CubeMx中HAL库函数的调用不同于库函数调用，在学习CubeMx串口通信时，不理解HAL库中的回调函数是怎么被调用的，于是查看每个的定义，参考其他人写的博客，总算弄明白了HAL库中断调用与库函数不同之处。写下这篇博客一是加深自己的理解，二是希望对不理解HAL库中回调函数调用机制的朋友有所帮助。
工程代码参考：【STM32】-CubeMX-HAL库-UART-串口通信-STM32F103C8T6-收发测试
在库函数中，UART串口发生中断时，我们直接将业务代码写在void USART1_IRQHandler(void)中，如下图：
void USART1_IRQHandler(void) //串口1中断服务程序{u8 Res;if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) //接收中断(接收到的数据必须是0x0d 0x0a结尾){Res =USART_ReceiveData(USART1);//读取接收到的数据if((USART_RX_STA&0x8000)==0)//接收未完成{if(USART_RX_STA&0x4000)//接收到了0x0d{if(Res!=0x0a)USART_RX_STA=0;//接收错误,重新开始else USART_RX_STA|=0x8000;//接收完成了 }else //还没收到0X0D{if(Res==0x0d)USART_RX_STA|=0x4000;else{USART_RX_BUF[USART_RX_STA&0X3FFF]=Res ;USART_RX_STA++;if(USART_RX_STA>(USART_REC_LEN-1))USART_RX_STA=0;//接收数据错误,重新开始接收 } }} } } 对于CubeMX生成的代码，USART1_IRQHandler(void)函数为了提高中断效率采用了回调机制。（业务代码可以等中断关闭了再去处理，这样中断处理不会占用太多时间影响程序的执行效率）
USART1_IRQHandler(void)函数中只调用了HAL_UART_IRQHandler(&huart1)（可以在STM32f1xx_it.c中找到），参数为uart1的句柄huart1，句柄可以理解为通过huart1访问到uart1的各种寄存器和数据类型，不理解的话，可以去看UART_HandleTypeDef结构体的定义。
在HAL_UART_IRQHandler(UART_HandleTypeDef *huart)函数内又调用了UART_Receive_IT(huart);（回调函数在这个函数中被调用）看注释理解该函数的作用
static HAL_StatusTypeDef UART_Receive_IT(UART_HandleTypeDef *huart){ //用这个指针指向我们用于接收数据的变量或数组，在收发测试例程中定义的是char Res uint8_t *pdata8bits; uint16_t *pdata16bits; /* Check that a Rx process is ongoing */ if (huart->RxState == HAL_UART_STATE_BUSY_RX) { if ((huart->Init.WordLength == UART_WORDLENGTH_9B) && (huart->Init.Parity == UART_PARITY_NONE)) { pdata8bits = NULL; pdata16bits = (uint16_t *) huart->pRxBuffPtr;//指向Res,相当于pdata16bits=&Res //具体原因参考HAL_UART_Receive_IT(&huart1, &Res, 1); *pdata16bits = (uint16_t)(huart->Instance->DR & (uint16_t)0x01FF); huart->pRxBuffPtr += 2U; } else { pdata8bits = (uint8_t *) huart->pRxBuffPtr;//指向Res,相当于pdata8bits=&Res pdata16bits = NULL; if ((huart->Init.WordLength == UART_WORDLENGTH_9B) || ((huart->Init.WordLength == UART_WORDLENGTH_8B) && (huart->Init.Parity == UART_PARITY_NONE))) { //指针操作 相当于Res= (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF); *pdata8bits = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF); } else { //指针操作 相当于Res= (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF); *pdata8bits = (uint8_t)(huart->Instance->DR & (uint8_t)0x007F); } huart->pRxBuffPtr += 1U; } if (--huart->RxXferCount == 0U)//关闭中断，准备回调，对串口接收到的数据保存 { /* Disable the UART Data Register not empty Interrupt */ __HAL_UART_DISABLE_IT(huart, UART_IT_RXNE); /* Disable the UART Parity Error Interrupt */ __HAL_UART_DISABLE_IT(huart, UART_IT_PE); /* Disable the UART Error Interrupt: (Frame error, noise error, overrun error) */ __HAL_UART_DISABLE_IT(huart, UART_IT_ERR); /* Rx process is completed, restore huart->RxState to Ready */ huart->RxState = HAL_UART_STATE_READY; /* Check current reception Mode : If Reception till IDLE event has been selected : */ if (huart->ReceptionType == HAL_UART_RECEPTION_TOIDLE) { /* Set