USB CDC VCP help to receive Data from PC

[maxyork145]

Posted on July 09, 2013 at 20:09

Hello everybody (This about USB VCP)

i started an application to send and receive data from PC to STM32F4 discovery i used the titorial provided by STmicro, but the problem i'm not able to sent to the STM32F4Discovery (PC to STM32), only from Discovery to PC

i use this function to send to PC, she work fine, but i can't find how receive data from PC, anything can help me.

The function blow provide to send Data to PC ----------------------------------------------------------------------------------------------------------------

static uint16_t VCP_DataTx (uint8_t* Buf, uint32_t Len)

{   if (linecoding.datatype == 7)   {     APP_Rx_Buffer[APP_Rx_ptr_in] = USART_ReceiveData(EVAL_COM1) & 0x7F;   }   else if (linecoding.datatype == 8)   {     APP_Rx_Buffer[APP_Rx_ptr_in] = USART_ReceiveData(EVAL_COM1);   }     APP_Rx_ptr_in++;     /* To avoid buffer overflow */   if(APP_Rx_ptr_in == APP_RX_DATA_SIZE)   {     APP_Rx_ptr_in = 0;   }      return USBD_OK; } #usb-vcp-need-receive-function

[Tesla DeLorean]

Posted on July 09, 2013 at 20:23

As I recall I just had the VCP_DataRx() routine send data out the USART, but it could just as easily put it in a buffer.

[gvigelet2]

Posted on July 17, 2013 at 20:32

Clive is correct it is the following function that receives the data from the PC (via usb) and passes the data to the UART.

/**  * @brief  VCP_DataRx  *         Data received over USB OUT endpoint are sent over CDC interface   *         through this function.  *             *         @note  *         This function will block any OUT packet reception on USB endpoint   *         untill exiting this function. If you exit this function before transfer  *         is complete on CDC interface (ie. using DMA controller) it will result   *         in receiving more data while previous ones are still not sent.  *                   * @param  Buf: Buffer of data to be received  * @param  Len: Number of data received (in bytes)  * @retval Result of the opeartion: USBD_OK if all operations are OK else VCP_FAIL  */static uint16_t VCP_DataRx (uint8_t* Buf, uint32_t Len){  uint32_t i;    for (i = 0; i < Len; i++)  {    USART_SendData(EVAL_COM1, *(Buf + i) );    while(USART_GetFlagStatus(EVAL_COM1, USART_FLAG_TXE) == RESET);   }    return USBD_OK;}If you are looking for the trail the data travels, the data comes from the PC over usb which is handled by the USBD_CDC library through function usbd_cdc_DataOut /**  * @brief  usbd_cdc_DataOut  *         Data received on non-control Out endpoint  * @param  pdev: device instance  * @param  epnum: endpoint number  * @retval status  */static uint8_t  usbd_cdc_DataOut (void *pdev, uint8_t epnum){        uint16_t USB_Rx_Cnt;    /* Get the received data buffer and update the counter */  USB_Rx_Cnt = ((USB_OTG_CORE_HANDLE*)pdev)->dev.out_ep[epnum].xfer_count;    /* USB data will be immediately processed, this allow next USB traffic being      NAKed till the end of the application Xfer */  APP_FOPS.pIf_DataRx(USB_Rx_Buffer, USB_Rx_Cnt);    /* Prepare Out endpoint to receive next packet */  DCD_EP_PrepareRx(pdev,                   CDC_OUT_EP,                   (uint8_t*)(USB_Rx_Buffer),                   CDC_DATA_OUT_PACKET_SIZE);  return USBD_OK;}the APP_FOPS.pIf_DataRx(USB_Rx_Buffer, USB_Rx_Cnt); command passes it to your defined handler which is configured with a define in your usbd_conf.h file#define APP_FOPS                        VCP_fopsHopefully this helps enough.