情况如下：
1 第一次调用USART1_SendDMA时无法进入中断，但后续却可以；
2 没有输出
代码如下：
串口配置：
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1 , ENABLE);
DMA_DeInit(DMA1_Stream0);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;//
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin =GPIO_Pin_10;// GPIO_PinSource10;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_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_Tx;
USART_Init(USART1, &USART_InitStructure);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_3);
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream0_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
DMA_ITConfig(DMA1_Stream0,DMA_IT_TC,ENABLE);
USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
USART_Cmd(USART1, ENABLE);
输出函数：
void USART1_SendDMA(char* buf,int len)
{
DMA_InitTypeDef DMA_InitStruct;
DMA_Cmd(DMA1_Stream0,DISABLE);
DMA_ClearITPendingBit(DMA1_Stream0, DMA_IT_TCIF0);
DMA_InitStruct.DMA_Channel = DMA_Channel_0;
DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)(&USART1->DR);
DMA_InitStruct.DMA_Memory0BaseAddr = (uint32_t)buf;
DMA_InitStruct.DMA_DIR = DMA_DIR_MemoryToPeripheral;
DMA_InitStruct.DMA_BufferSize = len;
DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStruct.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStruct.DMA_Mode = DMA_Mode_Normal;
DMA_InitStruct.DMA_Priority = DMA_Priority_Medium;
DMA_InitStruct.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStruct.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStruct.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_InitStruct.DMA_FIFOThreshold = DMA_FIFOThreshold_1QuarterFull;
DMA_Init(DMA1_Stream0,&DMA_InitStruct);
DMA_Cmd(DMA1_Stream0,ENABLE);
中断：
void DMA1_Stream0_IRQHandler()
{
if(DMA_GetITStatus(DMA1_Stream0, DMA_IT_TCIF0))
{
//TODO:Add code here
DMA_ClearITPendingBit(DMA1_Stream0, DMA_IT_TCIF0);
DMA_Cmd(DMA1_Stream0,DISABLE);
}
}
DEBUG时候发现USART1_SendDMA输入的buf内容正确，比如输入一个"TEST"，可以在DEBUG时候看到buf里面对应的内容，len此时为4 |
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