写一段usart8使用DMA代码

以下是使用USART8和DMA进行数据传输的示例代码：

#include "stm32f4xx.h"

#define BUFFER_SIZE 32

uint8_t tx_buffer[BUFFER_SIZE] = "Hello, world!";
uint8_t rx_buffer[BUFFER_SIZE];

void DMA1_Stream6_IRQHandler(void)
{
  if (DMA1->HISR & DMA_HISR_TCIF6)
  {
    DMA1->HIFCR |= DMA_HIFCR_CTCIF6; // Clear the transfer complete flag
  }
}

int main(void)
{
  // Enable clock for USART8 and DMA1
  RCC->APB1ENR |= RCC_APB1ENR_UART8EN;
  RCC->AHB1ENR |= RCC_AHB1ENR_DMA1EN;

  // Configure USART8 pins
  GPIOC->MODER |= GPIO_MODER_MODE1_1; // PC1 as USART8_TX
  GPIOC->MODER |= GPIO_MODER_MODE0_1; // PC0 as USART8_RX

  // Configure USART8
  USART8->BRR = 0x8B; // Baud rate = 115200
  USART8->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE; // Enable TX, RX, USART

  // Configure DMA1 Channel 5 (USART8 TX)
  DMA1_Stream6->CR = 0;
  DMA1_Stream6->CR |= DMA_SxCR_DIR_0; // Memory-to-peripheral mode
  DMA1_Stream6->CR |= DMA_SxCR_MINC; // Increment memory address after each transfer
  DMA1_Stream6->CR |= DMA_SxCR_PL_1; // Priority level = high
  DMA1_Stream6->CR |= DMA_SxCR_TCIE; // Transfer complete interrupt enable
  DMA1_Stream6->PAR = (uint32_t) &USART8->DR; // Peripheral address
  DMA1_Stream6->M0AR = (uint32_t) tx_buffer; // Memory address
  DMA1_Stream6->NDTR = BUFFER_SIZE; // Number of data to transfer

  // Enable DMA1 Channel 5 (USART8 TX)
  DMA1_Stream6->CR |= DMA_SxCR_EN;

  // Wait for TX DMA transfer complete
  while (!(DMA1->HISR & DMA_HISR_TCIF6));

  // Clear the transfer complete flag
  DMA1->HIFCR |= DMA_HIFCR_CTCIF6;

  // Configure DMA1 Channel 2 (USART8 RX)
  DMA1_Stream1->CR = 0;
  DMA1_Stream1->CR |= DMA_SxCR_DIR_1; // Peripheral-to-memory mode
  DMA1_Stream1->CR |= DMA_SxCR_MINC; // Increment memory address after each transfer
  DMA1_Stream1->CR |= DMA_SxCR_PL_1; // Priority level = high
  DMA1_Stream1->CR |= DMA_SxCR_TCIE; // Transfer complete interrupt enable
  DMA1_Stream1->PAR = (uint32_t) &USART8->DR; // Peripheral address
  DMA1_Stream1->M0AR = (uint32_t) rx_buffer; // Memory address
  DMA1_Stream1->NDTR = BUFFER_SIZE; // Number of data to transfer

  // Enable DMA1 Channel 2 (USART8 RX)
  DMA1_Stream1->CR |= DMA_SxCR_EN;

  // Wait for RX DMA transfer complete
  while (!(DMA1->HISR & DMA_HISR_TCIF1));

  // Clear the transfer complete flag
  DMA1->HIFCR |= DMA_HIFCR_CTCIF1;

  // Print received data
  for (int i = 0; i < BUFFER_SIZE; i++)
  {
    printf("%c", rx_buffer[i]);
  }

  while (1);
}

此代码将使用DMA进行USART8的数据传输，其中TX数据存储在`tx_buffer`数组中，RX数据存储在`rx_buffer`数组中。我们使用DMA1的通道5进行USART8 TX传输，并使用DMA1的通道2进行USART8 RX传输。在传输完成后，可以从`rx_buffer`中读取接收到的数据。请注意，此示例代码中未包含中断处理程序的完整实现。