本帖最后由 guanjilai 于 2016-9-11 23:43 编辑

这是HAL中三种回调函数之一HAL_PPP_MspInit()/_DeInit()，由HAL_PPP_Init()调用，api函数用来执行外设系统级的初始化（GPIOs，clock，DMA，interrupt）；在../Src/stm32f4xx_hal_msp.c中重写.
比如uart初始化时设置更底层的GPIOs，clock，DMA，interrupt,下面用uart来说明它是如何工作的
//在stm32f4xx_hal_uart.c定义，用__weak 关键字表示废弃函数定义，在其他地方重写
__weak void HAL_UART_MspInit(UART_HandleTypeDef *huart)
{
   /* Prevent unused argument(s) compilation warning */
  UNUSED(huart);
  /* NOTE: This function Should not be modified, when the callback is needed,
           the HAL_UART_MspInit could be implemented in the user file
   */
}
//在stm32f4xx_hal_uart.c调用
HAL_StatusTypeDef HAL_UART_Init(UART_HandleTypeDef *huart)
{
  /* Check the UART handle allocation */
  if(huart == NULL)
  {
    return HAL_ERROR;
  }

  /* Check the parameters */
  if(huart->Init.HwFlowCtl != UART_HWCONTROL_NONE)
  {
    /* The hardware flow control is available only for USART1, USART2, USART3 and USART6 */
    assert_param(IS_UART_HWFLOW_INSTANCE(huart->Instance));
    assert_param(IS_UART_HARDWARE_FLOW_CONTROL(huart->Init.HwFlowCtl));
  }
  else
  {
    assert_param(IS_UART_INSTANCE(huart->Instance));
  }
  assert_param(IS_UART_WORD_LENGTH(huart->Init.WordLength));
  assert_param(IS_UART_OVERSAMPLING(huart->Init.OverSampling));
  
  if(huart->gState == HAL_UART_STATE_RESET)
  {  
    /* Allocate lock resource and initialize it */
    huart->Lock = HAL_UNLOCKED;
    /* Init the low level hardware */
    HAL_UART_MspInit(huart);//此处调用
  }

  huart->gState = HAL_UART_STATE_BUSY;

  /* Disable the peripheral */
  __HAL_UART_DISABLE(huart);
  
  /* Set the UART Communication parameters */
  UART_SetConfig(huart);
  
  /* In asynchronous mode, the following bits must be kept cleared:
     - LINEN and CLKEN bits in the USART_CR2 register,
     - SCEN, HDSEL and IREN  bits in the USART_CR3 register.*/
  CLEAR_BIT(huart->Instance->CR2, (USART_CR2_LINEN | USART_CR2_CLKEN));
  CLEAR_BIT(huart->Instance->CR3, (USART_CR3_SCEN | USART_CR3_HDSEL | USART_CR3_IREN));
  
  /* Enable the peripheral */
  __HAL_UART_ENABLE(huart);
  
  /* Initialize the UART state */
  huart->ErrorCode = HAL_UART_ERROR_NONE;
  huart->gState= HAL_UART_STATE_READY;
  huart->RxState= HAL_UART_STATE_READY;
  
  return HAL_OK;
}

下面的stm32f4xx_hal_msp.c重写
void HAL_UART_MspInit(UART_HandleTypeDef *huart)
{  
  GPIO_InitTypeDef  GPIO_InitStruct;
  
  /*##-1- Enable peripherals and GPIO Clocks #################################*/
  /* Enable GPIO TX/RX clock */
  USARTx_TX_GPIO_CLK_ENABLE();
  USARTx_RX_GPIO_CLK_ENABLE();
  /* Enable USART1 clock */
  USARTx_CLK_ENABLE();
  
  /*##-2- Configure peripheral GPIO ##########################################*/  
  /* UART TX GPIO pin configuration  */
  GPIO_InitStruct.Pin       = USARTx_TX_PIN;
  GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull      = GPIO_NOPULL;
  GPIO_InitStruct.Speed     = GPIO_SPEED_FAST;
  GPIO_InitStruct.Alternate = USARTx_TX_AF;
  
  HAL_GPIO_Init(USARTx_TX_GPIO_PORT, &GPIO_InitStruct);
   
  /* UART RX GPIO pin configuration  */
  GPIO_InitStruct.Pin = USARTx_RX_PIN;
  GPIO_InitStruct.Alternate = USARTx_RX_AF;
   
  HAL_GPIO_Init(USARTx_RX_GPIO_PORT, &GPIO_InitStruct);
   
  /*##-3- Configure the NVIC for UART ########################################*/
  /* NVIC for USART1 */
  HAL_NVIC_SetPriority(USARTx_IRQn, 0, 1);
  HAL_NVIC_EnableIRQ(USARTx_IRQn);
}这样我们初始化时只要针对实例中变动的部分写出来就可以了，比如uart，我们只关注pin，中断就可以了