STM32串口+DMA使用
STM32有5个串口资源（USART1，USART2，USART3及UART4，UART5）。其中3个USART（通用同步/异步收/发器universalsynchronous asynchronous receiver and transmitter）；2个UART（通用异步收/发器universalasynchronous receiver and transmitter）；至于USART与UART的区别，如果只是拿来做串口用，没什么区别，在车载项目里，我们拿来做串口用，USART与UART在编程上并没有区别。
其中USART1，USART2，USART3，UART4支持DMA方式，UART5不支持DMA。(详见数据手册stm32f105&107_datesheet_English的P18/2.3.17)。
DMA（Derect MemoryAcess直接存储器存取），STM32有2个DMA，DMA1有7个通道，DMA2有5和通道，每个通道对应不同的外设（详见数据手册P272/13.3.7）。
1.时钟RCC配置：
串口时钟 + DMA时钟 + IO时钟
static void RCC_Configuration(void)
{
RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4,ENABLE); //串口时钟
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2,ENABLE); //DMA2时钟
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC| RCC_APB2Periph_AFIO, ENABLE);//IO时钟
}
2.GPIO配置：
UART4的TX为PC10脚，发送端配置为复用推挽输出模式（GPIO_Mode_AF_PP）
UART4的RX为PC11脚，接收端配置为浮空输入模式（GPIO_Mode_IN_FLOATING）
static void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin =GPIO_Pin_10;
GPIO_InitStructure.GPIO_Mode =GPIO_Mode_AF_PP; //TX复用推挽输出模式
GPIO_InitStructure.GPIO_Speed =GPIO_Speed_50MHz;
GPIO_Init(GPIOC,&GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin =GPIO_Pin_11;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //RX浮空输入模式
GPIO_InitStructure.GPIO_Speed =GPIO_Speed_50MHz;
GPIO_Init(GPIOC,&GPIO_InitStructure);
}
3.中断NVIC配置：
配置两个DMA通道中断：
UART4的RX的DMA通道为DMA2的通道3；
UART4的TX的DMA通道为DMA2的通道5；
static void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel =UART4_IRQn;//串口中断
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority= 0;
NVIC_InitStructure.NVIC_IRQChannelCmd =ENABLE;
NVIC_Init(&NVIC_InitStructure);
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Channel3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd =ENABLE;
NVIC_Init(&NVIC_InitStructure);
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Channel5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd= ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
4.串口配置：
即填充串口配置结构体
static void UART4_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
USART_InitStructure.USART_BaudRate =115200;
USART_InitStructure.USART_WordLength =USART_WordLength_8b;//数据位8位
USART_InitStructure.USART_StopBits =USART_StopBits_1;//停止位1位
USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位
USART_InitStructure.USART_HardwareFlowControl= USART_HardwareFlowControl_None;//不采用硬件流控
USART_InitStructure.USART_Mode =USART_Mode_Rx | USART_Mode_Tx;//TX、RX都开启
USART_Init(UART4,&USART_InitStructure);
USART_Cmd(UART4, ENABLE); //使能UART4外设
}
5.DMA配置：
DMA可以把数据从外设转移到内存（如串口接收的时候），也可以从内存转移到外设（如串口发送的时候）；不同方向的数据转移要各做相应的配置
串口接收：
void UART4_Start_DMA_Recv(void * recvBuf, uint32_t bufLen)
{
DMA_InitTypeDef DMA_InitStructure;
UART4_Configuration();
/* DMA1 Channel5 (triggered by USART1 Rxevent) Config */
DMA_InitStructure.DMA_PeripheralBaseAddr =(u32)&(UART4->DR);//外设基地址，串口4数据寄存器
DMA_InitStructure.DMA_MemoryBaseAddr =(u32)recvBuf;//内存基地址，数组UART4_DMA_HeadBuf
DMA_InitStructure.DMA_DIR =DMA_DIR_PeripheralSRC;//SRC外设到内存
DMA_InitStructure.DMA_BufferSize =bufLen;//DMA数据传输长度
DMA_InitStructure.DMA_PeripheralInc =DMA_PeripheralInc_Disable;//外设地址不自增
DMA_InitStructure.DMA_MemoryInc =DMA_MemoryInc_Enable;//内存地址自增
DMA_InitStructure.DMA_PeripheralDataSize =DMA_PeripheralDataSize_Byte;//外设数据单位为1字节
DMA_InitStructure.DMA_MemoryDataSize =DMA_MemoryDataSize_Byte;//内存数据单位为1字节
DMA_InitStructure.DMA_Mode =DMA_Mode_Normal;//DMA传输数据模式，正常模式，传一轮
DMA_InitStructure.DMA_Priority =DMA_Priority_High;//DMA通道优先级
