关于APM32F407配置串口DMA收发没有数据的问题记录

一.问题环境

​ 整活了一套APM32F407的板子，用了APM32F4xx_SDK_V1.4的标准外设库，正在搭建移植底层BSP框架串口部分，BSP底层配置逻辑是从STM32F407移植过来的。DMA发送时才使能通道及配置外设地址及缓存大小。

​ 串口1DMA配置过程如下：

static USART_DMAConfig_t USART_ComDmaTx(DMA_ChannelType_t channel,DMA_StreamType_t stream,uint32_t peripheralBaseAddr,uint8_t IRQChannel,uint32_t dmaFlag)
{USART_DMAConfig_t dmaConfig = {0};dmaConfig.channel = channel;dmaConfig.stream = stream;dmaConfig.dma.channel = channel;dmaConfig.dma.peripheralBaseAddr = peripheralBaseAddr;			//DMA外设地址：USART数据寄存器地址dmaConfig.dma.memoryBaseAddr = (uint32_t)0;									//内存地址，使用时再配置dmaConfig.dma.dir = DMA_DIR_MEMORYTOPERIPHERAL;									//外设地址为目的地址dmaConfig.dma.bufferSize = (uint32_t)0;										//传输时缓冲区大小，使用时再配置dmaConfig.dma.peripheralInc = DMA_PERIPHERAL_INC_DISABLE;					//外设地址固定，不递增dmaConfig.dma.memoryInc = DMA_MEMORY_INC_ENABLE;								//内存地址递增dmaConfig.dma.peripheralDataSize = DMA_PERIPHERAL_DATA_SIZE_BYTE;				//外设数据格式为字节dmaConfig.dma.memoryDataSize = DMA_MEMORY_DATA_SIZE_BYTE;						//内存数据格式为字节dmaConfig.dma.loopMode = DMA_MODE_NORMAL;										//工作在正常模式，不循环dmaConfig.dma.priority = DMA_PRIORITY_HIGH;									//DMA传输优先级为高（VeryHigh/High/Medium/Low）dmaConfig.dma.fifoMode = DMA_FIFOMODE_DISABLE;										//禁能DMA的两个Memory中变量相互访问dmaConfig.dma.peripheralBurst = DMA_PERIPHERALBURST_SINGLE;						dmaConfig.dma.fifoThreshold = DMA_FIFOTHRESHOLD_QUARTER;dmaConfig.dma.memoryBurst = DMA_MEMORYBURST_SINGLE;dmaConfig.nvic.NVIC_IRQChannel = IRQChannel;dmaConfig.nvic.NVIC_IRQChannelPreemptionPriority = 6;							//抢占优先级dmaConfig.nvic.NVIC_IRQChannelSubPriority = 0;									//响应优先级dmaConfig.nvic.NVIC_IRQChannelCmd = DISABLE;									//使能中断dmaConfig.dmaFlag = dmaFlag;return dmaConfig;
}static USART_DMAConfig_t USART_Com1DmaTx(void)
{DMA_ChannelType_t channel;DMA_StreamType_t stream;uint32_t peripheralBaseAddr;uint8_t IRQChannel;uint32_t dmaFlag;channel = DMA_CHANNEL_4;stream = DMA2_Stream7;peripheralBaseAddr = (uint32_t)(&(USART1->DATA));IRQChannel = DMA2_STR7_IRQn;dmaFlag = DMA_INT_TCIFLG7;return USART_ComDmaTx(channel,stream,peripheralBaseAddr,IRQChannel,dmaFlag);
};static void USART_DmaTxConfig(USART_t USART)
{NVIC_InitType_t		NVIC_InitStructure;/* 使能时钟 */if ((uint32_t)USART->config.dmaTx.stream > (uint32_t)DMA2){GPIO_RcmAHB1PeriphClockCmd(RCM_AHB1_PERIPH_DMA2, ENABLE);		//开启DMA时钟，用于USART发射}else{GPIO_RcmAHB1PeriphClockCmd(RCM_AHB1_PERIPH_DMA1, ENABLE);		//开启DMA时钟，用于USART发射}NVIC_InitStructure = USART->config.dmaTx.nvic;DMA_Disable(USART->config.dmaTx.stream);									//先禁止DMA通道，若之前有DMA传输，则会终止 ，必须先关闭DMA通道才能配置DMA_Reset(USART->config.dmaTx.stream);														//复位DMA1通道2的初始化DMA_Config(USART->config.dmaTx.stream,&USART->config.dmaTx.dma);		//DMA初始化if (NVIC_InitStructure.NVIC_IRQChannelCmd)  {  NVIC_EnableIRQRequest((IRQn_Type)NVIC_InitStructure.NVIC_IRQChannel,NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority,NVIC_InitStructure.NVIC_IRQChannelSubPriority);									//使能中断}  DMA_ClearStatusFlag(USART->config.dmaTx.stream,USART->config.dmaTx.dmaFlag);	//清除 全部标志DMA_EnableInterrupt(USART->config.dmaTx.stream,DMA_INT_TCIFLG);			//使能DMA通道4传输完成中断DMA_Disable(USART->config.dmaTx.stream);								//更新内存地址和传输大小之后再使能}void USART_TypeInit(USART_t USART)
{USART_Reset(USART->usart);USART_DisableDMA(USART->usart,USART_DMA_TX);USART_DisableDMA(USART->usart,USART_DMA_RX);USART_Construct(USART);USART_RccConfig(USART);USART_GpioConfig(USART);USART_Disable(USART->usart);USART_InitConfig(USART);USART_NvicConfig(USART);if (USART->config.isDmaTxEnable){USART_DmaTxConfig(USART);USART_EnableDMA(USART->usart, USART_DMA_TX);}if (USART->config.isDmaRxEnable){USART_DmaRxConfig(USART);USART_EnableDMA(USART->usart, USART_DMA_RX);}
}static void USART_SendMessage(USART_t USART, uint8_t *sendBuf, uint32_t len)
{if (USART->config.isRs485Enable){USART_Rs485TxEnable(USART);}if (USART->config.isDmaTxEnable){DMA_Disable(USART->config.dmaTx.stream);			//先禁止DMA通道，若之前有DMA传输，则会终止 ，必须先关闭DMA通道才能配置while (DMA_ReadCmdStatus(USART->config.dmaTx.stream) != DISABLE);		//确保DMA可以被设置//=======直接操作寄存器更新内存地址和传输大小-----------------------------------------------------------USART->config.dmaTx.stream->M0ADDR = (uint32_t)(sendBuf);	//更新内存地址USART->config.dmaTx.stream->NDATA = len;	//更新传输时缓冲区大小DMA_ClearStatusFlag(USART->config.dmaTx.stream,USART->config.dmaTx.dmaFlag);//清除Channel2全部标志,主要是清除传输完成标志DMA_Enable(USART->config.dmaTx.stream);//等待DMA发送结束while(DMA_ReadIntFlag(USART->config.dmaTx.stream,USART->config.dmaTx.dmaFlag) == RESET);//清除标志DMA_ClearStatusFlag(USART->config.dmaTx.stream,USART->config.dmaTx.dmaFlag);if (USART->config.isRs485Enable){USART_Rs485TxDisable(USART);}USART->send->flag = true;}
}

