先上一个采用串口直接传输的Demo；

此处的思路是完全采用HAL库来实现的，核心是运用HAL_UART_Transmit_IT和HAL_UART_Receive_IT两个函数来实现的，可以作为一个Demo来测试使用；

直接上代码，其串口的配置和上一章完全一致，因此忽略不计：

       思路大致是将aTxStartMessage字符串发送出去，接收一个总长度为15个字符的数据到aRxBuffer中，等待接收完毕；

       将接收到的aRxBuffer发送出去，等待发送完成，最后将aTxEndMessage发送出去；

uint8_t aTxStartMessage[] = "\r\n ****UART-Hyperterminal communication based on IT ****\r\n Enter 9 characters using keyboard :\r\n";uint8_t aTxEndMessage[] = "\r\n Example Finished\r\n";/* Buffer used for reception */uint8_t aRxBuffer[18];    while (1)  {    if(HAL_UART_Transmit_IT(&huart2, (uint8_t*)aTxStartMessage, sizeof(aTxStartMessage)) != HAL_OK)    {        while(1);    }    if(HAL_UART_Receive_IT(&huart2, (uint8_t*)aRxBuffer, 15) != HAL_OK)    {        while(1);    }    while(HAL_UART_GetState(&huart2) != HAL_UART_STATE_READY);    if(HAL_UART_Transmit_IT(&huart2, (uint8_t*)aRxBuffer, 15) != HAL_OK)    {        while(1);    }    while(HAL_UART_GetState(&huart2) != HAL_UART_STATE_READY);    if(HAL_UART_Transmit_IT(&huart2, (uint8_t*)aTxEndMessage, sizeof(aTxEndMessage)) != HAL_OK)    {        while(1);    }    while(HAL_UART_GetState(&huart2) != HAL_UART_STATE_READY);  }

 

 

接下来是也是一个Demo，采用HAL库来实现串口收发中断，思路和C一个一个接收字符然后发送出去是相似的，只不过是采用串口IT中断来实现；

　　串口的配置不变，因此在此忽略不计；

uint8_t aRxBuffer;int main(void){  HAL_Init();  SystemClock_Config();  MX_GPIO_Init();  MX_USART2_UART_Init();    HAL_UART_Receive_IT(&huart3, &aRxBuffer, 1);    while (1)  {}}void USART2_IRQHandler(void){  HAL_UART_IRQHandler(&huart2);}void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandler){    HAL_UART_Transmit(&huart3, &aRxBuffer, 1, 0);    HAL_UART_Receive_IT(&huart3, &aRxBuffer, 1);}

 

 

简要分析以下这个程序的思路：

       开头采用HAL_UART_Receive_IT()这个函数和目的不是为了接收数据，而是通过里面的配置开启中断，核心在SET_BIT()这两句话中（开启EIE、PEIE和RXNEIE这三个中断）；

HAL_StatusTypeDef HAL_UART_Receive_IT(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size){  /* Check that a Rx process is not already ongoing */  if(huart->RxState == HAL_UART_STATE_READY)  {    if((pData == NULL ) || (Size == 0U))    {      return HAL_ERROR;    }    /* In case of 9bits/No Parity transfer, pData buffer provided as input paramter        should be aligned on a u16 frontier, as data to be received from RDR will be        handled through a u16 cast. */    if ((huart->Init.WordLength == UART_WORDLENGTH_9B) && (huart->Init.Parity == UART_PARITY_NONE))    {      if((((uint32_t)pData)&1U) != 0U)      {        return  HAL_ERROR;      }    }    /* Process Locked */    __HAL_LOCK(huart);    huart->pRxBuffPtr = pData;    huart->RxXferSize = Size;    huart->RxXferCount = Size;    /* Computation of UART mask to apply to RDR register */    UART_MASK_COMPUTATION(huart);    huart->ErrorCode = HAL_UART_ERROR_NONE;    huart->RxState = HAL_UART_STATE_BUSY_RX;    /* Process Unlocked */    __HAL_UNLOCK(huart);    /* Enable the UART Error Interrupt: (Frame error, noise error, overrun error) */    SET_BIT(huart->Instance->CR3, USART_CR3_EIE);    /* Enable the UART Parity Error and Data Register not empty Interrupts */    SET_BIT(huart->Instance->CR1, USART_CR1_PEIE | USART_CR1_RXNEIE);    return HAL_OK;  }  else  {    return HAL_BUSY;  }}

 

 

接收数据的过程可以从中断中了解：

       当接收到数据后判断ISR寄存器中RXNE中断标志是否置位和CR1寄存器中RXNE中断使能是否开启，然后进入到接收处理函数UART_Receive_IT()中；

       在UART_Receive_IT()中，关闭EIE、PEIE和RXNE中断，同时调用回调函数HAL_UART_RxCpltCallback()；

void USART2_IRQHandler(void){  HAL_UART_IRQHandler(&huart2);}void HAL_UART_IRQHandler(UART_HandleTypeDef *huart){  /* If some errors occur */  cr3its = READ_REG(huart->Instance->CR3);  if(   (errorflags != RESET)     && (   ((cr3its & USART_CR3_EIE) != RESET)         || ((cr1its & (USART_CR1_RXNEIE | USART_CR1_PEIE)) != RESET)) )  {        /* Call UART Error Call back function if need be --------------------------*/    if(huart->ErrorCode != HAL_UART_ERROR_NONE)    {      /* UART in mode Receiver ---------------------------------------------------*/      if(((isrflags & USART_ISR_RXNE) != RESET) && ((cr1its & USART_CR1_RXNEIE) != RESET))      {        UART_Receive_IT(huart);      }    }    return;  } /* End if some error occurs */}HAL_StatusTypeDef UART_Receive_IT(UART_HandleTypeDef *huart){  /* Check that a Rx process is ongoing */  if(huart->RxState == HAL_UART_STATE_BUSY_RX)  {    if(--huart->RxXferCount == 0U)    {      /* Disable the UART Parity Error Interrupt and RXNE interrupt*/      CLEAR_BIT(huart->Instance->CR1, (USART_CR1_RXNEIE | USART_CR1_PEIE));      /* Disable the UART Error Interrupt: (Frame error, noise error, overrun error) */      CLEAR_BIT(huart->Instance->CR3, USART_CR3_EIE);      /* Rx process is completed, restore huart->RxState to Ready */      huart->RxState = HAL_UART_STATE_READY;      HAL_UART_RxCpltCallback(huart);      return HAL_OK;    }  }}

 

 

在主函数中执行重写的回调函数：

       将接收到的一个字符发送出去，同时开启接收中断准备接收下一个字符；

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandler){    HAL_UART_Transmit(&huart3, &aRxBuffer, 1, 0);    HAL_UART_Receive_IT(&huart3, &aRxBuffer, 1);}

 

 

其实现的功能可以和以下C语言实现的相似：

int c;while((c = getchar()) != EOF){    putchar(c);}