UART通过DMA接收和发送，使用环形缓冲区，状态机的使用

前言

为了实现UART通过DMA接收和发送不定长度的数据，可以使用环形缓冲区（环形缓冲区）和插入相关的状态机来解析接收到的数据。

步骤

1.启用时钟，配置引脚，配置USART，配置DMA，这些不用说了吧，官方教程有一堆
2.DMA 接收处理，DMA 接收完成中断，这个没什么用，接收到的数据长度不一，DMA只要负责把UART的数据寄存器的数据搬到内存中就行了。
3.UART的接收处理和状态机解析，在UART接收完成中断中，需要处理内存的数据和和状态机解析。
4.UART的发送函数中再初始化txBuffer的DMA，因为每次发送的length不一样。

具体代码

1.初始化 DMA 和 UART：

#define RX_BUFFER_SIZE 1024  // 环形缓冲区大小
#define TX_BUFFER_SIZE 150   // 发送缓冲区大小uint8_t rxBuffer[RX_BUFFER_SIZE];
uint8_t txBuffer[TX_BUFFER_SIZE];volatile uint16_t rxWriteIndex = 0;void UART_DMA_Init(void) {USART_InitTypeDef USART_InitStructure;DMA_InitTypeDef DMA_InitStructure;GPIO_InitTypeDef GPIO_InitStructure;// 启用时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);// 配置UART引脚GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; // TXGPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_Init(GPIOA, &GPIO_InitStructure);GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; // RXGPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);// 配置USARTUSART_InitStructure.USART_BaudRate = 115200;USART_InitStructure.USART_WordLength = USART_WordLength_8b;USART_InitStructure.USART_StopBits = USART_StopBits_1;USART_InitStructure.USART_Parity = USART_Parity_No;USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;USART_Init(USART1, &USART_InitStructure);// 配置DMA RXDMA_DeInit(DMA1_Channel5);DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART1->DR;DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)rxBuffer;DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;DMA_InitStructure.DMA_BufferSize = RX_BUFFER_SIZE;DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;DMA_InitStructure.DMA_Priority = DMA_Priority_High;DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;DMA_Init(DMA1_Channel5, &DMA_InitStructure);// 启用DMAUSART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE);DMA_Cmd(DMA1_Channel5, ENABLE);// 启用USARTUSART_Cmd(USART1, ENABLE);
}

2.DMA 接收处理和状态机解析：

void DMA1_Channel5_IRQHandler(void) {if (DMA_GetITStatus(DMA1_IT_TC5)) {DMA_ClearITPendingBit(DMA1_IT_TC5);// 传输完成}
}void USART1_IRQHandler(void) {if (USART_GetITStatus(USART1, USART_IT_IDLE) != RESET) {volatile uint32_t temp;temp = USART1->SR;  // 读取USART SR寄存器temp = USART1->DR;  // 读取USART DR寄存器以清除IDLE中断标志uint16_t rxIndex = RX_BUFFER_SIZE - DMA_GetCurrDataCounter(DMA1_Channel5);if (rxIndex != rxWriteIndex) {if (rxIndex > rxWriteIndex) {ProcessReceivedData(&rxBuffer[rxWriteIndex], rxIndex - rxWriteIndex);} else {ProcessReceivedData(&rxBuffer[rxWriteIndex], RX_BUFFER_SIZE - rxWriteIndex);ProcessReceivedData(&rxBuffer[0], rxIndex);}rxWriteIndex = rxIndex;}}
}void ProcessReceivedData(uint8_t *data, uint16_t length) {// 将接收到的数据传入状态机进行解析for (uint16_t i = 0; i < length; i++) {ParseStateMachine(data[i]);}
}void ParseStateMachine(uint8_t byte) {// 根据实际应用编写状态机解析代码
}

3.DMA 发送 UART 数据的代码及发送完处理逻辑

void UART_SendDataDMA(uint8_t *data, uint16_t length) {DMA_InitTypeDef DMA_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;// 配置 DMADMA_DeInit(DMA1_Channel4);  // 假设使用 DMA1 Channel4DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART1->DR;DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)data;DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;DMA_InitStructure.DMA_BufferSize = length;DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;DMA_InitStructure.DMA_Priority = DMA_Priority_High;DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;// 初始化 DMADMA_Init(DMA1_Channel4, &DMA_InitStructure);// 清除传输完成标志DMA_ClearFlag(DMA1_FLAG_TC4);// 配置 NVICNVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);// 使能 DMA传输完成中断DMA_ITConfig(DMA1_Channel4, DMA_IT_TC, ENABLE);// 使能 DMA 通道DMA_Cmd(DMA1_Channel4, ENABLE);// 使能 USART 的 DMA 传输请求USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
}
// DMA1 Channel4 中断处理
void DMA1_Channel4_IRQHandler(void)
{// 检查 DMA 传输完成中断标志if (DMA_GetITStatus(DMA1_IT_TC4)){// 清除传输完成中断标志DMA_ClearITPendingBit(DMA1_IT_TC4);// 禁用 DMA 通道DMA_Cmd(DMA1_Channel4, DISABLE);// 其他传输完成后的处理代码...}
}

4.主函数调用：

int main(void) {UART_DMA_Init();// 使能IDLE中断USART_ITConfig(USART1, USART_IT_IDLE, ENABLE);NVIC_EnableIRQ(USART1_IRQn);NVIC_EnableIRQ(DMA1_Channel4_IRQn);NVIC_EnableIRQ(DMA1_Channel5_IRQn);uint8_t dataToSend[] = "Hello World!";UART_SendDataDMA(dataToSend, sizeof(dataToSend) - 1);while (1) {// 主循环，中断处理和DMA完成发送接收}
}