MX串口配置方法見：CubeIDE 利用自帶HAL庫 串口收發
一、代碼自動生成以後的項目及代碼結構：
main.c中，調用了串口初始化
串口初始化函數賦值了串口的參數
相當於底層的初始化，配置引腳、並開啓中斷。
至此串口1配置完畢
二、庫文件stm32f1xx_hal_uart.c內的祕密
2.1 初始化
1.usart.c中，MX_USART1_UART_Init 調用了庫的HAL_UART_Init，將結構體傳遞進該函數中
2.HAL_UART_Init幹了些什麼事？
if (huart->gState == HAL_UART_STATE_RESET)
{
huart->Lock = HAL_UNLOCKED;
HAL_UART_MspInit(huart);
}
huart->gState = HAL_UART_STATE_BUSY;
__HAL_UART_DISABLE(huart); /* Disable the peripheral */
UART_SetConfig(huart);/* Set the UART Communication parameters */
/* 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));
__HAL_UART_ENABLE(huart); /* Enable the peripheral */
huart->ErrorCode = HAL_UART_ERROR_NONE;
huart->gState = HAL_UART_STATE_READY;
huart->RxState = HAL_UART_STATE_READY;
調用MspInit-->修改狀態忙-->配置寄存器-->清楚標誌位
2.2 先理解HAL_UART_Receive函數
uint32_t tickstart = 0U;
if (huart->RxState == HAL_UART_STATE_READY) /* Check that a Rx process is not already ongoing */
{
__HAL_LOCK(huart); /* Process Locked */
huart->ErrorCode = HAL_UART_ERROR_NONE;
huart->RxState = HAL_UART_STATE_BUSY_RX;
tickstart = HAL_GetTick();
huart->RxXferSize = Size;
huart->RxXferCount = Size;
while (huart->RxXferCount > 0U)
{
huart->RxXferCount--;
if (UART_WaitOnFlagUntilTimeout(huart, UART_FLAG_RXNE, RESET, tickstart, Timeout) != HAL_OK)
return HAL_TIMEOUT;
*pData++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF);
}
}
huart->RxState = HAL_UART_STATE_READY;
__HAL_UNLOCK(huart);
判斷是否忙-->鎖住-->標記接收忙-->獲取tick計數
-->賦值RxXferCount有多少數據要接收-->每次從DR內獲取一個Byte存在pData指向的空間
2.3 HAL_UART_Receive_IT只是配置了一下參數，並沒有做任何處理
/* Check that a Rx process is not already ongoing */
if (huart->RxState == HAL_UART_STATE_READY)
{
__HAL_LOCK(huart); /* Process Locked */
huart->pRxBuffPtr = pData;
huart->RxXferSize = Size;
huart->RxXferCount = Size;
huart->ErrorCode = HAL_UART_ERROR_NONE;
huart->RxState = HAL_UART_STATE_BUSY_RX;
__HAL_UNLOCK(huart); /* Process Unlocked */
/*Error Interrupt */
__HAL_UART_ENABLE_IT(huart, UART_IT_PE);
__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;
}
存儲在pData指向位置、空間大小RxXferSize 、接收計數RxXferCount ； 接收狀態忙；使能接收中斷
那麼當有數據來的時候，就需要依靠中斷函數來處理了。
2.4再看看中斷函數在做什麼
stm32f1xx_it.c內有定義USART1_IRQHandler，只調用了HAL_UART_IRQHandler函數，下面是
HAL_UART_IRQHandler具體內容
errorflags = (isrflags & (uint32_t)(USART_SR_PE | USART_SR_FE | USART_SR_ORE | USART_SR_NE));
if (errorflags == RESET)
{
if (((isrflags & USART_SR_RXNE) != RESET) && ((cr1its & USART_CR1_RXNEIE) != RESET))
{
UART_Receive_IT(huart);
return;
}
}
/* If some errors occur */
if ((errorflags != RESET) && (((cr3its & USART_CR3_EIE) != RESET) || ((cr1its & (USART_CR1_RXNEIE | USART_CR1_PEIE)) != RESET)))
{
//略過錯誤處理
/* Call UART Error Call back function if need be --------------------------*/
if (huart->ErrorCode != HAL_UART_ERROR_NONE)
{
/* UART in mode Receiver -----------------------------------------------*/
if (((isrflags & USART_SR_RXNE) != RESET) && ((cr1its & USART_CR1_RXNEIE) != RESET))
UART_Receive_IT(huart);
//略過錯誤處理
huart->ErrorCode = HAL_UART_ERROR_NONE;
}
}
return;
} /* End if some error occurs */
/* UART in mode Transmitter ------------------------------------------------*/
if (((isrflags & USART_SR_TXE) != RESET) && ((cr1its & USART_CR1_TXEIE) != RESET))
{ UART_Transmit_IT(huart); return; }
/* UART in mode Transmitter end --------------------------------------------*/
if (((isrflags & USART_SR_TC) != RESET) && ((cr1its & USART_CR1_TCIE) != RESET))
{ UART_EndTransmit_IT(huart); return; }
