请教一个古怪的STM32F205的串口DMA接收问题

FSL_FAE_NEO 提问时间：2013-12-19 13:03 /

几乎是按照官方例子配出来的程序.  我是想设置4个字节到缓冲区后产生接收传输完成中断. 然后一次处理4个字节，但是PC只要向STM32发送1个字节，DMA_FLAG_TCIF1马上就置位了, 缓冲区里面也没有数据，但是看USART-DR里是收到那个字符的.

下面是初始化代码，为了简化我没有中断，配置好串口后一直查询 DMA_FLAG_TCIF1 标志位.

// 初始化函数，外面会传一个BUF首地址和长度进来作为DMA接收缓冲区
void HAL_UARTDevInit (const UINT8 *p_rec_buf, UINT32 num)
{
UINT8 err;

DMA_InitTypeDef dma_init_structure;
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);

/* Connect PXx to USARTx_Tx*/
GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_USART3);

/* Connect PXx to USARTx_Rx*/
GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_USART3);

/* Configure USART Tx as alternate function  */
GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_Init(GPIOB, &GPIO_InitStructure);

/* Configure USART Rx as alternate function  */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_Init(GPIOB, &GPIO_InitStructure);

/* USART configuration */
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_ClearFlag(USART3, USART_FLAG_TC | USART_FLAG_RXNE);                /* 清除已有的标志位, 防止使能后直接进入该中断 */
USART_Cmd(USART3, ENABLE);

/* 当配置DMA时初始化DMA接收通道 */
DMA_DeInit(DMA1_Stream1);

dma_init_structure.DMA_Channel          = DMA_Channel_4;
dma_init_structure.DMA_PeripheralBaseAddr = (uint32_t)(USART3 + 0x04);
dma_init_structure.DMA_Memory0BaseAddr = (uint32_t)p_rec_buf;
dma_init_structure.DMA_DIR             = DMA_DIR_PeripheralToMemory;
dma_init_structure.DMA_BufferSize       = num;
dma_init_structure.DMA_PeripheralInc    = DMA_PeripheralInc_Disable;
dma_init_structure.DMA_MemoryInc       = DMA_MemoryInc_Enable;
dma_init_structure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
dma_init_structure.DMA_MemoryDataSize    = DMA_MemoryDataSize_Byte;
dma_init_structure.DMA_Mode             = DMA_Mode_Normal;
dma_init_structure.DMA_Priority          = DMA_Priority_VeryHigh;
dma_init_structure.DMA_FIFOMode          = DMA_FIFOMode_Disable;
dma_init_structure.DMA_FIFOThreshold    = DMA_FIFOThreshold_Full;
dma_init_structure.DMA_MemoryBurst       = DMA_MemoryBurst_Single;
dma_init_structure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_Init(DMA1_Stream1, &dma_init_structure);

USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);
DMA_Cmd(DMA1_Stream1, ENABLE);
}

//测试代码
unsigned char buffer[4];

HAL_UARTDevInit(buffer, 4);
while (DMA_GetFlagStatus(DMA1_Stream1, DMA_FLAG_TCIF1) == RESET)
{
;
}
while(1); // 设个断点程序达到此处后停下来观察内存. 只要串口接受到1个字节就会到这里, buffer里全是0, 而USART3->DR里有我发过来的数据. 详细对比了几遍和例程 USART_TwoBoards\DataExchangeDMA.  几乎没有不同. 我禁止掉了FIFO模式, 如果启用FIFO也是一样

请高人帮忙！