USBPD EPR Source

[xGloooM]

Hi, I'm trying to implement USBPD EPR Source with DisplayPort Alt Mode on a STM32G071.

I use the latest https://github.com/STMicroelectronics/stm32-mw-usbpd-core, which seems to support EPR, but I couldn't find any complete examples with a working EPR source.

Now I successfully enter EPR mode, and Sink receives EPR PDOs, but can't negotiate any PDO except the 1st. Even SPR PDOs

The stack sends REJECT after PE_SRC_NEGOTIATE_CAPABILITY.

It works perfectly in SPR mode and can switch between PDOs, but fails the same PDO in EPR mode

1st PDO in EPR mode ACCEPT:

2nd PDO REJECT:

How can I debug these things inside the stack? What am I missing?

Spoiler

uint32_t PORT0_PDO_ListSRC[USBPD_MAX_NB_PDO] =
{
  /* PDO 1 */
  (
    USBPD_PDO_TYPE_FIXED                 | /* Fixed supply PDO            */

    USBPD_PDO_SRC_FIXED_SET_VOLTAGE(5000U)         | /* Voltage in mV               */
    USBPD_PDO_SRC_FIXED_SET_MAX_CURRENT(1000U)     | /* Max current in mA           */
    USBPD_PDO_SRC_FIXED_PEAKCURRENT_EQUAL          | /* Peak Current info           */

    /* Common definitions applicable to all PDOs, defined only in PDO 1 */
    USBPD_PDO_SRC_FIXED_EPR_SUPPORTED              | /* EPR Mode Capable            */
    USBPD_PDO_SRC_FIXED_UNCHUNK_SUPPORTED      | /* Unchunked Extended Messages */
    USBPD_PDO_SRC_FIXED_DRD_SUPPORTED          | /* Dual-Role Data              */
    USBPD_PDO_SRC_FIXED_USBCOMM_NOT_SUPPORTED      | /* USB Communications          */
    USBPD_PDO_SRC_FIXED_EXT_POWER_NOT_AVAILABLE    | /* External Power              */
    USBPD_PDO_SRC_FIXED_USBSUSPEND_NOT_SUPPORTED   | /* USB Suspend Supported		 */
    USBPD_PDO_SRC_FIXED_DRP_SUPPORTED            /* Dual-Role Power             */
  ),
  /* PDO 2 */
  (
    USBPD_PDO_TYPE_FIXED                        | /* Fixed supply                */

    USBPD_PDO_SRC_FIXED_SET_VOLTAGE(9000U)         | /* Voltage in mV               */
    USBPD_PDO_SRC_FIXED_SET_MAX_CURRENT(3000U)     | /* Max current in mA           */
    USBPD_PDO_SRC_FIXED_PEAKCURRENT_EQUAL            /* Peak Current info           */
  ),

[xGloooM · Accepted solution]

After creating a topic, I found my bad in USBPD_PWR_IF_SearchRequestedPDO while in EPR mode. 

Would be nice to have an EPR Source example from ST.

[xGloooM]

ERROR with Trace_Notif :78

Also, sometimes got this message from the stack. Where can I find what 78 means?

[FBL]

Hi @xGloooM 

To create EPR request STM32 as source:

1. Initialize EPR PDOs properly by creating your EPR Source PDO PORT0_PDO_ListEPRSRC following the USB PD3.1 (or 3.2 depending on your stack, as of now I guess we support only 3.1) AVS PDO format (voltage in 25 mV units, current in 50 mA units).

2. Assign this PORT0_PDO_ListEPRSRC and its count to the EPR PDO storage in USBPD_PWR_IF_Init.

3. Enable EPR Source support in DPM_Settings for the port to inform the PE and stack .Is_EPR_Supported_src=USBPD_TRUE,

4. Ensure USBPD_PWR_IF_GetPortPDOs supports USBPD_CORE_DATATYPE_SRC_PDO_EPR to handle PDO retrieval for EPR.

5. In USBPD_PWR_IF_SearchRequestedPDO, check if the requested RDO position corresponds to an EPR PDO.

6. In USBPD_PWR_IF_SetProfile,  set voltage/current to process the selected PDO type when the device receives a power contract request RDO to handle EPR voltages and currents properly (up to ~48 V).

About the error message from trace, it means nothing, you have just received the status.