USB_Device/HID_Standalone Example project crashes on USB disconnect on B-L475E-IOT01A2

[exceptionthrower]

Hi, I have a B-L475E-IOT01A2 board and I would like to implement an USB HID application on it. I use the example project found in the Github repository [1]. The application compiles and the USB device is detected on my computer as an input device. The problem is that upon a USB disconnect, the PC seems to jump to 0x0. When plugging the USB cable in again, the application runs again, but it seems I cannot run any code (in, e.g., the main while loop) after a USB disconnect interrupt while the cable is disconnected.

I see this problem both with STM32CubeIDE with ST-Link as well as with SEGGER j-link and Ozone.

In Ozone, I can set a breakpoint in the PCD Interrupt Handler for disconnect events (using USB_OTG_GINTSTS_OTGINT), which will trip upon disconnect. If I step through, I can finish HAL_PCD_IRQHandler to get back to OTG_FS_IRQHandler. As far as I can see, the PC clears to 0x0 after the POP {R7, PC} instruction which returns from the exception handler "OTG_FS_IRQHandler".

It can also be seen visually if I toggle an LED in the main while loop. After a USB disconnect, the blinking stops.

Steps to reproduce:

- Clone [1]

- Open STM32CubeIDE, go to File->Import

- Select 'Existing Projects into Workspace', Click Next and navigate to STM32CubeL4/Projects/B-L475E-IOT01A/Applications/USB_Device/HID_Standalone in the Git repo

- Debug the project, run it and plug in the USB OTG cable

- The device will enumerate as "STMicroelectronics HID Joystick in FS Mode" and your mouse will move

- Now disconnect the USB OTG cable and pause the execution

- Disassembly will fail as the PC is at 0x0

Any help regarding this issue would be greatly appreciated.

Thank you.

[1] https://github.com/STMicroelectronics/STM32CubeL4

[Saket_Om]

Hello @exceptionthrower

Thank you for bringing the issue to our attention. I have reported it internally.

Internal ticket number: 178547 (This is an internal tracking number and is not accessible or usable by customers).

[Saket_Om]

Hello @exceptionthrower 

The issue you raised has been addressed and resolved internally. The fix will be integrated in an upcoming release. Thank you again for your contribution.

[Saket_Om]

Hello @exceptionthrower 

To resolve the issue, you should remove the 100ms delay (line 6 in the code below) in the HAL_PCD_SuspendCallback function located in the usbd_conf.c file.

void HAL_PCD_SuspendCallback(PCD_HandleTypeDef *hpcd)
{
  __HAL_PCD_GATE_PHYCLOCK(hpcd);
  USBD_LL_Suspend(hpcd->pData);

   HAL_Delay(100);

    /*Enter in STOP mode */
  if (hpcd->Init.low_power_enable)
  {
    /* Set SLEEPDEEP bit and SleepOnExit of Cortex System Control Register */
    SCB->SCR |= (uint32_t)((uint32_t)(SCB_SCR_SLEEPDEEP_Msk | SCB_SCR_SLEEPONEXIT_Msk));
  }
}

[exceptionthrower]

Hello @Saket_Om

Thank you for your reply.

I replicated the step above and removed the delay in the callback function (in a freshly cloned and compiled repository).

Unfortunately, the problem persists.

Thanks,

exceptionthrower

[Saket_Om · Accepted solution]

Hello @exceptionthrower 

The USB device is currently operating in low power mode, which limits its ability to perform debugging. To enable debugging, the low-power mode must be disabled. This can be achieved by adjusting the initialization settings in the `USBD_LL_Init()` function, available in the `usbd_conf.c` file.

Please refer to the code below for the exact changes that need to be made (line 13).

/**
  * @brief  Initializes the Low Level portion of the Device driver.
  * @param  pdev: Device handle
  * @retval USBD Status
  */
USBD_StatusTypeDef USBD_LL_Init(USBD_HandleTypeDef *pdev)
{
  /* Set LL Driver parameters */
  hpcd.Instance = USB_OTG_FS;
  hpcd.Init.dev_endpoints = 5;
  hpcd.Init.use_dedicated_ep1 = 0;
  hpcd.Init.dma_enable = 0;
  hpcd.Init.low_power_enable = 0;
  hpcd.Init.lpm_enable = 0;
  hpcd.Init.battery_charging_enable = 0;
  hpcd.Init.phy_itface = PCD_PHY_EMBEDDED;
  hpcd.Init.Sof_enable = 0;
  hpcd.Init.speed = PCD_SPEED_FULL;
  hpcd.Init.vbus_sensing_enable = 1;
  /* Link The driver to the stack */
  hpcd.pData = pdev;
  pdev->pData = &hpcd;
  /* Initialize LL Driver */
  HAL_PCD_Init(&hpcd);

  /* configure EPs FIFOs */
  HAL_PCDEx_SetRxFiFo(&hpcd, 0x80);
  HAL_PCDEx_SetTxFiFo(&hpcd, 0, 0x40);
  HAL_PCDEx_SetTxFiFo(&hpcd, 1, 0x80);

  return USBD_OK;
}