STM32F4 VCP transmit/receive data

microcontrollerstm32stm32cubemxstm32f4usb

I'm using STM32 VCP firmware on STM32F4 discovery. I generated the code with CubeMX and I could successfully integrate it into my Eclipse project. After calling the initialisation functions, the device appears on my PC as virtual com port, so the drivers are fine.

But where can I find the functions in the library, which do the trasmitting and receiving data on the STM32 device? I know this is a very basic question, but I'm looking for them for a long time.

Best Answer

In my VCP project:

file: usbd_cdc_vcp.c

uint16_t VCP_DataTx (uint8_t* Buf, uint32_t Len); <-You call it to send data from STM to PC

and

uint16_t VCP_DataRx (uint8_t* Buf, uint32_t Len) {
  // Called when data from PC to STM is available.  

  // YOUR CODE IS HERE

  return USBD_OK
}

Related Solutions

Electronic – STM32 Virtual COM port baud rate

The CDC_Transmit_FS implementation is buggy (at least in the version I am looking at):

uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len)
{
  uint8_t result = USBD_OK;
  /* USER CODE BEGIN 8 */
  USBD_CDC_SetTxBuffer(hUsbDevice_0, UserTxBufferFS, Len);  
  result = USBD_CDC_TransmitPacket(hUsbDevice_0);
  /* USER CODE END 8 */
  return result;
}

As you can see the Buff parameter is never used in the function. You might try modifying the function, by copying the Buff into UserTxBufferFS (using memcpy or whatever).

Electronic – STM32 VCP – Receive data from PC

I found the answer for my own question. There is a well documentated example on the following webpage: http://visualgdb.com/tutorials/arm/stm32/usb/

First of all, I had to complete the generated code in static int8_t CDC_Receive_FS (char* Buf, uint32_t *Len) as it is written in the source above.

After that I had to create and implement the int VCP_read(void *pBuffer, int size) function, as it is written in the above mentioned source.

The key point was, that I had to call periodically the int VCP_read(void *pBuffer, int size) function, to read out from the buffer the received data. If I don't call this function, the PC can't write next time the COM port.

Best Answer

Related Solutions

Electronic – STM32 Virtual COM port baud rate

Electronic – STM32 VCP – Receive data from PC

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