AM67A: USB OTG functionality

Hi Michael 

Michael Walle said:

Does the SoC supports OTG on USB0?

USB 0 does support OTG mode, in the linux sdk we have configured usb0 as OTG.

Michael Walle said:

Also, can both USB0 and USB1 be used with SERDES0 (of course only one can be used at the same time). Or is SERDES0 hardwired to a certain USB controller?

Only USB1 can be used with serdes.

Michael Walle said:

For this configuration, we have USB0 routed to the USB2.0 port, USB1 and SERDES0 to the USB3.2 port and SERDES1 to the PCIe port. Can you confirm, this will work?

This configuration should work , if you see the schematic of the J722S evm we are also having similar configuration.

Regards
Diwakar

Hi Diwakar,

Diwakar Dhyani said:

USB 0 does support OTG mode, in the linux sdk we have configured usb0 as OTG.

I've seen that but how does the role switch work? In your EVM schematics there's a DIP switch to switch roles. But that is not OTG that is just host and device mode. That is also where my second question comes into play: "Also, I guess the USB_ID pins should (or can) just be connected to any GPIO?"

Also, why does the TRM says OTG is not supported (pg 479, SPRUJB3, March 2024):

4.10.4.1 USB2SS Unsupported Features
* On-The-Go (OTG)

Diwakar Dhyani said:

Only USB1 can be used with serdes.

Thanks for confirming!

Best regards,
Michael Walle

Hi Michael,

I am gathering more detail on this internally , will respond once we hear back from internal team.

Regards
Diwakar

Hi Diwakar,

honestly, that's a bummer. Could you please find out what's the difference between DRD and OTG?

Best regards,
Michael Walle

Hi Michael

Please refer to one of the older response to understand the diffrence.

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1005511/am6548-difference-between-otg-and-dual-role-mode

Regards
Diwakar

Hi Diwakar,

This still doesn't answer my initial question, where do I connect the USB_ID pin. When I look at the referred AM6548, it has a dedicated USB_ID pin which the AM67A doesn't have.

Thanks,
Michael Walle

Hi Michael

Michael Walle said:

This still doesn't answer my initial question, where do I connect the USB_ID pin. When I look at the referred AM6548, it has a dedicated USB_ID pin which the AM67A doesn't have.

If you see the response, it is clearly mentioned that USB_ID pin is not required for DRD mode which is supported by the AM67 as Role negotiation is done in software.

Regards
Diwakar

Hi Diwakar,

excuse my ignorance. But how does role switching work in that case? As I've mentioned we cannot hardcode the role in software.

Best regards,

Michael Walle

Hi Michael

Can you help me understand the use-case so that we can guide you in better way.

Regards
Diwakar

Hi Diwakar,

USB0 should be able to be either USB host or USB device depending on the USB_ID signal, which might change during runtime (of course).

Thanks,
Michael Walle

Yes, thanks for confirming.