Use custom VDMs messages for out-of-band messaging between two CCGx devices.

[OlEr_1999891]

Hi!

We have a scenario where we are looking at connecting custom USB-C devices downstream from our USB-C dock (with USB-C downstream as well). We would like to send / receive some system messaging between these two units (they run CCG4 and CCG3) using the CC lines since USB/DP is managed by the connected laptop etc.

We would like to be able to send and intercept the messages both internally in the CCGx FW and via the HPI-interface, if possible.

Is this possible? If yes, could you give a quick summary of which EZ-PD API to use, HPI commands and any things to consider so that the messages will not interfere with the normal PD-messaging?

Cheers

Olof

[Sananya_14 · Accepted solution]

Hi Olof,

Yes, you could add your custom VDM commands between the dock and the device in the firmware after the PD contract is completed. You could use the dpm_pd_command() API with DPM_CMD_SEND_VDM parameter and your custom command. Please refer to section 6.3.8 in the CCGx Host SDK User Guide for details on the VDM handling in the existing firmware.

For using the HPI interface to send VDMs, kindly create a Tech Support case for further discussion on this since the specification is not released on the web.

Best Regards,

Sananya