usb_lld.c otg_txfifo_handler

    if(ep==1){
      dtxfsts = OTG->ie[ep].DTXFSTS&0x1ff;   //IN endpoint TxFIFO space available
      while( ((dtxfsts) > 0) &&
            (usbp->epc[ep]->in_state->txsize > usbp->epc[ep]->in_state->txcnt) )
      {

        n = usbp->epc[ep]->in_state->txsize - usbp->epc[ep]->in_state->txcnt;

        len = dtxfsts*4;

        if (len > usbp->epc[ep]->in_maxsize)
            len = usbp->epc[ep]->in_maxsize;
        if(len>=n)
        {
          /* Last packet */
          len=n;
          OTG->DIEPEMPMSK &= ~DIEPEMPMSK_INEPTXFEM(ep);
        }
        otg_fifo_write_from_buffer(ep,
                                   usbp->epc[ep]->in_state->mode.linear.txbuf,
                                   len);
        usbp->epc[ep]->in_state->mode.linear.txbuf += len;
        usbp->epc[ep]->in_state->txcnt += len;

        dtxfsts = OTG->ie[ep].DTXFSTS&0x1ff;
      }
    }