STM32F407使用标准库，串口USART2通过DMA使用乒乓缓冲来接收和发送数据

好的，这是一个比较常见的应用场景。我可以给你提供一些思路和代码片段来实现这个功能。

1. 配置USART2串口

首先，你需要使用标准库函数来配置USART2串口。你需要设置波特率、数据位、停止位、校验位等参数。下面是一个示例代码：

#include "stm32f4xx.h"

// 配置USART2串口
void USART2_Init(void)
{
    USART_InitTypeDef USART_InitStruct;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

    USART_InitStruct.USART_BaudRate = 115200;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

    USART_Init(USART2, &USART_InitStruct);

    USART_Cmd(USART2, ENABLE);
}

2. 配置DMA

接下来，你需要配置DMA。DMA可以帮助你实现高效的数据传输。你需要配置DMA的通道、数据传输方向、数据缓冲区地址等参数。下面是一个示例代码：

#include "stm32f4xx.h"

// 配置DMA
void DMA_Init(void)
{
    DMA_InitTypeDef DMA_InitStruct;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);

    DMA_InitStruct.DMA_Channel = DMA_Channel_4;
    DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&USART2->DR;
    DMA_InitStruct.DMA_Memory0BaseAddr = (uint32_t)buffer1;
    DMA_InitStruct.DMA_DIR = DMA_DIR_PeripheralToMemory;
    DMA_InitStruct.DMA_BufferSize = BUFFER_SIZE;
    DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStruct.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStruct.DMA_Priority = DMA_Priority_High;
    DMA_InitStruct.DMA_FIFOMode = DMA_FIFOMode_Disable;
    DMA_InitStruct.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
    DMA_InitStruct.DMA_MemoryBurst = DMA_MemoryBurst_Single;
    DMA_InitStruct.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;

    DMA_Init(DMA1_Stream5, &DMA_InitStruct);

    DMA_Cmd(DMA1_Stream5, ENABLE);
}

在这个示例中，我们使用了DMA1的Stream5通道，将数据从USART2的DR寄存器传输到缓冲区buffer1中。我们设置了循环模式，这样当缓冲区满了之后就会自动从缓冲区开头重新开始存储数据。

3. 配置乒乓缓冲区

为了避免在数据传输期间出现数据冲突，你需要使用乒乓缓冲区来处理数据。乒乓缓冲区就是在两个缓冲区之间进行切换，当一个缓冲区被DMA传输完毕后，另一个缓冲区就会被用来存储新的数据。下面是一个示例代码：

#include "stm32f4xx.h"

#define BUFFER_SIZE 1024

uint8_t buffer1[BUFFER_SIZE];
uint8_t buffer2[BUFFER_SIZE];
volatile uint8_t *pRX = buffer1;
volatile uint8_t *pTX = buffer2;

// USART2 DMA发送数据
void USART2_DMA_Send(uint8_t *pData, uint16_t Length)
{
    while(DMA_GetFlagStatus(DMA1_Stream6, DMA_FLAG_TCIF6) == RESET);

    DMA_ClearFlag(DMA1_Stream6, DMA_FLAG_TCIF6);
    DMA_Cmd(DMA1_Stream6, DISABLE);

    DMA_SetCurrDataCounter(DMA1_Stream6, Length);
    DMA_MemoryTargetConfig(DMA1_Stream6, (uint32_t)pData, DMA_Memory_0);
    DMA_Cmd(DMA1_Stream6, ENABLE);
}

// USART2 DMA接收数据
void USART2_DMA_Receive(void)
{
    if(DMA_GetFlagStatus(DMA1_Stream5, DMA_FLAG_TCIF5) != RESET)
    {
        DMA_ClearFlag(DMA1_Stream5, DMA_FLAG_TCIF5);

        // 处理接收到的数据
        // ...

        if(pRX == buffer1)
        {
            // 切换到buffer2
            DMA_MemoryTargetConfig(DMA1_Stream5, (uint32_t)pTX, DMA_Memory_0);
            pRX = buffer2;
            pTX = buffer1;
        }
        else
        {
            // 切换到buffer1
            DMA_MemoryTargetConfig(DMA1_Stream5, (uint32_t)pTX, DMA_Memory_0);
            pRX = buffer1;
            pTX = buffer2;
        }

