USB CDC Transmit Hangs Intermittently
Using CDC USB on STM32G4 FW version 1.5.2, Win10 with default VCP driver.
When calling CDC_Transmit_FS() from main() it will work for a few seconds and then hang indefinitely when TxState is never reset to 0. Others have had this issue (see: here, here) and reported the solution being interrupt priority. This is how I have my interrupts set:
Which seems right to me, nothing could overwrite the USB Tx interrupt - but the issue persists.
The project this is used in is more complex but this very simple program reproduces the issue:
relevant section of main.c:
uint8_t send_buf[APP_TX_DATA_SIZE];
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);
static void MX_SPI2_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_SPI1_Init();
MX_USB_Device_Init();
MX_SPI2_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
sprintf(send_buf, "Setting output of channel 10 to: 300.00000mA\n");
CDC_Transmit_FS(send_buf, strlen(send_buf));
}
/* USER CODE END 3 */
}CDC_Transmit_FS() in usbd_cdc_if.c:
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;
}After connecting to the VCP this will send the expected output for a few seconds and then will stop sending until hard reset.
Any ideas what I'm doing wrong?