STM32 USB Host Library 学习笔记 (1) USB_OTG_ReadPacket() USB_ReadPacket()

/**
* @brief  USB_OTG_ReadPacket : Reads a packet from the Rx FIFO
* @param  pdev : Selected device
* @param  dest : Destination Pointer
* @param  bytes : No. of bytes
* @retval None
*/
void *USB_OTG_ReadPacket(USB_OTG_CORE_HANDLE *pdev, 
                         uint8_t *dest, 
                         uint16_t len)
{
  uint32_t i=0;
  //uint32_t count32b = (len + 3) / 4;
  uint32_t count32b = (len) / 4;
  uint32_t count8b = (len) & 3;
  
  __IO uint32_t *fifo = pdev->regs.DFIFO[0];
  
  for ( i = 0; i < count32b; i++, dest += 4 )
  {
    *(__packed uint32_t *)dest = USB_OTG_READ_REG32(fifo);
    
  }
  
25   if ( count8b )
26   {
27     count32b = USB_OTG_READ_REG32(fifo);
28     while ( count8b > 0 )
29     {
30       *dest = count32b;
31       count32b >>= 8;
32       dest++;
33       count8b--;      
34     }
35   }

  return ((void *)dest);
}

/** @file stm32f4xx_ll_usb.c
  * @author MCD Application Team
  * @version V1.1.0
  * @date 19-June-2014
  * @brief USB Low Layer HAL module driver.
  */

/**
  * @brief  USB_ReadPacket : read a packet from the Tx FIFO associated 
  *         with the EP/channel
  * @param  USBx : Selected device  
  * @param  src : source pointer
  * @param  ch_ep_num : endpoint or host channel number
  * @param  len : Noumber of bytes to read
  * @param  dma: USB dma enabled or disabled 
  *          This parameter can be one of the these values:
  *           0 : DMA feature not used 
  *           1 : DMA feature used  
  * @retval pointer to desctination buffer
  */
void *USB_ReadPacket(USB_OTG_GlobalTypeDef *USBx, uint8_t *dest, uint16_t len)
{
  uint32_t i=0;
  uint32_t count32b = (len + 3) / 4;
  
  for ( i = 0; i < count32b; i++, dest += 4 )
  {
    *(__packed uint32_t *)dest = USBx_DFIFO(0); // dest buffer overflow if (len != n*4)    
  }
  return ((void *)dest);
}