**带有DMA的STM32f427 UART **从控制台接收数据时，最高位有时为1

使用STM32f427 UART和DMA（使用stm cube HAL库）时遇到问题 .

我想制作一个控制台回显函数，所以我在uart空闲中断处理函数中立即回复接收到的数据 .

但有时，当我在键盘输入任何键时，接收数据的最高位将为1 . 如下

0x31 -> 0xB1
0x32 -> 0xB2
0x40 -> 0xC0

有人有任何想法吗？代码段如下 .

非常感谢你 .

My uart configuration as following

uart_handler.Instance          = USARTx;
uart_handler.Init.BaudRate     = baudrate;
uart_handler.Init.WordLength   = UART_WORDLENGTH_8B;
uart_handler.Init.StopBits     = UART_STOPBITS_1;
uart_handler.Init.Parity       = UART_PARITY_NONE;
uart_handler.Init.HwFlowCtl    = UART_HWCONTROL_NONE;
uart_handler.Init.Mode         = UART_MODE_TX_RX;
uart_handler.Init.OverSampling = UART_OVERSAMPLING_8;

My PIN and DMA channels configuration as following

GPIO_InitStruct.Pin       = USARTx_TX_PIN;
GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull      = GPIO_PULLUP;
GPIO_InitStruct.Speed     = GPIO_SPEED_HIGH;
GPIO_InitStruct.Alternate = USARTx_TX_AF;
HAL_GPIO_Init(USARTx_TX_GPIO_PORT, &GPIO_InitStruct);
GPIO_InitStruct.Pin = USARTx_RX_PIN;
GPIO_InitStruct.Mode      = GPIO_MODE_AF_OD;
GPIO_InitStruct.Pull      = GPIO_NOPULL;
GPIO_InitStruct.Alternate = USARTx_RX_AF;
HAL_GPIO_Init(USARTx_RX_GPIO_PORT, &GPIO_InitStruct);
hdma_tx.Instance                 = USARTx_TX_DMA_STREAM;
hdma_tx.Init.Channel             = USARTx_TX_DMA_CHANNEL;
hdma_tx.Init.Direction           = DMA_MEMORY_TO_PERIPH;
hdma_tx.Init.PeriphInc           = DMA_PINC_DISABLE;
hdma_tx.Init.MemInc              = DMA_MINC_ENABLE;
hdma_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_tx.Init.MemDataAlignment    = DMA_MDATAALIGN_BYTE;
hdma_tx.Init.Mode                = DMA_NORMAL;
hdma_tx.Init.Priority            = DMA_PRIORITY_LOW;
hdma_tx.Init.FIFOMode            = DMA_FIFOMODE_DISABLE;
hdma_tx.Init.FIFOThreshold       = DMA_FIFO_THRESHOLD_FULL;
hdma_tx.Init.MemBurst            = DMA_MBURST_INC16;
hdma_tx.Init.PeriphBurst         = DMA_MBURST_INC16;
HAL_DMA_Init(&hdma_tx);

/ 将初始化的DMA句柄与UART句柄相关联 /

__HAL_LINKDMA(huart, hdmatx, hdma_tx);

/ 为接收过程配置DMA处理程序 /

hdma_rx.Instance                 = USARTx_RX_DMA_STREAM;
hdma_rx.Init.Channel             = USARTx_RX_DMA_CHANNEL;
hdma_rx.Init.Direction           = DMA_PERIPH_TO_MEMORY;
hdma_rx.Init.PeriphInc           = DMA_PINC_DISABLE;
hdma_rx.Init.MemInc              = DMA_MINC_ENABLE;
hdma_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_rx.Init.MemDataAlignment    = DMA_MDATAALIGN_BYTE;
hdma_rx.Init.Mode                = DMA_NORMAL;
hdma_rx.Init.Priority            = DMA_PRIORITY_HIGH;
hdma_rx.Init.FIFOMode            = DMA_FIFOMODE_DISABLE;
hdma_rx.Init.FIFOThreshold       = DMA_FIFO_THRESHOLD_FULL;
hdma_rx.Init.MemBurst            = DMA_MBURST_INC16;
hdma_rx.Init.PeriphBurst         = DMA_MBURST_INC16;

并使用uart空闲中断来接收数据 .

uint32_t temp;
if((__HAL_UART_GET_FLAG(huart, UART_FLAG_IDLE) != RESET))
{
__HAL_UART_CLEAR_IDLEFLAG(huart);
HAL_UART_DMAStop(&uart_handler);
temp = uart_handler.hdmarx->Instance->NDTR;
g_usart_info.rx_len =  USART_DMA_RECV_LEN - temp;
g_usart_info.receive_flag = 1;
g_usart_info.usart_dma_tx_buff = g_usart_info.usart_dma_rx_buff[0] ;
memset(g_usart_info.usart_dma_rx_buff, 0,                
sizeof(g_usart_info.usart_dma_rx_buff));
__HAL_UART_CLEAR_FLAG(&uart_handler, UART_FLAG_RXNE);
g_usart_info.usart_dma_rx_buff[0] = 0;
HAL_UART_Receive_DMA(&uart_handler, g_usart_info.usart_dma_rx_buff, 
USART_DMA_RECV_LEN);
}

谢谢 .

我追踪了UART_Receive_IT的功能并添加了调试代码 . 并为int a = *插入断点（huart-> pRxBuffPtr - 1）;

我发现huart-> Instance-> DR是0x31但int a是0xB1 .

我试图禁用其他中断但它仍然无法解决 .

if(huart->Init.Parity == UART_PARITY_NONE)
      {
        *huart->pRxBuffPtr++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF);
                if(*(huart->pRxBuffPtr - 1) != 0x31)
                {
                    int a = *(huart->pRxBuffPtr - 1);
                    a = a;
                }
      }
      else
      {
        *huart->pRxBuffPtr++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x007F);
      }

================================================== ======================

I found the problem point

RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 /*| RCC_CLOCKTYPE_PCLK2*/);

如果我评论 RCC_CLOCKTYPE_PCLK2 ，这个问题可以解决 . 但我不知道为什么，这是官方的示例代码 . 我认为应该是对的 .