STM32F USB interrupt analysis

Sometimes I always wonder, what is the best way to learn? Just like learning USB, is it enough to just learn how to apply it, or do I have to go deep into the protocol content and the underlying driver? I often tell others that I know something, but in fact I only know a little bit, and I only know some applications to fool others. So I always comfort myself: I just need to make some applications!!!

The following introduces the two files usb_endp.c and usb_istr.c of the STM32 USB project.

First is usb_endp.c. This file is very simple. It just defines several endpoint input and output functions. My project only has it.

uint8_t USB_Receive_Buffer[REPORT_COUNT]; //Endpoint receives data buffer REPORT_COUNT=64

uint8_t USB_Send_Buffer[REPORT_COUNT]; //Endpoint sends data buffer

volatile uint8_t USB_Received_Flag=0; //USB received data flag

/****************************************************** ****************************

* Function Name: EP1_IN_Callback.

* Description: Endpoint 1 input callback function

* Input : None.

* Output : None.

* Return : None.

*************************************************** *******************************/

void EP1_IN_Callback(void)

{

}

/****************************************************** ****************************

* Function Name: EP1_OUT_Callback.

* Description: Endpoint 1 output callback function

* Input : None.

* Output : None.

* Return : None.

*************************************************** *******************************/

void EP1_OUT_Callback(void)

{

        USB_SIL_Read(EP1_OUT,USB_Receive_Buffer); //Read the data of output endpoint

        USB_Received_Flag=1; //Flag of received data

}

/****************************************************** ****************************

* Function Name: EP2_IN_Callback.

* Description : Endpoint input callback function.

* Input : None.

* Output : None.

* Return : None.

*************************************************** *******************************/

void EP2_IN_Callback(void)

{

}

Next, we will divide usb_istr.c. This c file mainly registers some endpoint response functions, such as the endpoint input and output callback function above, and the interrupt processing of the ISTR interrupt status register, as follows:

__IO uint16_t wIstr; /* Used to save the value read from the ISRT register*/

__IO uint8_t bIntPackSOF = 0; /* Number of start of frame packets (SOFs) received between two consecutive data packets */

/*Define an array of function pointers pointing to pointers. The function pointers point to 7 endpoint input service programs respectively*/

void (*pEpInt_IN[7])(void) =

  {

    EP1_IN_Callback,

    EP2_IN_Callback,

    EP3_IN_Callback,

    EP4_IN_Callback,

    EP5_IN_Callback,

    EP6_IN_Callback,

    EP7_IN_Callback,

  };

/*Define an array of function pointers pointing to pointers. The function pointers point to 7 endpoint output service programs respectively*/

void (*pEpInt_OUT[7])(void) =

  {

    EP1_OUT_Callback,

    EP2_OUT_Callback,

    EP3_OUT_Callback,

    EP4_OUT_Callback,

    EP5_OUT_Callback,

    EP6_OUT_Callback,

    EP7_OUT_Callback,

  };

#ifndef STM32F10X_CL

/****************************************************** ****************************

* Function Name : USB_Istr

* Description: ISTR interrupt event interrupt service routine

* Input : None.

* Output : None.

* Return : None.

*************************************************** *******************************/

void USB_Istr(void)

{

  wIstr = _GetISTR(); //Read the value of the interrupt status register (ISTR)

#if (IMR_MSK & ISTR_CTR) //Correct transmission interrupt CTR flag

  if (wIstr & ISTR_CTR &wInterrupt_Mask)

  {

    /* servicing of the endpoint correct transfer interrupt */

    /* clear of the CTR flag into the sub */

    CTR_LP(); //Call the correct transmission interrupt service routine

#ifdef CTR_CALLBACK

    CTR_Callback(); //When CTR_CALLBACK is defined, CTR_Callback is called, like a hook function, to do something when a CRT interrupt occurs

#endif

  }

#endif 

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_RESET) //Reset (RESET) interrupt flag

  if (wIstr & ISTR_RESET & wInterrupt_Mask) //The interrupt flag read is the RESET interrupt flag, and the RESET interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_RESET); //Clear RESET interrupt flag

