STM32串口DMA超時(shí)接收方法，可大大節(jié)約CPU時(shí)間

本辦法使用定時(shí)器定時(shí)查詢DMA接收到的數(shù)據(jù)，如果超過(guò)設(shè)定的周期則認(rèn)為本次數(shù)據(jù)包結(jié)束，將數(shù)據(jù)拷貝到緩沖區(qū)，交由其他程序處理?？梢越邮杖我獯笮〉臄?shù)據(jù)包，尤其適用于MODBUS等協(xié)議，曾經(jīng)用于GPS、GPRS等接收，很實(shí)用。本方法占用CPU時(shí)間極少，尤其是波特率很高時(shí)，效果更加明顯。
當(dāng)某一個(gè)串口的數(shù)據(jù)接收超時(shí)以后，定時(shí)器中斷中將數(shù)據(jù)拷貝到緩沖區(qū)，在主程序中可以判斷數(shù)據(jù)標(biāo)志UART1_Flag，大于0的時(shí)候即代表有數(shù)據(jù)接收到，可以處理，處理完后將此變量清零即可。
兩個(gè)數(shù)據(jù)包間隔較小時(shí)，可以將定時(shí)器的周期調(diào)短些。

//超時(shí)時(shí)間定義
#define UART1_TimeoutComp 2//20ms
#define UART2_TimeoutComp 10//100ms
#define UART3_TimeoutComp 10//100ms

#define SRC_USART1_DR (&(USART1->DR)) //串口接收寄存器作為源頭
#define SRC_USART2_DR (&(USART2->DR)) //串口接收寄存器作為源頭
#define SRC_USART3_DR (&(USART3->DR)) //串口接收寄存器作為源頭


extern u16 UART1_Flag,UART2_Flag,UART3_Flag;
extern u8 uart1_data[200],uart3_data[500],uart2_data[500];

u8 UART1_Timeout,UART2_Timeout,UART3_Timeout;
u16 UART1_FlagTemp,UART2_FlagTemp,UART3_FlagTemp;
u8 uart1_data_temp[200],uart2_data_temp[500],uart3_data_temp[500];

u16 uart1_Flag_last=0,uart2_Flag_last=0,uart3_Flag_last=0;

//定時(shí)器初始化
void TimerInit(void)
{
//定時(shí)器初始化數(shù)據(jù)結(jié)構(gòu)定義
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
//初始化定時(shí)器，用于超時(shí)接收，20ms

//復(fù)位計(jì)數(shù)器
TIM_DeInit(TIM2);

TIM_TimeBaseStructure.TIM_Period = 100; //計(jì)數(shù)上限，100*100us = 10000us = 10ms
TIM_TimeBaseStructure.TIM_Prescaler = 4799; //預(yù)分頻4800,48MHz主頻，分頻后時(shí)鐘周期100us
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;//不分頻
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上計(jì)數(shù)
TIM_TimeBaseStructure.TIM_RepetitionCounter=0;
//初始化
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);

//清中斷
TIM_ClearFlag(TIM2, TIM_FLAG_Update);


//使能定時(shí)器中斷
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);
TIM_UpdateDisableConfig(TIM2,DISABLE);
//定時(shí)器清零
TIM_SetCounter(TIM2,0);
//定時(shí)器啟動(dòng)
TIM_Cmd(TIM2,ENABLE);
}


//DMA初始化，只列出一個(gè)通道，其他兩個(gè)通道相同
void DMA5_Init(void)
{
DMA_InitTypeDef DMA_InitStructure;

DMA_DeInit(DMA1_Channel5); //將DMA的通道1寄存器重設(shè)為缺省值
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)SRC_USART1_DR; //源頭BUF既是 (&(USART1->DR))
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)uart1_data_temp; //目標(biāo)BUF 既是要寫(xiě)在哪個(gè)個(gè)數(shù)組之中
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; //外設(shè)作源頭//外設(shè)是作為數(shù)據(jù)傳輸?shù)哪康牡剡€是來(lái)源
DMA_InitStructure.DMA_BufferSize = 200; //DMA緩存的大小 單位在下邊設(shè)定
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設(shè)地址寄存器不遞增
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //內(nèi)存地址遞增
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外設(shè)字節(jié)為單位
DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte; //內(nèi)存字節(jié)為單位
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular; //工作在循環(huán)緩存模式
DMA_InitStructure.DMA_Priority = DMA_Priority_High; //4優(yōu)先級(jí)之一的(高優(yōu)先)VeryHigh/High/Medium/Low
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable; //非內(nèi)存到內(nèi)存
DMA_Init(DMA1_Channel5, &DMA_InitStructure); //根據(jù)DMA_InitStruct中指定的參數(shù)初始化DMA的通道1寄存器
DMA_ITConfig(DMA1_Channel5, DMA_IT_TC, ENABLE); //DMA5傳輸完成中斷
USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE); //使能USART1的接收DMA請(qǐng)求

