Thank you for your answer. I will try testing DTR. Also it sounds like you suggest using a timeout when sending data.
I send data this way:
while(CDC_Transmit_HS(array, size) == USBD_BUSY) ;
but I only want to do this if there is a connection. I can add code to break out of the loop if it times out,
but will I know that no bytes have been transferred in that case? It is important for my application not
to duplicate data.
I have found something that nearly works. I modified USBD_LL_DataInStage() to set a flag that tells me
if the remote host is connected, but it only sets the flag after I try to send. Here is the code, with my additions
marked with
//!!!
and placed at the left margin so it is clear what I added:
//!!!
uint8_t Connected = 0;
/**
* @brief USBD_DataInStage
* Handle data in stage
* @param pdev: device instance
* @param epnum: endpoint index
* @retval status
*/
USBD_StatusTypeDef USBD_LL_DataInStage(USBD_HandleTypeDef *pdev, uint8_t epnum,
uint8_t *pdata)
{
USBD_EndpointTypeDef *pep;
if(epnum == 0U)
{
pep = &pdev->ep_in[0];
if ( pdev->ep0_state == USBD_EP0_DATA_IN)
{
if(pep->rem_length > pep->maxpacket)
{
pep->rem_length -= pep->maxpacket;
USBD_CtlContinueSendData (pdev, pdata, (uint16_t)pep->rem_length);
/* Prepare endpoint for premature end of transfer */
USBD_LL_PrepareReceive (pdev, 0U, NULL, 0U);
}
else
{ /* last packet is MPS multiple, so send ZLP packet */
if((pep->total_length % pep->maxpacket == 0U) &&
(pep->total_length >= pep->maxpacket) &&
(pep->total_length < pdev->ep0_data_len))
{
USBD_CtlContinueSendData(pdev, NULL, 0U);
pdev->ep0_data_len = 0U;
/* Prepare endpoint for premature end of transfer */
USBD_LL_PrepareReceive (pdev, 0U, NULL, 0U);
}
else
{
if((pdev->pClass->EP0_TxSent != NULL)&&
(pdev->dev_state == USBD_STATE_CONFIGURED))
{
pdev->pClass->EP0_TxSent(pdev);
}
USBD_LL_StallEP(pdev, 0x80U);
USBD_CtlReceiveStatus(pdev);
}
}
}
else
{
if ((pdev->ep0_state == USBD_EP0_STATUS_IN) ||
(pdev->ep0_state == USBD_EP0_IDLE))
{
USBD_LL_StallEP(pdev, 0x80U);
//!!!
Connected = 0;
}
}
if (pdev->dev_test_mode == 1U)
{
USBD_RunTestMode(pdev);
pdev->dev_test_mode = 0U;
}
}
else if((pdev->pClass->DataIn != NULL) &&
(pdev->dev_state == USBD_STATE_CONFIGURED))
{
pdev->pClass->DataIn(pdev, epnum);
//!!!
Connected = 1;
}
else
{
/* should never be in this condition */
return USBD_FAIL;
}
return USBD_OK;
}
I feel like this is close to what I need. Any suggestions on how to make the code set or clear a flag
on read instead of write? Or, can I write a null packet? Is it OK to do something like this:
CDC_Transmit_HS(NULL, 0);