    Device_Property.Reset(); //Call the reset function

#ifdef RESET_CALLBACK

    RESET_CALLBACK(); //When RESET_CALLBACK is defined, call RESET_CALLBACK, like a hook function, to do something when a RESET interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_DOVR) //Packet buffer overflow (DOVR) interrupt flag

  if (wIstr & ISTR_DOVR & wInterrupt_Mask) //The interrupt flag read is the DOVR interrupt flag, and the DOVR interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_DOVR); //Clear DOVR interrupt flag

#ifdef DOVR_CALLBACK

    DOVR_Callback(); //When DOVR_CALLBACK is defined, DOVR_Callback is called, just like a hook function, to do something when a DOVR interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_ERR) //Error (ERR) interrupt flag

  if (wIstr & ISTR_ERR & wInterrupt_Mask) //The interrupt flag read is the ERR interrupt flag, and the ERR interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_ERR); //Clear ERR interrupt flag

#ifdef ERR_CALLBACK

    ERR_Callback(); //When ERR_CALLBACK is defined, ERR_Callback is called, like a hook function, to do something when an ERR interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_WKUP) //Wake-up (WKUP) interrupt flag

  if (wIstr & ISTR_WKUP & wInterrupt_Mask) //The interrupt flag read is the WKUP interrupt flag, and the WKUP interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_WKUP); //Clear ERR interrupt flag

    Resume(RESUME_EXTERNAL); //Call the wake-up function

#ifdef WKUP_CALLBACK

    WKUP_Callback(); //When WKUP_CALLBACK is defined, WKUP_Callback is called, just like a hook function, to do something when a WKUP interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_SUSP) //Suspend (SUSP) interrupt flag

  if (wIstr & ISTR_SUSP & wInterrupt_Mask) //The interrupt flag read is the SUSP interrupt flag, and the SUSP interrupt is enabled

  {

    /* check if SUSPEND is possible */

    if (fSuspendEnabled) // Check if it can be suspended

    {

      Suspend(); //If it is possible to suspend, call the suspend function

    }

    else

    {

      /* if not possible then resume after xx ms */

      Resume(RESUME_LATER); //If suspend is not allowed, resume after xx ms

    }

    /* clear of the ISTR bit must be done after setting ofCNTR_FSUSP */

    _SetISTR((uint16_t)CLR_SUSP); //Clear SUSP interrupt flag

#ifdef SUSP_CALLBACK

    SUSP_Callback(); //When SUSP_CALLBACK is defined, SUSP_Callback is called, just like a hook function, to do something when a SUSP interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_SOF) //Start of frame (SOF) interrupt flag

  if (wIstr & ISTR_SOF & wInterrupt_Mask) //The interrupt flag read is the SOF interrupt flag, and the SOF interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_SOF); //Clear SOF interrupt flag

    bIntPackSOF++; //Count the total number of SOFs received

#ifdef SOF_CALLBACK

    SOF_Callback(); //When SOF_CALLBACK is defined, SOF_Callback is called, like a hook function, to do something when a SOF interrupt occurs

#endif

  }

#endif

  /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*-*-*-*-*-*-*-*/

#if (IMR_MSK & ISTR_ESOF) //Expected frame start (ESOF) interrupt flag, when the expected SOF frame start is not received, the interrupt is triggered

  if (wIstr & ISTR_ESOF & wInterrupt_Mask) //The interrupt flag read is the SOF interrupt flag, and the ESOF interrupt is enabled

  {

    _SetISTR((uint16_t)CLR_ESOF); //Clear ESOF interrupt flag

    /* resume handling timing is made with ESOFs */ 

        /* request without change of the machine state */

    Resume(RESUME_ESOF); //Resume ESOF processing time

#ifdef ESOF_CALLBACK

    ESOF_Callback(); //When ESOF_CALLBACK is defined, ESOF_Callback is called like a hook function to do something when an ESOF interrupt occurs

#endif

  }

#endif

} /* USB_Istr */