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J
JVERN.18
Associate III
January 7, 2019
Question

Bug in STM32CubeMx code generation for CDC Host if length > 64 ?

  • January 7, 2019
  • 1 reply
  • 693 views

Hello,

STM32CubeMx for the CDC Host mode, there seems to be a problem in the "static void CDC_ProcessReception (USBH_HandleTypeDef * phost)" function of the "usbh_cdc.c" file if we use the "USBH_CDC_Receive" function (USBH_HandleTypeDef * phost, uint8_t * pbuff , uint32_t length) "with length> wMaxPacketSize (here 64).

Indeed, in the line 36 :

/**
* @brief This function responsible for reception of data from the device
* @param pdev: Selected device
* @retval None
*/
 
static void CDC_ProcessReception(USBH_HandleTypeDef *phost)
{
 CDC_HandleTypeDef *CDC_Handle = (CDC_HandleTypeDef*) phost->pActiveClass->pData;
 USBH_URBStateTypeDef URB_Status = USBH_URB_IDLE;
 uint32_t length;
 
 switch(CDC_Handle->data_rx_state)
 {
 
 case CDC_RECEIVE_DATA:
 
 USBH_BulkReceiveData (phost,
 CDC_Handle->pRxData,
 CDC_Handle->DataItf.InEpSize,
 CDC_Handle->DataItf.InPipe);
 
 CDC_Handle->data_rx_state = CDC_RECEIVE_DATA_WAIT;
 
 break;
 
 case CDC_RECEIVE_DATA_WAIT:
 
 URB_Status = USBH_LL_GetURBState(phost, CDC_Handle->DataItf.InPipe);
 
 /*Check the status done for reception*/
 if(URB_Status == USBH_URB_DONE)
 {
 length = USBH_LL_GetLastXferSize(phost, CDC_Handle->DataItf.InPipe);
 
 if(((CDC_Handle->RxDataLength - length) > 0U) && (length > CDC_Handle->DataItf.InEpSize))
 {
 CDC_Handle->RxDataLength -= length ;
 CDC_Handle->pRxData += length;
 CDC_Handle->data_rx_state = CDC_RECEIVE_DATA;
 }
 else
 {
 CDC_Handle->data_rx_state = CDC_IDLE;
 USBH_CDC_ReceiveCallback(phost);
 }
 
#if (USBH_USE_OS == 1U)
 phost->os_msg = (uint32_t)USBH_CLASS_EVENT;
#if (osCMSIS < 0x20000U)
 (void)osMessagePut(phost->os_event, phost->os_msg, 0U);
#else
 (void)osMessageQueuePut(phost->os_event, &phost->os_msg, 0U, NULL);
#endif
#endif
 }
 break;
 
 default:
 break;
 }
}

We see that the test "(length> CDC_Handle-> DataItf.InEpSize)" is never true because "length" is always less than or equal to (actually equal to) "InEpSize" which is initialized with "wMaxPacketSize", here 64 .

It would probably be necessary to change the test for "... && (length == CDC_Handle-> DataItf.InEpSize))" or "... && (length> = CDC_Handle-> DataItf.InEpSize))"

This topic has been closed for replies.

1 reply

JMeye.2
JMeye.2
Associate II
October 21, 2020

Hey I just had a similar thought. Did you confirm this as a problem in the end?

Also I notice that USBH_BulkReceiveData uses CDC_Handle->DataItf.InEpSize as a size but with CDC_Handle->pRxData as buffer so would this require

USBH_CDC_Receive to be called with length a multiple of CDC_Handle->DataItf.InEpSize?

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