STM32串口通信为什么会一直出现数据错位的问题呢

背景：两片STM32通过串口通信，为了减小CPU负担，采用DMA进行通信，发送端为STM32F103C8T6，接收端为STM32F407VET6。在调试的过程中发现，一直出现数据错位的问题，接收端尝试了串口空闲中断和串口DMA传输完成中断，错位问题依旧，其实我之前遇到过这个问题，那次发送端没有使用DMA，而是直接用串口发送，接收端采用DMA接收完成中断，检测到错位后，延时重置DMA，直到DMA接收同步后，不再重置，此后DMA便会保持同步，不会错位。但是这次不知道为什么采用上次的方法没有解决，因此决定直接用最简单粗暴的方法——查找，但是弊端是会在中断中运行一段比较占空时间的代码。

说明：主要部分在接收中断（本文最后的代码段），发送端发送的DMA数据长度为a，接收端DMA配置的BufferSize为2a，这样即使错位，在2a的数据长度中也一定会存在一段完整的有效数据。接收中断中，在接收buffer的前半段查找帧头，找到之后，判断帧头+a-1的位置是否是帧尾，如果是，则基本可以认为中间即为有效数据，将该段数据拷贝到一个新的数组中，等待解析。

配置部分：发送端 STM32F103C8T6



/* uart3 for communicate with the master */
void vUart3Config(void)
{
        GPIO_InitTypeDef         GPIO_InitStructure;
        USART_InitTypeDef       USART_InitStructure;
        NVIC_InitTypeDef         NVIC_InitStructure;
        DMA_InitTypeDef                DMA_InitStructure;
         
        RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
        RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
       
        /* USART3_RX          GPIOB.11 */
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
        GPIO_Init(GPIOB, &GPIO_InitStructure);  

        /* USART3_TX   GPIOB.10 */
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
        GPIO_Init(GPIOB, &GPIO_InitStructure);
       
        NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure);

        USART_InitStructure.USART_BaudRate = 115200;
        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(USART3, &USART_InitStructure);
       
        USART_Cmd(USART3, ENABLE);
        USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
       
        { /* send dma */
                USART_DMACmd(USART3,USART_DMAReq_Tx,ENABLE);
               
                DMA_DeInit(DMA1_Channel2);
                DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&(USART3->DR));
                DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)SendToMaster_Buff;
                DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
                DMA_InitStructure.DMA_BufferSize = USART3_DMA_send_buffersize;
                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_Circular;
                DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
                DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
                DMA_Init(DMA1_Channel2,&DMA_InitStructure);

                NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel2_IRQn;           
                NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;         
                NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
                NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
                NVIC_Init(&NVIC_InitStructure);
               
                DMA_ITConfig(DMA1_Channel2,DMA_IT_TC,ENABLE);
               
                DMA_Cmd(DMA1_Channel2,ENABLE);
        }
}

配置部分：接收端 STM32F407VET6


void vUTConfig(void)
{
        USART_InitTypeDef usart;
        GPIO_InitTypeDef  gpio;
        NVIC_InitTypeDef  nvic;
        DMA_InitTypeDef   dma;

        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);

        GPIO_PinAFConfig(GPIOA,GPIO_PinSource9 ,GPIO_AF_USART1);
        GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_USART1);
       
        /* USART1_RX          GPIOA.10 */
        gpio.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10;
        gpio.GPIO_Mode = GPIO_Mode_AF;
        gpio.GPIO_OType = GPIO_OType_PP;
        gpio.GPIO_Speed = GPIO_Speed_100MHz;
        gpio.GPIO_PuPd = GPIO_PuPd_NOPULL;
        GPIO_Init(GPIOA,&gpio);

        usart.USART_BaudRate = 115200;
        usart.USART_WordLength = USART_WordLength_8b;
        usart.USART_StopBits = USART_StopBits_1;
        usart.USART_Parity = USART_Parity_No;
        usart.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
        usart.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
        USART_Init(USART1,&usart);
               