無非是三件事，判斷是由什麼中斷響應的，有錯誤則處理，響應要調用的接收或者發送。
注意區別 UART_Receive_IT 和 HAL_UART_Receive_IT。
HAL_UART_Receive_IT是用戶調用的需要接收多少數據存在何處。
UART_Receive_IT是中斷調用的有數據收到該如何處理。
2.5 UART_Receive_IT 真正在接收數據的函數，但在最後會關閉中斷
uint16_t *tmp;
/* Check that a Rx process is ongoing */
if (huart->RxState == HAL_UART_STATE_BUSY_RX)
{
*huart->pRxBuffPtr++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF);
if (--huart->RxXferCount == 0U)
{
__HAL_UART_DISABLE_IT(huart, UART_IT_RXNE);
__HAL_UART_DISABLE_IT(huart, UART_IT_PE);
__HAL_UART_DISABLE_IT(huart, UART_IT_ERR);
huart->RxState = HAL_UART_STATE_READY;
#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);
#endif /* USE_HAL_UART_REGISTER_CALLBACKS */
return HAL_OK;
}
return HAL_OK;
}
如果是接收狀態忙，則從DR中讀取1Byte數據。
如果接收計數歸零，則使中斷失效，並調用回調函數（用戶定義則調用用戶的，否則調用系統的）
至此，所有用到的代碼分析完畢
三、總結
1、HAL_UART_Receive_IT和HAL_UART_Receive的區別就是：中斷接收是有數據到了纔去讀；直接接收是直接讀取，如果超時就返回
2、HAL_UART_Receive_IT配置後，有數據來，計數會在調用中斷函數之後自動減1。只有到計數爲0時，纔會關閉中斷並調用回調函數。至此有數據來不再調用中斷函數，因爲中斷已經失效。
3、HAL_UART_Receive_IT在計數未至0之前，應該可以讀取之前接收到的數據，但這樣做應該比較危險。
4、在開源電子的例程中，使用 HAL_UART_Receive_IT(&huart1,(uint8_t *)aRxBuffer, 1); 即Size設置爲1，只接收1Byte數據，在每次中斷結束後重新配置來使能中斷。
四、還有必要再看一眼uart的結構體定義
/**
* @brief UART handle Structure definition
*/
typedef struct __UART_HandleTypeDef
{
USART_TypeDef *Instance; /*!< UART registers base address */
UART_InitTypeDef Init; /*!< UART communication parameters */
uint8_t *pTxBuffPtr; /*!< Pointer to UART Tx transfer Buffer */
uint16_t TxXferSize; /*!< UART Tx Transfer size */
__IO uint16_t TxXferCount; /*!< UART Tx Transfer Counter */
uint8_t *pRxBuffPtr; /*!< Pointer to UART Rx transfer Buffer */
uint16_t RxXferSize; /*!< UART Rx Transfer size */
__IO uint16_t RxXferCount; /*!< UART Rx Transfer Counter */
DMA_HandleTypeDef *hdmatx; /*!< UART Tx DMA Handle parameters */
DMA_HandleTypeDef *hdmarx; /*!< UART Rx DMA Handle parameters */
HAL_LockTypeDef Lock; /*!< Locking object */
__IO HAL_UART_StateTypeDef gState; /*!< UART state information related to global Handle management
and also related to Tx operations.
This parameter can be a value of @ref HAL_UART_StateTypeDef */
__IO HAL_UART_StateTypeDef RxState; /*!< UART state information related to Rx operations.
This parameter can be a value of @ref HAL_UART_StateTypeDef */
__IO uint32_t ErrorCode; /*!< UART Error code */
#if (USE_HAL_UART_REGISTER_CALLBACKS == 1)
void (* TxHalfCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Tx Half Complete Callback */
void (* TxCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Tx Complete Callback */
void (* RxHalfCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Rx Half Complete Callback */
void (* RxCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Rx Complete Callback */
void (* ErrorCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Error Callback */
void (* AbortCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Abort Complete Callback */
void (* AbortTransmitCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Abort Transmit Complete Callback */
void (* AbortReceiveCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Abort Receive Complete Callback */
void (* WakeupCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Wakeup Callback */
void (* MspInitCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Msp Init callback */
void (* MspDeInitCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Msp DeInit callback */
#endif /* USE_HAL_UART_REGISTER_CALLBACKS */
} UART_HandleTypeDef;