I am currently using the STM32U585 MCU on a custom board and am trying to get the MCU to function as a DRP device in the USB-C PD protocol. Although currently I am just trying to get the device to work as a SNK (with DRP capability enabled). The project I am implementing this in is using ThreadX as the RTOS.
I have followed multiple tutorials for getting USB-C power delivery implemented on ST MCUs and have implemented the needed changes in the CubeMX .ioc file and have also made the necessary changes in the code listed in AN5418.
I have also referenced plenty of example projects including: DemoUCPD, USB-PD_Consumer_1port, USBPD_DRP_UX_DRD_HID, USBPD_SNK, and USBPD_SNK_UX_Device_HID_CDC_ACM.
One thing that is worth noting is our custom PCBs do not have the TCPP IC on our board, contrary to a lot of the examples. Also, a lot of examples also seem to use FreeRTOS, but the rest of our project has been using ThreadX, so didn't want to make the switch.
Here is what I have found so far, using this flow diagram as the expected sequence of events in a Sink Power negotiation:
-Device gets through initialization and reads the VBUS voltage correctly.
-When a USB-C cable is plugged in (USB-C to USB-C cable with USBPD capable power source) the program is able to enter the USBPD_DPM_SetDataInfo, but instead of entering with a USBPD_CORE_DataInfoType_TypeDef of USBPD_CORE_DATATYPE_RCV_SRC_PDO, it enters with USBPD_CORE_DATATYPE_RDO_POSITION and then with a subsequent call with USBPD_CORE_DATATYPE_RCV_REQ_PDO. It then repeats this a second time with nothing happening. This doesn't match the flow in the picture above.
-USBPD_DPM_SNK_EvaluateCapabilities is never called.
-I have used both the STM32 UCPD Monitor and a Cypress USB-PD monitor. All I see is that my device only ever sends zeroes back. I can see the USB-C power source sending the correct messages so I can confirm that the power source is working.
-Using a breakpoint in the code I can see that the code enters USBPD_PORT0_IRQHandler and correctly enters UCPD_SR_RXMSGEND when the USB-C cable is plugged in. I can also see a byte being received in my buffer, but can only see one byte at a time since that is the size of the UCPD RX register.
-I tried to look at the memory location where I would expect to see the full message received, but I only ever see zeroes (potentially a DMA issue?).
I have looked at multiple example projects and most of them seem to have the same file content between them. Since the SetDataInfo callback is being called with reasonable parameters and the IRQ handler is getting to RXMSGEND, I assume that we are possibly receiving data correctly, but I could be wrong.
I have tried just using the application in SNK mode rather than as a DRP, and I have gotten the same results.
Any help or hints would be greatly appreciated.
