Using USB-C Super Speed Alternate signals...

[Nick Breimer]

Hi

I am playing with USB-C

USB-C has 4 differential pairs, so called super speed channels, that is enabled in USB Alternate Mode

I am considering using them for my own signals between own design equipment, but of course still complying with the direction of the signals (so in my system I will always use an USB defined RX pin feeding a TX signal onto that line. I will keep signals on max 3.3V levels to comply with the standard

That way, if I ever connect the USB-C cable to a PC, I wont destroy anything

Also, I will add a protection device to handle the 20V that a USB-C port can deliver, if it is negotiated to do so (it might be that a port by mistake is negotiated to do that, and I don\'t want that to create problems also). So you guess correctly, I am also using VBUS to power the device

Do you see any problems doing that?

Thanks

Nick

 

[Klaus Kragelund]

On 28-11-2020 00:46, Nick Breimer wrote:

Hi

I am playing with USB-C

USB-C has 4 differential pairs, so called super speed channels, that is enabled in USB Alternate Mode

I am considering using them for my own signals between own design equipment, but of course still complying with the direction of the signals (so in my system I will always use an USB defined RX pin feeding a TX signal onto that line. I will keep signals on max 3.3V levels to comply with the standard

That way, if I ever connect the USB-C cable to a PC, I wont destroy anything

Also, I will add a protection device to handle the 20V that a USB-C port can deliver, if it is negotiated to do so (it might be that a port by mistake is negotiated to do that, and I don\'t want that to create problems also). So you guess correctly, I am also using VBUS to power the device

Do you see any problems doing that?

Thanks

Nick

I think that should be ok

AFAIK alternate mode is enabled with enumeration and negotiation with
the USB2.0 D+/D- channel

And thos signals will not change direction. Notice that is you connect
to a HDMI, DisplayPort, MHL or Thunderbolt port, you may get garbage in.
So you need to have safe SW \"behind\" those pins, so not to trigger
erratic behavior in the SW