STM32F1 USART2 DMA查询方式收发数据

现有一个小需求，使用STM32F1系列单片机做串口2的收发数据的功能，通过PC上的串口调试助手给单片机发一串数据，单片机收到数据后再给PC的串口调试助手发回去。

本次使用的是串口DMA方式接收数据，和DMA方式发送数据。

STM32使用USART2，对应单片机的PA1控制方向，PA2发送，PA3接收。

代码如下：

main.c

#include "stm32f10x.h"

#include 

#define LEN_DMA_RECV_BUF 256

u16 len_dma_recv;
u8 dma_recv_buf[LEN_DMA_RECV_BUF];
u8 usart2_cache[LEN_DMA_RECV_BUF];
u8 dma_send_buf[LEN_DMA_RECV_BUF];

void init_hardware_usart2_dma(u32 bound)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	DMA_InitTypeDef DMA_InitStructure;
	
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
	
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	GPIO_Init(GPIOA, &GPIO_InitStructure);

	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
	GPIO_Init(GPIOA, &GPIO_InitStructure);

	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
	GPIO_Init(GPIOA, &GPIO_InitStructure);
	
	USART_InitStructure.USART_BaudRate = bound;
	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_Rx | USART_Mode_Tx;
	USART_Init(USART2, &USART_InitStructure);
	
	DMA_DeInit(DMA1_Channel6);
	DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART2->DR;
	DMA_InitStructure.DMA_MemoryBaseAddr = (u32)dma_recv_buf;
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
	DMA_InitStructure.DMA_BufferSize = LEN_DMA_RECV_BUF;
	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_Channel6, &DMA_InitStructure);
	DMA_Cmd(DMA1_Channel6, ENABLE);
	
	DMA_DeInit(DMA1_Channel7);
	DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART2->DR;
	DMA_InitStructure.DMA_MemoryBaseAddr = (u32)dma_send_buf;
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
	DMA_InitStructure.DMA_BufferSize = 0;
	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;
	DMA_Init(DMA1_Channel7, &DMA_InitStructure);
	DMA_Cmd(DMA1_Channel7, DISABLE);
	DMA_ClearFlag(DMA1_FLAG_GL7);
	
	GPIO_ResetBits(GPIOA, GPIO_Pin_1);
	
	USART_Cmd(USART2, ENABLE);
	USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);
	USART_DMACmd(USART2, USART_DMAReq_Tx, ENABLE);
}

void func_usart2_dma_send_bytes(u8 *bytes, u8 bytes_len)
{
	GPIO_SetBits(GPIOA, GPIO_Pin_1);
	DMA_Cmd(DMA1_Channel7, DISABLE);
	memcpy(dma_send_buf, bytes, bytes_len);
	DMA_SetCurrDataCounter(DMA1_Channel7, bytes_len);
	DMA_Cmd(DMA1_Channel7, ENABLE);
	while(DMA_GetCurrDataCounter(DMA1_Channel7));
	while(USART_GetFlagStatus(USART2, USART_FLAG_TC) != SET);
	GPIO_ResetBits(GPIOA, GPIO_Pin_1);
}

int main()
{
	init_hardware_usart2_dma(9600);
	
	while(1)
	{
		if(USART_GetFlagStatus(USART2, USART_FLAG_IDLE) != RESET)
		{
			USART_ReceiveData(USART2);
			DMA_Cmd(DMA1_Channel6, DISABLE);
			len_dma_recv = LEN_DMA_RECV_BUF - DMA_GetCurrDataCounter(DMA1_Channel6);
			memcpy(usart2_cache, dma_recv_buf, len_dma_recv);
			memset(dma_recv_buf, 0, len_dma_recv);
			DMA_SetCurrDataCounter(DMA1_Channel6, LEN_DMA_RECV_BUF);
			USART_ClearFlag(USART2, USART_FLAG_IDLE);
			DMA_Cmd(DMA1_Channel6, ENABLE);
			func_usart2_dma_send_bytes(usart2_cache, len_dma_recv);
			
		}
	}
}

需要注意的问题1：

在DMA方式接收数据时，需要将USART_FLAG_IDLE清除，清除的方式为

USART_GetFlagStatus(USART2, USART_FLAG_IDLE)方法查看源代码，有读SR寄存器。USART_ReceiveData(USART2)方法查看源码有读DR寄存器。

需要注意的问题2：

DMA方式发送数据时，需要判断是否发送完成了。

while(USART_GetFlagStatus(USART2, USART_FLAG_TC) != SET);

通过该方法判断发送是否完成，如果未发送完成，继续等待，直到发送完成。

代码执行后，效果如下：

STM32接收了串口调试助手发送的5万多条数据，并成功发送给串口调试助手。

测试代码，仅供参考。