        // 重新启动DMA传输
        DMA_Cmd(DMA1_Stream5, ENABLE);
    }
}

在这个示例中，我们使用了两个缓冲区buffer1和buffer2，并且定义了两个指针pRX和pTX来指向当前使用的缓冲区。当DMA传输完成后，我们会检查当前使用的缓冲区，并且切换到另一个缓冲区来存储新的数据。然后重新启动DMA传输，以便继续接收数据。

4. 发送和接收数据

最后，你需要编写代码来发送和接收数据。你可以使用USART_SendData函数来发送数据，使用USART_ReceiveData函数来接收数据。下面是一个示例代码：

#include "stm32f4xx.h"

#define BUFFER_SIZE 1024

uint8_t buffer1[BUFFER_SIZE];
uint8_t buffer2[BUFFER_SIZE];
volatile uint8_t *pRX = buffer1;
volatile uint8_t *pTX = buffer2;

// 配置USART2串口
void USART2_Init(void)
{
    USART_InitTypeDef USART_InitStruct;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

    USART_InitStruct.USART_BaudRate = 115200;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

    USART_Init(USART2, &USART_InitStruct);

    USART_Cmd(USART2, ENABLE);
}

// 配置DMA
void DMA_Init(void)
{
    DMA_InitTypeDef DMA_InitStruct;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);

    DMA_InitStruct.DMA_Channel = DMA_Channel_4;
    DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&USART2->DR;
    DMA_InitStruct.DMA_Memory0BaseAddr = (uint32_t)buffer1;
    DMA_InitStruct.DMA_DIR = DMA_DIR_PeripheralToMemory;
    DMA_InitStruct.DMA_BufferSize = BUFFER_SIZE;
    DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStruct.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStruct.DMA_Priority = DMA_Priority_High;
    DMA_InitStruct.DMA_FIFOMode = DMA_FIFOMode_Disable;
    DMA_InitStruct.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
    DMA_InitStruct.DMA_MemoryBurst = DMA_MemoryBurst_Single;
    DMA_InitStruct.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;

    DMA_Init(DMA1_Stream5, &DMA_InitStruct);

    DMA_Cmd(DMA1_Stream5, ENABLE);
}

// USART2 DMA发送数据
void USART2_DMA_Send(uint8_t *pData, uint16_t Length)
{
    while(DMA_GetFlagStatus(DMA1_Stream6, DMA_FLAG_TCIF6) == RESET);

    DMA_ClearFlag(DMA1_Stream6, DMA_FLAG_TCIF6);
    DMA_Cmd(DMA1_Stream6, DISABLE);

    DMA_SetCurrDataCounter(DMA1_Stream6, Length);
    DMA_MemoryTargetConfig(DMA1_Stream6, (uint32_t)pData, DMA_Memory_0);
    DMA_Cmd(DMA1_Stream6, ENABLE);
}

// USART2 DMA接收数据
void USART2_DMA_Receive(void)
{
    if(DMA_GetFlagStatus(DMA1_Stream5, DMA_FLAG_TCIF5) != RESET)
    {
        DMA_ClearFlag(DMA1_Stream5, DMA_FLAG_TCIF5);

        // 处理接收到的数据
        // ...

        if(pRX == buffer1)
        {
            // 切换到buffer2
            DMA_MemoryTargetConfig(DMA1_Stream5, (uint32_t)pTX, DMA_Memory_0);
            pRX = buffer2;
            pTX = buffer1;
        }
        else
        {
            // 切换到buffer1
            DMA_MemoryTargetConfig(DMA1_Stream5, (uint32_t)pTX, DMA_Memory_0);
            pRX = buffer1;
            pTX = buffer2;
        }

        // 重新启动DMA传输
        DMA_Cmd(DMA1_Stream5, ENABLE);
    }
}

int main(void)
{
    USART2_Init();
    DMA_Init();

    while(1)
    {
        // 发送数据
        uint8_t data[] = "Hello World!";
        USART2_DMA_Send(data, sizeof(data));

        // 接收数据
        USART2_DMA_Receive();
    }
}

这个示例代码中，我们在主循环中不断发送和接收数据。当需要发送数据时，我们调用USART2_DMA_Send函数，并传入要发送的数据和数据长度。当需要接收数据时，我们调用USART2_DMA_Receive函数。在接收到数据后，我们会对数据进行处理，并且切换到另一个缓冲区来存储新的数据。