also, what about AC coupling capacitors... Should I use it between MUX and USB-C connector on TX lines and between MUX and USB Hub controller too? Give me some recommendation please.

Thank you.
Regards,
Martin

QDrives , 05-19-2024, 02:25 PM

From the little I know on USB3, simple answers:
- Can you swap + and - --> NO unless the datasheet of the HD3SS3212 **clearly **states so.
- Can you swap Rx/Tx 1 with Rx/Tx2 --> Yes, but I recall that you need to swap more than just those two. CCx or Vbus pins are used to select which (should) be connected, so they too may need to be swapped. You could simply see this as the USB C connector having two side, swap all pins of one side to another, and it should work.

, 05-19-2024, 04:51 PM

Hi @QDrives, sorry for my bad explanation. You are right, D+/- not allowed to swap. RX, TX +/- are allowed to swap. I wrote it bad in previous post but I thought it right. 🙃
I agree with that CC1 "is connected" with RX1/TX1 - that is, with the first row of usbC and CC2 is for second row of pins.

QDrives , 05-19-2024, 08:42 PM

I see that HD3SS3212 is just a Mux/Demux. For that chip it will not matter Tx/Rx + or -.
However, the USB controller that it is connected to, then must support the swap as well, unless you swap the output (or is it input) of HD3SS3212 also.

, 05-20-2024, 08:20 AM

I want to use USB7206C and it support TX, RX +/- swapping. Thank you for information.