stm32f103 DMA +串口发送不定长数据 标准库函数代码示例

以下是一个基于STM32F103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 "stm32f1xx.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->APB2ENR |= RCC_APB2ENR_USART1EN | RCC_APB2ENR_IOPAEN;
    GPIOA->CRH |= GPIO_CRH_MODE9_0 | GPIO_CRH_MODE9_1 | GPIO_CRH_CNF9_1;
    GPIOA->CRH &= ~(GPIO_CRH_CNF9_0);
    USART1->BRR = SystemCoreClock / baudrate;
    USART1->CR1 |= USART_CR1_TE;
    USART1->CR3 |= USART_CR3_DMAT;
    USART1->CR1 |= USART_CR1_UE;
}

void init_DMA1(uint8_t* buffer, uint16_t length)
{
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
    DMA1_Channel4->CPAR = (uint32_t) & (USART1->DR);
    DMA1_Channel4->CMAR = (uint32_t) buffer;
    DMA1_Channel4->CNDTR = length;
    DMA1_Channel4->CCR |= DMA_CCR_DIR | DMA_CCR_MINC | DMA_CCR_TCIE | DMA_CCR_EN;
}

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 (DMA1_Channel4->CNDTR == 0) {
        DMA1_Channel4->CCR &= ~DMA_CCR_EN;
        DMA1_Channel4->CNDTR = buffer_length;
        DMA1_Channel4->CCR |= DMA_CCR_EN;
        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。