DMA_InitStructure.DMA_M2M =DMA_M2M_Disable;//禁止DMA内存到内存传输
DMA_DeInit(DMA2_Channel3);//UART4的RX为DMA2通道3
DMA_Init(DMA2_Channel3,&DMA_InitStructure);
DMA_ITConfig(DMA2_Channel3, DMA_IT_TC,ENABLE);//配置DMA2发送完成后产生中断
USART_DMACmd(UART4, USART_DMAReq_Rx,ENABLE);//配置串口向DMA发出Tx请求，请求传输数据
DMA_Cmd(DMA2_Channel3, ENABLE);//正式开启DMA
}
串口发送：
void UART4_Start_DMA_Send(void * sendBuf, uint32_t bufLen)
{
DMA_InitTypeDefDMA_InitStructure;
if (bufLen == 0)
return ;
memcpy(UART4_DMA_SendBuf, sendBuf, bufLen);
DMA_InitStructure.DMA_PeripheralBaseAddr =(u32)(&UART4->DR);//外设基地址，串口4数据寄存器
DMA_InitStructure.DMA_MemoryBaseAddr =(uint32_t)UART4_DMA_SendBuf;
DMA_InitStructure.DMA_DIR =DMA_DIR_PeripheralDST;//DST内存到外设
DMA_InitStructure.DMA_BufferSize =bufLen;
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_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_Mode =DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority =DMA_Priority_High;
DMA_InitStructure.DMA_M2M =DMA_M2M_Disable;
DMA_DeInit(DMA2_Channel5); //UART4的TX为DMA2通道5
DMA_Init(DMA2_Channel5,&DMA_InitStructure);
DMA_ITConfig(DMA2_Channel5, DMA_IT_TC,ENABLE);//配置DMA2发送完成后产生中断
USART_DMACmd(UART4,USART_DMAReq_Tx,ENABLE);//配置串口向DMA发出Tx请求，请求传输数据
DMA_Cmd(DMA2_Channel5, ENABLE);//正式开启DMA
gDMA2Channel5Running = true;
}
6.DMA中断函数：
串口接收或发送的时候，DMA数据传输完成后会产生中断，在相应中断函数编写代码(注意中断函数名一定要与启动文件中断向量表一致)
DMA串口接收完成中断：
void DMA2_Channel3_IRQHandler(void)//接收完成中断
{
OSIntEnter();//ucos进入中断服务函数
if(DMA_GetITStatus(DMA2_IT_TC3))
{
//获取剩余长度，一般都为0，调试用
DMA_ClearITPendingBit(DMA2_IT_GL3); //清除全部中断标志
DMA_Cmd(DMA2_Channel3, DISABLE);
if(0 == DMAReciveState)
{
if(HOST_MSG_START_CODE_FIRST_BYTE== UART4_DMA_HeadBuf[0])//比较读取的第1个字节FF
{
DMAReciveState = 1;
UART4_Start_DMA_Recv((void*)(UART4_DMA_HeadBuf + 1), 3);//再读取后3个字节FFFFFF
}
else
{
UART4_Start_DMA_Recv((void*)UART4_DMA_HeadBuf, 1);
}
}
else if(1 == DMAReciveState)
{
if(HOST_MSG_START_CODE ==*(uint32_t *)UART4_DMA_HeadBuf)//比较整个起始码FFFFFFFF
{
DMAReciveState = 2;
UART4_Start_DMA_Recv((void*)(UART4_DMA_HeadBuf + 4), 8);//再读取后8个字节（cmdtype+bodylen）
}
else
{
DMAReciveState = 0;
memset(UART4_DMA_HeadBuf, 0, sizeof(UART4_DMA_HeadBuf));
UART4_Start_DMA_Recv((void*)UART4_DMA_HeadBuf, 1);
}
}
else if(2 == DMAReciveState)
{
HOST_MSG_HEADER_T *pMCUMsgHeader;
DMAReciveState = 3;
pMsgBuffer = (uint8_t*)GetPhoneRecvBuf();//申请一个PhoneRecvBuf接收内存块
if(pMsgBuffer == NULL)
{
DMAReciveState = 0;
memset(UART4_DMA_HeadBuf, 0,sizeof(UART4_DMA_HeadBuf));
UART4_Start_DMA_Recv((void*)UART4_DMA_HeadBuf, 1);
OSIntExit(); //means get out of the inturrept!
return;
}
memcpy(pMsgBuffer,UART4_DMA_HeadBuf, sizeof(HOST_MSG_HEADER_T));//把数组数据（startcode+cmdtype+bodylen）拷贝到内存块
pMCUMsgHeader = (HOST_MSG_HEADER_T*)pMsgBuffer;//指针类型转换
UART4_Start_DMA_Recv((void*)(pMsgBuffer +sizeof(HOST_MSG_HEADER_T)), pMCUMsgHeader->bodyLen + CRC_LEN);//再读取后面数据（data+crc）到内存块
}
else if(3 == DMAReciveState)
{
DMAReciveState = 0;
memset(UART4_DMA_HeadBuf, 0,sizeof(UART4_DMA_HeadBuf));
UART4_Start_DMA_Recv((void*)UART4_DMA_HeadBuf, 1);//此处再读1个字节（起始码第1个字节FF），开始下一轮接收数据
if (pMsgBuffer != NULL)
{
PutMsg2PhoneRecvQueue(pMsgBuffer);//把PhoneRecvBuf接收内存块指针发送到PhoneRecvQ接收消息队列
pMsgBuffer = NULL;
}
}
}
OSIntExit();//ucos退出中断服务函数
}
DMA串口发送完成中断：
void DMA2_Channel5_IRQHandler(void)//发送完成中断
{
OSIntEnter();
if(DMA_GetITStatus(DMA2_IT_TC5)==SET)
{
DMA_ClearFlag(DMA2_IT_GL5);
DMA_Cmd(DMA2_Channel5,DISABLE);
gDMA2Channel5Running = false;
}
OSIntExit();
}
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附：
DMA常用库函数：
