Electronic – STM32 USB: detecting connection and disconnection

stm32stm32f4usb

Using STM32F4 USB Mass Storage Controller example in Device Mode, how do you detect connections and disconnections with a host controller?

I tried polling the VBUS pin state yet it could be high from a wall adapter or high without any communication with the host.

Is there a register to check? I noticed DSTS (status I guess?) in the USB library structs but couldn't find its documentation nor any useful comments in the code.

Best Answer

You could detect the connection and disconnection from this file:

usbd_core.c

and the API for it is this

USBD_StatusTypeDef USBD_LL_DevConnected(USBD_HandleTypeDef  *pdev)
USBD_StatusTypeDef USBD_LL_DevDisconnected(USBD_HandleTypeDef  *pdev)

I am not sure about USB Mass Storage Class but in the CDC class, the 2 APIs above detect the USB connection and disconnection, maybe this helps

Things to note:

Connection > when the physical USB cable is plugged into the USB port
Disconnection > when the physical USB cable is unplugged from the USB port

I used STMCubeMX to generate the USB CDC class.

Related Solutions

Electronic – Throttling data from USB serial connection on STM32 microcontroller (flow control)

I appear to have got this working:

void EP3_OUT_Callback(void) {
 ...
  //SetEPRxValid(ENDP3); //<-- Commented out
  SetEPRxStatus(ENDP3, Do_I_Have_Room_For_More_Data() ? EP_RX_VALID : EP_RX_NAK); //<-- Added this
}

void SOF_Callback(void) {
  if(bDeviceState == CONFIGURED) {
    SetEPRxStatus(ENDP3, Do_I_Have_Room_For_More_Data() ? EP_RX_VALID : EP_RX_NAK); //<-- Added this
    ...
    // Original TX code here
  }
}

What's happening is after getting data, and in the Start of Frame callback (every 1ms), I set whether the endpoint is accepting data.

Note: The docs never seem to say just how much data USB_SIL_Read will read - potentially leading to a buffer overrun. However I believe the maximum is what is in VIRTUAL_COM_PORT_DATA_SIZE - and this seems to work great for me.

This would appear to work - however I have no idea if it is the 'right' way of doing it. Please let me know if it's wrong and I'll update it!

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).

Best Answer

Related Solutions

Electronic – Throttling data from USB serial connection on STM32 microcontroller (flow control)

Electronic – STM32 Virtual COM port baud rate

Related Topic