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怎么使用这个函数初始化串口3HAL_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. Except for STM32F446xx devices, that is available for USART1, USART2, USART3, USART6, UART4 and UART5. / 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; #if (USE_HAL_UART_REGISTER_CALLBACKS == 1) UART_InitCallbacksToDefault(huart); if (huart->MspInitCallback == NULL) { huart->MspInitCallback = HAL_UART_MspInit; } / Init the low level hardware / huart->MspInitCallback(huart); #else / Init the low level hardware : GPIO, CLOCK / HAL_UART_MspInit(huart); #endif / (USE_HAL_UART_REGISTER_CALLBACKS) / } 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; }

这个函数是用来初始化UART串口的，具体的使用方法如下： 1. 首先需要定义一个`UART_HandleTypeDef`类型的结构体变量`huart`，并对其中的各个成员变量进行配置，例如： ``` UART_HandleTypeDef huart; huart.Instance = USART3; huart.Init.BaudRate = 115200; huart.Init.WordLength = UART_WORDLENGTH_8B; huart.Init.StopBits = UART_STOPBITS_1; huart.Init.Parity = UART_PARITY_NONE; huart.Init.Mode = UART_MODE_TX_RX; huart.Init.HwFlowCtl = UART_HWCONTROL_NONE; huart.Init.OverSampling = UART_OVERSAMPLING_16; ``` 2. 调用`HAL_UART_Init()`函数进行初始化，将上述结构体变量传入该函数即可。 ``` HAL_StatusTypeDef result = HAL_UART_Init(&huart); if (result != HAL_OK) { // 初始化失败，进行错误处理 } else { // 初始化成功，进行后续操作 } ``` 在该函数内部，会先进行一些参数检查，然后根据参数配置寄存器，最终完成UART串口的初始化。

这个函数怎么使用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. Except for STM32F446xx devices, that is available for USART1, USART2, USART3, USART6, UART4 and UART5. / 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; #if (USE_HAL_UART_REGISTER_CALLBACKS == 1) UART_InitCallbacksToDefault(huart); if (huart->MspInitCallback == NULL) { huart->MspInitCallback = HAL_UART_MspInit; } / Init the low level hardware / huart->MspInitCallback(huart); #else / Init the low level hardware : GPIO, CLOCK / HAL_UART_MspInit(huart); #endif / (USE_HAL_UART_REGISTER_CALLBACKS) / } 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; }

这个函数是HAL库（STM32的驱动库）中的UART初始化函数，用于初始化指定的UART外设。它的参数是一个UART_HandleTypeDef类型的指针，其中包含了UART的初始化参数和外设的实例。函数执行过程中会进行一系列的参数检查，包括检查参数是否为空、硬件流控制是否可用、数据位长度是否合法等等。如果UART的gState状态为HAL_UART_STATE_RESET，那么它会先初始化底层硬件资源（包括GPIO和时钟），否则会直接进行配置和使能。最后，函数会将UART的状态设置为HAL_UART_STATE_READY，表示初始化完成。

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