Posted on November 09, 2015 at 18:27I've been working on the Isoc incomplete issue... And got pretty good idea, which solved this problem. At the isoc incomplete interrupt, I mark the current pid (last bit of frame number). At the SOF interrupt, I test if current frame has the same parity, and when it's true, transmit the feedback endpoint data. This way is 100% working.
static uint8_t usbd_audio_IN_Incplt (void *pdev)
{
//This ISR is executed every time when IN token received with ''wrong'' PID. It's necessary
//to flush IN EP (feedback EP), get parity value from DSTS, and store this info for SOF handler.
//SOF handler should skip one frame with ''wrong'' PID and attempt a new transfer a frame later.
USB_OTG_DSTS_TypeDef FS_DSTS;
FS_DSTS.d32 = USB_OTG_READ_REG32(&(((USB_OTG_CORE_HANDLE*)pdev)->regs.DREGS->DSTS));
dpid=(FS_DSTS.b.soffn)&0x1;
if (flag)
{flag=0;
DCD_EP_Flush(pdev,AUDIO_IN_EP);
STM_EVAL_LEDToggle(LED4);
};
return USBD_OK;
}
static uint8_t usbd_audio_SOF (void *pdev)
{ uint8_t res;
static uint16_t n;
USB_OTG_DSTS_TypeDef FS_DSTS;
/* Check if there are available data in stream buffer.
In this function, a single variable (PlayFlag) is used to avoid software delays.
The play operation must be executed as soon as possible after the SOF detection. */
if (usbd_audio_AltSet==1)
{
if (PlayFlag)
{
gap=(IsocOutWrPtr-IsocOutRdPtr);
tmpxx=(DMA1_Stream7->NDTR);
if (gap<0) gap+=(AUDIO_OUT_PACKET * OUT_PACKET_NUM);
dgap=gap+tmpxx;
};
accum+=(TIM2->CCR1);
SOF_num++;
if (SOF_num==(1<<SOF_RATE))
{if (SOF_RATE>6)
{feedback_data+=accum>>(SOF_RATE-6);}
else
{feedback_data+=accum<<(6-SOF_RATE);};
feedback_data>>=1;
SOF_num=0;
accum=0;
}
if ((!flag))
{
FS_DSTS.d32 = USB_OTG_READ_REG32(&(((USB_OTG_CORE_HANDLE*)pdev)->regs.DREGS->DSTS));
if (((FS_DSTS.b.soffn)&0x1) == dpid)
{
DCD_EP_Tx (pdev, AUDIO_IN_EP, (uint8_t *) &feedback_data, 3);
flag=1;
};
};
}
return USBD_OK;
}
The code in IN handler is the same. This scheme detects right PID and always sends feedback data.
