本办法使用定时器定时查询DMA接收到的数据,如果超过设定的周期则认为本次数据包结束,将数据拷贝到缓冲区,交由其他程序处理。可以接收任意大小的数据包,尤其适用于MODBUS等协议,曾经用于GPS、GPRS等接收,很实用。本方法占用CPU时间极少,尤其是波特率很高时,效果更加明显。
当某一个串口的数据接收超时以后,定时器中断中将数据拷贝到缓冲区,在主程序中可以判断数据标志UART1_Flag,大于0的时候即代表有数据接收到,可以处理,处理完后将此变量清零即可。
两个数据包间隔较小时,可以将定时器的周期调短些。
//超时时间定义 #define UART1_TimeoutComp 2 //20ms #define UART2_TimeoutComp 10 //100ms #define UART3_TimeoutComp 10 //100ms #define SRC_USART1_DR (&(USART1->DR)) //串口接收寄存器作为源头 #define SRC_USART2_DR (&(USART2->DR)) //串口接收寄存器作为源头 #define SRC_USART3_DR (&(USART3->DR)) //串口接收寄存器作为源头 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; //定时器初始化 void TimerInit( void ) { //定时器初始化数据结构定义 TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; //初始化定时器,用于超时接收,20ms //复位计数器 TIM_DeInit( TIM2 ); TIM_TimeBaseStructure.TIM_Period = 100; //计数上限,100*100us = 10000us = 10ms TIM_TimeBaseStructure.TIM_Prescaler = 4799; //预分频4800,48MHz主频,分频后时钟周期100us TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //不分频 TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //向上计数 TIM_TimeBaseStructure.TIM_RepetitionCounter = 0; //初始化 TIM_TimeBaseInit( TIM2, &TIM_TimeBaseStructure ); //清中断 TIM_ClearFlag( TIM2, TIM_FLAG_Update ); //使能定时器中断 TIM_ITConfig( TIM2, TIM_IT_Update, ENABLE ); TIM_UpdateDisableConfig( TIM2, DISABLE ); //定时器清零 TIM_SetCounter( TIM2, 0 ); //定时器启动 TIM_Cmd( TIM2, ENABLE ); } //DMA初始化,只列出一个通道,其他两个通道相同 void DMA5_Init( void ) { DMA_InitTypeDef DMA_InitStructure; DMA_DeInit( DMA1_Channel5 ); //将DMA的通道1寄存器重设为缺省值 DMA_InitStructure.DMA_PeripheralBaseAddr = ( u32 )SRC_USART1_DR; //源头BUF既是 (&(USART1->DR)) DMA_InitStructure.DMA_MemoryBaseAddr = ( u32 )uart1_data_temp; //目标BUF 既是要写在哪个个数组之中 DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; //外设作源头//外设是作为数据传输的目的地还是来源 DMA_InitStructure.DMA_BufferSize = 200; //DMA缓存的大小 单位在下边设定 DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外设地址寄存器不递增 DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //内存地址递增 DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外设字节为单位 DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte; //内存字节为单位 DMA_InitStructure.DMA_Mode = DMA_Mode_Circular; //工作在循环缓存模式 DMA_InitStructure.DMA_Priority = DMA_Priority_High; //4优先级之一的(高优先)VeryHigh/High/Medium/Low DMA_InitStructure.DMA_M2M = DMA_M2M_Disable; //非内存到内存 DMA_Init( DMA1_Channel5, &DMA_InitStructure ); //根据DMA_InitStruct中指定的参数初始化DMA的通道1寄存器 DMA_ITConfig( DMA1_Channel5, DMA_IT_TC, ENABLE ); //DMA5传输完成中断 USART_DMACmd( USART1, USART_DMAReq_Rx, ENABLE ); //使能USART1的接收DMA请求 DMA_Cmd( DMA1_Channel5, ENABLE ); //正式允许DMA } //串口初始化,只列出一个通道,其他两个通道相同 void USART1_Configuration( void ) { //串口初始化数据结构定义 USART_InitTypeDef USART_InitStructure; //初始化串口为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 ); //启动串口,不需要接收中断 USART_Cmd( USART1, ENABLE ); //默认设置为输入状态 DMA5_Init(); } //定时器中断服务程序 void TIM2_IRQHandler( void ) { u16 i; //清定时器中断 TIM_ClearITPendingBit( TIM2, TIM_FLAG_Update ); UART1_Timeout++; UART2_Timeout++; UART3_Timeout++; //------------------------------------------------------------------ i = DMA_GetCurrDataCounter( DMA1_Channel5 ); DMA_ClearITPendingBit( DMA1_IT_GL5 ); //清除全部中断标志 if ( i != uart1_Flag_last ) //未完成传输 { UART1_Timeout = 0; uart1_Flag_last = i; } else { if ( UART1_Timeout > UART1_TimeoutComp ) //产生超时 { if ( i < 200 ) //有数据接收到 { UART1_FlagTemp = 200-i; //得到接收到的字节数 for ( i = 0; i < UART1_FlagTemp; i++ ) //将数据拷贝到缓冲区 uart1_data[ i ] = uart1_data_temp[ i ]; UART1_Flag = UART1_FlagTemp; DMA_ClearFlag( DMA1_FLAG_TC5 ); DMA_Cmd( DMA1_Channel5, DISABLE ); //正式允许DMA DMA5_Init(); } UART1_Timeout = 0; } } //------------------------------------------------------------------ i = DMA_GetCurrDataCounter( DMA1_Channel6 ); DMA_ClearITPendingBit( DMA1_IT_GL6 ); //清除全部中断标志 if ( i != uart2_Flag_last ) //未完成传输 { UART2_Timeout = 0; uart2_Flag_last = i; } else { if ( UART2_Timeout > UART2_TimeoutComp ) //产生超时 { if ( i < 500 ) //有数据接收到 { UART2_FlagTemp = 500-i; //得到接收到的字节数 for ( i = 0; i < UART2_FlagTemp; i++ ) //将数据拷贝到缓冲区 uart2_data[ i ] = uart2_data_temp[ i ]; UART2_Flag = UART2_FlagTemp; DMA_ClearFlag( DMA1_FLAG_TC6 ); DMA_Cmd( DMA1_Channel6, DISABLE ); //正式允许DMA DMA6_Init(); } UART2_Timeout = 0; } } //------------------------------------------------------------------ i = DMA_GetCurrDataCounter( DMA1_Channel3 ); DMA_ClearITPendingBit( DMA1_IT_GL3 ); //清除全部中断标志 if ( i != uart3_Flag_last ) //未完成传输 { UART3_Timeout = 0; uart3_Flag_last = i; } else { if ( UART3_Timeout > UART3_TimeoutComp ) //产生超时 { if ( i < 500 ) //有数据接收到 { UART3_FlagTemp = 500-i; //得到接收到的字节数 for ( i = 0; i < UART3_FlagTemp; i++ ) //将数据拷贝到缓冲区 uart3_data[ i ] = uart3_data_temp[ i ]; UART3_Flag = UART3_FlagTemp; DMA_ClearFlag( DMA1_FLAG_TC3 ); DMA_Cmd( DMA1_Channel3, DISABLE ); //正式允许DMA DMA3_Init(); } UART3_Timeout = 0; } } }
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