2025-12-21 7:18 AM - edited 2025-12-22 6:41 AM
Problem
When i call
* USBPD_PE_SVDM_RequestAttention
I get a OK message response but the callback never gets called.
* USBPD_VDM_SendAttention
Curious to know if there's any good way to debug this?
Current debugging steps
I have a STM32G0-Disco board setup to capture the messages over USB-PD and display them with ST's USB-PD monitoring software. So i know the attention pin is not currently activating. I have a breakpoint to make sure that USBPD_PE_SVDM_RequestAttention is being called. If i wait a few seconds and then trigger it to call USBPD_PE_SVDM_RequestAttention again i get a BUSY error. So i figure it's trying to send it, it just can't?
My project
I'm using this as my base with a stm32G071- nucleo board. I grab the CC lines from usb with a breakout board that passes the USB datalines through.
And i'm migrating all the USB-PD calls that relate to Display Port/VDM over from this project
PD captures
2025-12-24 6:14 AM
Hello @Brenden_PLUS
Thank you for your feedback!
Would you check if the callbacks are properly implemented as in G0 demo?
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2025-12-26 12:25 PM - edited 2025-12-26 12:34 PM
So i call the function USBPD_PE_SVDM_RequestAttention.
But it never fires the callback USBPD_VDM_SendAttention.
I thank you for your support, but i'll be on vacation till January 15. @FBL you been a huge help for me to figure out USB PD with the stm32.
2025-12-30 1:41 AM
Thank you @Brenden_PLUS It 's a pleasure to support you ! Enjoy your vacation.
Attention message can only be sent after a successful USB PD explicit contract and after entering the DisplayPort Alternate Mode. When HPD pin is low, and mode is not entered, the stack may silently ignore or queue the Attention message without sending.
I found also according to USB Type-C™ and Power Delivery DisplayPort Alternate Mode, section 4.6, an Attention message with IRQ set to 1 marks the end of USB PD DP Alternate Mode communication and the
beginning of standard DP operation, when all the DP signals are mapped to the Type-C connections.
An internal ticket 224463 is submitted to dedicated team for any insights into internal precompiled library management of USBPD_PE_SVDM_RequestAttention.
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