reception type to Standard */ huart->ReceptionType = HAL_UART_RECEPTION_STANDARD; /* Disable IDLE interrupt */ CLEAR_BIT(huart->Instance->CR1, USART_CR1_IDLEIE); /* Check if IDLE flag is set */ if (__HAL_UART_GET_FLAG(huart, UART_FLAG_IDLE)) { /* Clear IDLE flag in ISR */ __HAL_UART_CLEAR_IDLEFLAG(huart); }#if (USE_HAL_UART_REGISTER_CALLBACKS == 1) /*Call registered Rx Event callback*/ huart->RxEventCallback(huart, huart->RxXferSize);#else /*Call legacy weak Rx Event callback*/ HAL_UARTEx_RxEventCallback(huart, huart->RxXferSize);#endif } else { /* Standard reception API called */#if (USE_HAL_UART_REGISTER_CALLBACKS == 1) /*Call registered Rx complete callback*/ huart->RxCpltCallback(huart);#else /*Call legacy weak Rx complete callback*/ HAL_UART_RxCpltCallback(huart);//正常情况下会执行这一条语句 //我们可以自己定义这个函数内部的具体操作#endif /* USE_HAL_UART_REGISTER_CALLBACKS */ } return HAL_OK; } return HAL_OK; } else { return HAL_BUSY; }}表格中左右两边的操作为什么等价呢？
| pdata8bits = (uint8_t *) huart->pRxBuffPtr; | pdata8bits=&Res |
| *pdata8bits = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF); | Res= (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF); |
可以从UART_Start_Receive_IT函数中找到答案
（UART_Start_Receive_IT被main函数中的HAL_UART_Receive_IT调用）
//函数参数相当于（&huart1, &Res, 1）HAL_StatusTypeDef UART_Start_Receive_IT(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size){ //函数参数相当于（&huart1, &Res, 1） huart->pRxBuffPtr = pData;//pData==&Res //在UART_Receive_IT函数中 pdata8bits = (uint8_t *) huart->pRxBuffPtr; //pdata8bits=&Res，其他都是同理，如果不理解，需要回顾一下指针操作。 huart->RxXferSize = Size;//Size==1 huart->RxXferCount = Size; huart->ErrorCode = HAL_UART_ERROR_NONE; huart->RxState = HAL_UART_STATE_BUSY_RX; /* Process Unlocked */ __HAL_UNLOCK(huart); /* Enable the UART Parity Error Interrupt */ __HAL_UART_ENABLE_IT(huart, UART_IT_PE); /* Enable the UART Error Interrupt: (Frame error, noise error, overrun error) */ __HAL_UART_ENABLE_IT(huart, UART_IT_ERR); /* Enable the UART Data Register not empty Interrupt */ __HAL_UART_ENABLE_IT(huart, UART_IT_RXNE); return HAL_OK;}回调函数：
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)//自定义回调函数 在UART_Receive_IT()中调用{//判断是哪个串口触发的中断 huart1.Instance = USART1;定义在MX_USART1_UART_Init中if(huart==&huart1)//huart ->Instance == USART1两种判断条件等价{if((UART1_RX_STA & 0x8000)==0)//接收未完成&位运算符 &&短路与判断{if(UART1_RX_STA & 0x4000)//接收到 \r{if(Res==0x0a)//下一个必须是接收 \nUART1_RX_STA|=0x8000;elseUART1_RX_STA=0;}else //未接收到\r{if(Res==0x0d)//Receive \r{UART1_RX_STA|=0x4000;}else{UART1_RX_Buffer[UART1_RX_STA&0X3FFF]=Res;UART1_RX_STA++;if(UART1_RX_STA>UART1_REC_LEN-1) UART1_RX_STA=0;//如果接收数据大于200Byte 重新开始接收}}}HAL_UART_Receive_IT(&huart1, &Res, 1);//完成一次接受，再此开启中断}}如果我们自己没有定义回调函数的话，系统会调用自带的回调函数，函数类型为__weak，表示弱定义
如果用户自己定义了函数就优先调用用户定义的回调函数
__weak void HAL_UART_RxCpltCallback(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_RxCpltCallback could be implemented in the user file */}