        USART_Cmd(USART1,ENABLE);

        { /* receive dma */
                USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);
               
                DMA_DeInit(DMA2_Stream2);
                dma.DMA_Channel= DMA_Channel_4;
                dma.DMA_PeripheralBaseAddr = (uint32_t)&(USART1->DR);
                dma.DMA_Memory0BaseAddr = (uint32_t)ReceiveFromUT_Buffer;
                dma.DMA_DIR = DMA_DIR_PeripheralToMemory;
                dma.DMA_BufferSize = USART1_UT_DMA_receive_buffersize;
                dma.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
                dma.DMA_MemoryInc = DMA_MemoryInc_Enable;
                dma.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
                dma.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
                dma.DMA_Mode = DMA_Mode_Circular;
                dma.DMA_Priority = DMA_Priority_VeryHigh;
                dma.DMA_FIFOMode = DMA_FIFOMode_Disable;
                dma.DMA_FIFOThreshold = DMA_FIFOThreshold_1QuarterFull;
                dma.DMA_MemoryBurst = DMA_MemoryBurst_Single;
                dma.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
                DMA_Init(DMA2_Stream2,&dma);
               
                nvic.NVIC_IRQChannel = DMA2_Stream2_IRQn;           
                nvic.NVIC_IRQChannelPreemptionPriority = 1;         
                nvic.NVIC_IRQChannelSubPriority = 1;
                nvic.NVIC_IRQChannelCmd = ENABLE;
                NVIC_Init(&nvic);
               
                DMA_ITConfig(DMA2_Stream2,DMA_IT_TC,ENABLE);
                DMA_Cmd(DMA2_Stream2,ENABLE);
        }
}
中断部分：发送中断


/* USART3 DMA send interrupt */
void DMA1_Channel2_IRQHandler(void)
{
        if(DMA_GetITStatus(DMA1_IT_TC2))
        {
                DMA_ClearFlag(DMA1_IT_TC2);
                DMA_ClearITPendingBit(DMA1_IT_TC2);
//                DMA_Cmd(DMA1_Channel2,DISABLE);
//                DMA_SetCurrDataCounter(DMA1_Channel2,USART3_DMA_send_buffersize);
//                DMA_Cmd(DMA1_Channel2, ENABLE);
        }
}
中断部分：接收中断



/* USART1 dma receive for ut */
void DMA2_Stream2_IRQHandler(void)
{
        uint8_t i = 0;
       
        if(DMA_GetFlagStatus(DMA2_Stream2,DMA_IT_TCIF2) == SET)
        {
                /* 在前半部分查找帧头并校验对应位置是否为帧尾 */
                for(i=0;i<(USART1_UT_DMA_receive_buffersize/2);i++)
                {
                        if((ReceiveFromUT_Buffer == 0x05)&&(ReceiveFromUT_Buffer[i+USART1_UT_DMA_receive_buffersize-1] == 0x06))
                        {
                                /* 拷贝有效数据段到待解析数组 */
                                memcpy(ReceiveFromUT_Data,&ReceiveFromUT_Buffer,USART1_UT_DMA_receive_buffersize/2);
                               
                                /* 数据解析 */
                                UTReceive();
                        }
                }
               
                /* 没有有效数据 */
                if(i >= USART1_UT_DMA_receive_buffersize/2)
                {
                        /* 重置DMA */
                        DMA_Cmd(DMA2_Stream2,DISABLE);
                        DMA_SetCurrDataCounter(DMA2_Stream2,USART1_UT_DMA_receive_buffersize);       
                        DMA_Cmd(DMA2_Stream2,ENABLE);
                }
               
                DMA_ClearFlag(DMA2_Stream2, DMA_FLAG_TCIF2);
                DMA_ClearITPendingBit(DMA2_Stream2, DMA_IT_TCIF2);               
        }
}