STM32L452RE -> USB CDC Transmit Stuck, hcdc->TxState Never Resets
Hello ST,
I'm developing a USB CDC communication project on an STM32L452RE microcontroller using STM32CubeIDE.
I can successfully receive data from a PC using the Hercules SETUP utility by HW-group.com.
I'm facing a challenge with transmitting data back to the PC using the CDC_Transmit_FS function.
Environment:
- MCU: STM32L452RE
- IDE: STM32CubeIDE
- CUBEMX: STM32CubeL4 Firmware Package V1.18.1
- USB Configuration: Configured as a CDC Virtual COM Port
- OS: Windows 11
- USB Interface: Hercules 3.2.8
Issue Description:
Data reception from the PC works flawlessly. However, when attempting to transmit data back using CDC_Transmit_FS, the function seems to never complete. The code gets indefinitely stuck waiting for hcdc->TxState to reset to 0, which, based on my understanding, should happen via an interrupt once the transmission completes.
Troubleshooting Done:
- Create a new ST board project using this video USB tutorial:
https://www.youtube.com/watch?v=92A98iEFmaA&t=212s - Confirmed correct USB descriptor configurations.
- Debugged to pinpoint that the halt occurs during data transmission, specifically waiting for hcdc->TxState.
- The hUsbDeviceFS.pClassData return the “USB Device handle structure” there is a USB communication problem with the device's startup as a result.
Questions:
- Are there any known issues with USB CDC on STM32L452RE that might cause this behaviour?
- Could there be any CubeMX configuration or USER CODE that I might have overlooked that could lead to this issue?
The computer recognizes the card on COM12:
|
BAUND 115200
Data bits 8
Parity None
Stop bits 1
Flow Control None
The Hercules SETUP utility opens the COM12, but the MCU does not send the object.
char *data ="HELLO LUMUS!\n" to the USB buffer.
Code Snippets:
main.c While loop:
/* USER CODE BEGIN 0 */
uint8_t ret =0;
char *data ="HELLO LUMUS!\n";
/* USER CODE END 0 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
ret = CDC_Transmit_FS((uint8_t *) data, strlen(data));
if(ret)
printf("CDC_Transmit_FS ERROR TYPE:%d",ret);
HAL_Delay(1000);
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
CDC Transmit Function:
uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len)
{
uint8_t result = USBD_OK;
/* USER CODE BEGIN 7 */
USBD_CDC_HandleTypeDef *hcdc = (USBD_CDC_HandleTypeDef*)hUsbDeviceFS.pClassData;
if (hcdc->TxState != 0){
return USBD_BUSY;
}
USBD_CDC_SetTxBuffer(&hUsbDeviceFS, Buf, Len);
result = USBD_CDC_TransmitPacket(&hUsbDeviceFS);
/* USER CODE END 7 */
return result;
}
Device Init for the USB:
void MX_USB_DEVICE_Init(void)
{
/* USER CODE BEGIN USB_DEVICE_Init_PreTreatment */
/* USER CODE END USB_DEVICE_Init_PreTreatment */
/* Init Device Library, add supported class and start the library. */
if (USBD_Init(&hUsbDeviceFS, &FS_Desc, DEVICE_FS) != USBD_OK)
{
Error_Handler();
}
if (USBD_RegisterClass(&hUsbDeviceFS, &USBD_CDC) != USBD_OK)
{
Error_Handler();
}
if (USBD_CDC_RegisterInterface(&hUsbDeviceFS, &USBD_Interface_fops_FS) != USBD_OK)
{
Error_Handler();
}
if (USBD_Start(&hUsbDeviceFS) != USBD_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USB_DEVICE_Init_PostTreatment */
/* USER CODE END USB_DEVICE_Init_PostTreatment */
}
The Register Class Link class driver to device core:
USBD_StatusTypeDef USBD_RegisterClass(USBD_HandleTypeDef *pdev, USBD_ClassTypeDef *pclass)
{
uint16_t len = 0U;
if (pclass == NULL)
{
#if (USBD_DEBUG_LEVEL > 1U)
USBD_ErrLog("Invalid Class handle");
#endif /* (USBD_DEBUG_LEVEL > 1U) */
return USBD_FAIL;
}
/* link the class to the USB Device handle */
pdev->pClass[0] = pclass;
/* Get Device Configuration Descriptor */
#ifdef USE_USB_HS
if (pdev->pClass[pdev->classId]->GetHSConfigDescriptor != NULL)
{
pdev->pConfDesc = (void *)pdev->pClass[pdev->classId]->GetHSConfigDescriptor(&len);
}
#else /* Default USE_USB_FS */
if (pdev->pClass[pdev->classId]->GetFSConfigDescriptor != NULL)
{
pdev->pConfDesc = (void *)pdev->pClass[pdev->classId]->GetFSConfigDescriptor(&len);
}
#endif /* USE_USB_FS */
/* Increment the NumClasses */
pdev->NumClasses++;
return USBD_OK;
}
The function USBD_RegisterClass returns USBD_OK, so I don’t know the root of the USB communication problem.
Any insights or recommendations would be immensely appreciated.
I appreciate your support!
Marom.