Hi everyone,
I'm working on a system using USB Power Delivery (PD) and am struggling to understand the specifications/features. Maybe someone here has experience with USB PD signalling/communication.
I have a USB PD source capable of 5V and 20V. I want my powered device to request 20V, but
only after it has identified the power source as a particular product ID/serial number. Basically, the powered device has to "authenticate" the source as "genuine" first. A typical PD system doesn't care about this. If the powered device needs high power, it will select the highest-power profile advertised by the source, no questions asked.
I've spent a few hours now, searching through the USB PD spec, and some white papers published by IC manufacturers. One thing that caught my eye was "Vendor Defined Messages" (VDMs). These messages are allowed to contain information not explicitly defined in the USB specification. My question is: Can I use VDMs to interrogate the power source for some sort of product ID?
Both the source and the device are custom. I would imagine I couldn't use off-the-shelf USB PD controllers. Think I would have to use a micro-controller to implement the USB PD stack + additional VDM signalling.
Any thoughts on the feasibility of this? Maybe it's better off to send some data over D+ /D- separately.
Thanks.
