stm32 DMA + 串口发送不定长数据 标准库函数代码

以下是一个基于STM32的DMA+串口发送不定长数据的示例代码，使用了标准库函数。

首先需要初始化串口和DMA：

#include "stm32fxxx.h"
#include <string.h>

#define BUFFER_SIZE 256

uint8_t buffer[BUFFER_SIZE];
uint16_t buffer_length = 0;

void init_USART1(uint32_t baudrate)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    USART_InitStructure.USART_BaudRate = baudrate;
    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_Init(USART1, &USART_InitStructure);

    USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
    USART_Cmd(USART1, ENABLE);
}

void init_DMA1(uint8_t* buffer, uint16_t length)
{
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    DMA_InitTypeDef DMA_InitStructure;

    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) & (USART1->DR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) buffer;
    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_VeryHigh;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel4, &DMA_InitStructure);
}

然后，可以编写一个函数来发送数据。该函数将数据添加到缓冲区中，并启动DMA传输：

void send_data(uint8_t* data, uint16_t length)
{
    if (length > BUFFER_SIZE) {
        length = BUFFER_SIZE;
    }
    if (buffer_length + length > BUFFER_SIZE) {
        length = BUFFER_SIZE - buffer_length;
    }
    memcpy(buffer + buffer_length, data, length);
    buffer_length += length;
    if (DMA_GetFlagStatus(DMA1_FLAG_TC4) == SET) {
        DMA_Cmd(DMA1_Channel4, DISABLE);
        DMA_SetCurrDataCounter(DMA1_Channel4, buffer_length);
        DMA_Cmd(DMA1_Channel4, ENABLE);
        buffer_length = 0;
    }
}

在主函数中，可以使用此函数来发送数据：

int main()
{
    init_USART1(9600);
    init_DMA1(buffer, 0);
    uint8_t data[] = "Hello World!";
    send_data(data, strlen(data));
    while (1);
}

当缓冲区满时，DMA传输将启动。每次DMA传输完成时，都会重新启动DMA传输。