二.问题现象

​ 串口DMA接收和中断接收都没有问题，发送中断也没有问题。但发送配置为DMA就不能发送数据。所有串口端口配置都有这个问题，确定同样的板子刷入STM32F407的的程序也能正常使用，唯独使用APM的外设库就不行。

三.原因分析

​ 当同时使用APM32F4的DMA接收和发送时，虽然同时配置了USART_EnableDMA(USART->usart, USART_DMA_TX)和USART_EnableDMA(USART->usart, USART_DMA_RX)，但USART_EnableDMA这个函数你看他是怎么实现的：

/*!* @brief     Enables the USART DMA interface** @param     usart:   Select the USART or the UART peripheral** @param     dmaReq:  Specifies the DMA request*                     This parameter can be one of the following values:*                     @arg USART_DMA_TX    : USART DMA receive request*                     @arg USART_DMA_RX    : USART DMA transmit request*                     @arg USART_DMA_TX_RX : USART DMA transmit/receive request** @retval    None** @note      The usart can be USART1, USART2, USART3, UART4, UART5, USART6, UART7 and UART8*/
void USART_EnableDMA(USART_T* usart, USART_DMA_T dmaReq)
{usart->CTRL3_B.DMARXEN = dmaReq & 0x01;usart->CTRL3_B.DMATXEN = dmaReq >> 1;
}

是不是很明显的看出了问题所在，原来usart->CTRL3_B.DMARXEN = dmaReq & 0x01;这一句用的是直接赋值操作，而不是我们熟悉的按位或，这样当配置了USART_EnableDMA(USART->usart, USART_DMA_RX)后，原来的USART_EnableDMA(USART->usart, USART_DMA_TX);就被重置了，所以只能接收不能发送。

四.问题解决

发现问题后，对代码初始化部分进行改进，经过测试，正常收发。代码如下：

	if (USART->config.isDmaTxEnable && USART->config.isDmaRxEnable){USART_DmaTxConfig(USART);USART_DmaRxConfig(USART);USART_EnableDMA(USART->usart, USART_DMA_TX_RX);}else if (USART->config.isDmaTxEnable){USART_DmaTxConfig(USART);USART_EnableDMA(USART->usart, USART_DMA_TX);}else if (USART->config.isDmaRxEnable){USART_DmaRxConfig(USART);USART_EnableDMA(USART->usart, USART_DMA_RX);}