How to implement USB DPM, prevent hard reset

Nv7 · ‎2025-03-23

I tried following STM32 AN5418 but the EvaluateSinkCapabilities method is not getting called. I added debug prints everywhere in the code and here is what I am receiving:

1. VBusInit (this always happens)

2. DPM notification 104 (Stack init)

3. Cable detection

4. Unimplemented SetDataInfo 8 (USBPD_CORE_EXTENDED_CAPA)

5. SetDataInfo 6 (USBPD_CORE_DATATYPE_RCV_REQ_PDO

- I haven't implemented anything in this, but I had it print out what it received and it looked good (e.g. 5V 3A 9V 3A 20V 5A etc.)

6. Notification: 30 (USBPD_NOTIFY_HARDRESET_RX)

7. Hard reset callback

8. Device turns off, turns on a few seconds later and goes through this same loop

What do I need to implement to get this working? Is this just because all of my methods are unimplemented besides EvaluateSinkCapabilities and one of the cases in GetDataInfo? At what point/do I call USBPD_DPM_RequestMessageRequest?

FBL · ‎2025-03-25

Hi @Nv7

Would you describe your working environment? Would you attach your project?

USBPD_DPM_RequestMessageRequestfunction is used to send a power request to the source device based on the selected Source PDO and the prepared RDO. Check this example.

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Nv7 · ‎2025-03-26

https://github.com/TektiteBiz/charge2b Here is the code. It appears that RequestMessageRequest is unimplemented, as well as everything else. I am not sure how to implement these.

Looking at the example it seems that it is unimplemented there too. (https://github.com/STMicroelectronics/STM32CubeG0/blob/fa3123ccb654f447d3738b86740fb869b2701ace/Projects/STM32G081B-EVAL/Applications/USB-PD/USB-PD_Consumer_1port/Src/usbpd_dpm_user.c#L535)

USBPD_StatusTypeDef USBPD_DPM_RequestMessageRequest(uint8_t PortNum, uint8_t IndexSrcPDO, uint16_t RequestedVoltage)
{
  USBPD_StatusTypeDef _status = USBPD_ERROR;
/* USER CODE BEGIN USBPD_DPM_RequestMessageRequest */
  /* To be adapted to call the PE function */
  /*       _status = USBPD_PE_Send_Request(PortNum, rdo.d32, pdo_object);*/
  DPM_USER_DEBUG_TRACE(PortNum, "HELP: update USBPD_DPM_RequestMessageRequest");
/* USER CODE END USBPD_DPM_RequestMessageRequest */
  DPM_USER_ERROR_TRACE(PortNum, _status, "REQUEST not accepted by the stack");
  return _status;
}

Nv7 · ‎2025-03-26

I tried adding a request through USBPD_PE_Send_Request inside of SetDataInfo because that successfully receives the source capabilities, whereas the EvaluateSinkCapabilities function is never called (not sure why). The device still receives notification 30 - HARDRESET_RX and then gets power cycled.

Do you have any idea on what could be causing the hard reset message - perhaps a protocol violation I am unaware of? Do you know why EvaluateSinkCapabilities isn't getting called?