Hands-On RTOS with Microcontrollers

The USB virtual comm driver

The USB's receiving StreamBuffer is populated by CDC_Receive_FS() in Drivers/HandsOnRTOS/usbd_cdc_if.c. This will look similar to the code from Chapter 11, Sharing Hardware Peripherals across Tasks, where the transmit side of the driver was developed:

static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t *Len){  /* USER CODE BEGIN 6 */  portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;  USBD_CDC_SetRxBuffer(&hUsbDeviceFS, &Buf[0]);  xStreamBufferSendFromISR( *GetUsbRxStreamBuff(),        Buf,        *Len,        &xHigherPriorityTaskWoken);  USBD_CDC_ReceivePacket(&hUsbDeviceFS);  portYIELD_FROM_ISR(xHigherPriorityTaskWoken);  return (USBD_OK);  /* USER CODE END 6 */}

Using a stream buffer instead of a queue allows larger blocks of memory to ...