USBPD library: Source capabilities sent multiple times

[ChristophR]

Hi,

I have implemented a USB-C PD source using STM32CubeMX and the USBPD middleware. When looking at the trace from TRACER_EMB, I can see that the SRC_CAPABILITIES are sent multiple times:

When analyzing it with the STM32G071B-Disco as sink, the SRC_CAPABILITIES are shown only once:

What could be the reason for this behavior?

Thanks!

[Nicolas P. · Accepted solution]

Hello.

A quick explanation could be that the first source capability message wasn't received (corruption during the transmission or sink not ready at that time ?) :

we can see that there is only one GoodCRC in return.

Nicolas

[ChristophR]

Thanks.

I think you are right, the sink is not ready at that time. If I request the source capabilities later, the source sends the capabilities only once.