DMA_Cmd(DMA1_Channel5, ENABLE); //正式允許DMA
}

//串口初始化，只列出一個(gè)通道，其他兩個(gè)通道相同
void USART1_Configuration(void)
{
//串口初始化數(shù)據(jù)結(jié)構(gòu)定義
USART_InitTypeDef USART_InitStructure;

//初始化串口為38400,n,8,1
USART_InitStructure.USART_BaudRate = 38400;
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;
//初始化
USART_Init(USART1, &USART_InitStructure);

//啟動(dòng)串口，不需要接收中斷
USART_Cmd(USART1, ENABLE);

//默認(rèn)設(shè)置為輸入狀態(tài)
DMA5_Init();
}

//定時(shí)器中斷服務(wù)程序
void TIM2_IRQHandler(void)
{
u16 i;
//清定時(shí)器中斷
TIM_ClearITPendingBit(TIM2, TIM_FLAG_Update);

UART1_Timeout++;
UART2_Timeout++;
UART3_Timeout++;
//------------------------------------------------------------------
i=DMA_GetCurrDataCounter(DMA1_Channel5);
DMA_ClearITPendingBit(DMA1_IT_GL5); //清除全部中斷標(biāo)志

if(i!=uart1_Flag_last)//未完成傳輸
{
UART1_Timeout=0;
uart1_Flag_last=i;
}
else
{
if(UART1_Timeout>UART1_TimeoutComp)//產(chǎn)生超時(shí)
{
if(i<200) //有數(shù)據(jù)接收到
{
UART1_FlagTemp=200-i; //得到接收到的字節(jié)數(shù)

for(i=0;i uart1_data[i]=uart1_data_temp[i];
UART1_Flag=UART1_FlagTemp;

DMA_ClearFlag(DMA1_FLAG_TC5);
DMA_Cmd(DMA1_Channel5, DISABLE); //正式允許DMA
DMA5_Init();
}
UART1_Timeout=0;
}
}
//------------------------------------------------------------------
i=DMA_GetCurrDataCounter(DMA1_Channel6);
DMA_ClearITPendingBit(DMA1_IT_GL6); //清除全部中斷標(biāo)志

if(i!=uart2_Flag_last)//未完成傳輸
{
UART2_Timeout=0;
uart2_Flag_last=i;
}
else
{
if(UART2_Timeout>UART2_TimeoutComp)//產(chǎn)生超時(shí)
{
if(i<500) //有數(shù)據(jù)接收到
{
UART2_FlagTemp=500-i;//得到接收到的字節(jié)數(shù)

for(i=0;i uart2_data[i]=uart2_data_temp[i];
UART2_Flag=UART2_FlagTemp;

DMA_ClearFlag(DMA1_FLAG_TC6);
DMA_Cmd(DMA1_Channel6, DISABLE); //正式允許DMA
DMA6_Init();

}
UART2_Timeout=0;
}
}
//------------------------------------------------------------------
i=DMA_GetCurrDataCounter(DMA1_Channel3);
DMA_ClearITPendingBit(DMA1_IT_GL3); //清除全部中斷標(biāo)志

if(i!=uart3_Flag_last)//未完成傳輸
{
UART3_Timeout=0;
uart3_Flag_last=i;
}
else
{
if(UART3_Timeout>UART3_TimeoutComp)//產(chǎn)生超時(shí)
{
if(i<500) //有數(shù)據(jù)接收到
{
UART3_FlagTemp=500-i;//得到接收到的字節(jié)數(shù)

for(i=0;i uart3_data[i]=uart3_data_temp[i];
UART3_Flag=UART3_FlagTemp;

DMA_ClearFlag(DMA1_FLAG_TC3);
DMA_Cmd(DMA1_Channel3, DISABLE); //正式允許DMA
DMA3_Init();

}
UART3_Timeout=0;
}
}
}