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            EEPW首頁 > 嵌入式系統(tǒng) > 設(shè)計(jì)應(yīng)用 > 基于stm32的can總線徹底研究

            基于stm32的can總線徹底研究

            作者: 時(shí)間:2016-11-18 來源:網(wǎng)絡(luò) 收藏
            1、CAN總線的初始化
            void can_init(void)
            {
            CAN_InitTypeDef CAN_InitStructure;
            CAN_FilterInitTypeDef CAN_FilterInitStructure;
            /* CAN register init */
            CAN_DeInit();
            CAN_StructInit(&CAN_InitStructure);

            /* CAN cell init */
            CAN_InitStructure.CAN_TTCM=DISABLE;//禁止時(shí)間觸發(fā)通信模式
            CAN_InitStructure.CAN_ABOM=DISABLE;
            CAN_InitStructure.CAN_AWUM=DISABLE;
            CAN_InitStructure.CAN_NART=DISABLE;//CAN報(bào)文只被發(fā)送1次,不管發(fā)送的結(jié)果如何(成功、出錯(cuò)或仲裁丟失)
            CAN_InitStructure.CAN_RFLM=DISABLE;
            CAN_InitStructure.CAN_TXFP=DISABLE;
            CAN_InitStructure.CAN_Mode=CAN_Mode_Normal;
            //CAN_Mode_LoopBack
            //CAN_Mode_Normal
            CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;
            CAN_InitStructure.CAN_BS1=CAN_BS1_5tq;//1--16
            CAN_InitStructure.CAN_BS2=CAN_BS2_2tq;//1--8
            CAN_InitStructure.CAN_Prescaler=2;
            CAN_Init(&CAN_InitStructure);
            #ifdef can_id_filter
            /* CAN filter init */
            CAN_FilterInitStructure.CAN_FilterNumber=0;//選擇過濾器0
            CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定過濾器被設(shè)置為標(biāo)識(shí)符屏蔽模式
            CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//給出過濾器位寬為32位
            CAN_FilterInitStructure.CAN_FilterIdHigh=slave_id<<5;//過濾器標(biāo)識(shí)符
            CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;//
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0xffff;//過濾器屏蔽標(biāo)識(shí)符
            CAN_FilterInitStructure.CAN_FilterMaskIdLow=0xfffc;
            CAN_FilterInitStructure.CAN_FilterFIFOAssignment=0;//選擇FIFO0
            CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;//使能過濾器
            CAN_FilterInit(&CAN_FilterInitStructure);//進(jìn)入初始化函數(shù)
            #else
            /* CAN filter init */
            CAN_FilterInitStructure.CAN_FilterNumber=0;//選擇過濾器0
            CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定過濾器被設(shè)置為標(biāo)識(shí)符屏蔽模式
            CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//給出過濾器位寬為32位
            CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000;//過濾器標(biāo)識(shí)符
            CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;//
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0x0000;//過濾器屏蔽標(biāo)識(shí)符
            CAN_FilterInitStructure.CAN_FilterMaskIdLow=0x0000;
            CAN_ITConfig(CAN_IT_FMP0, ENABLE);//使能指定的can中斷
            }
            void CAN_DeInit(void)
            {
            /* Enable CAN reset state */
            RCC_APB1PeriphResetCmd(RCC_APB1Periph_CAN, ENABLE);
            /* Release CAN from reset state */
            RCC_APB1PeriphResetCmd(RCC_APB1Periph_CAN, DISABLE);
            }
            2、發(fā)送程序
            unsignedcharCAN_PushMessage(CAN_MSG *pTransmitBuf )
            {
            u8 TransmitMailbox=0;
            CanTxMsg TxMessage;
            if(pTransmitBuf -> LEN > 8)
            {
            return 1;
            }
            /* transmit */
            TxMessage.StdId=pTransmitBuf ->StdId;//用來設(shè)定標(biāo)準(zhǔn)標(biāo)識(shí)符(0-0x7ff,11位)
            TxMessage.ExtId=pTransmitBuf ->ExtId;
            TxMessage.RTR= pTransmitBuf ->RTR;//設(shè)置RTR位為數(shù)據(jù)幀
            TxMessage.IDE= pTransmitBuf ->IDE;//標(biāo)識(shí)符擴(kuò)展位,為標(biāo)準(zhǔn)幀
            TxMessage.DLC= pTransmitBuf ->LEN;//設(shè)置數(shù)據(jù)長(zhǎng)度
            //根據(jù)DLC字段的值,將有效數(shù)據(jù)拷貝到發(fā)送數(shù)據(jù)寄存器
            memcpy(TxMessage.Data, pTransmitBuf ->BUF,pTransmitBuf ->LEN);
            TransmitMailbox = CAN_Transmit(&TxMessage);
            // TxMessage.Data[1]=(data & 0xff00)>>8;
            return 1;
            }
            3、中斷接收程序
            void USB_LP_CAN_RX0_IRQHandler(void)
            {
            //清空can接收緩存
            CanRxMsg RxMessage;
            RxMessage.StdId=0x00;
            RxMessage.ExtId=0x00;
            RxMessage.IDE=0;
            RxMessage.DLC=0;
            RxMessage.FMI=0;//CAN過濾主控制寄存器
            memset( &RxMessage.Data[0],0,8);
            //can總線接收數(shù)據(jù)函數(shù)
            CAN_Receive(CAN_FIFO0, &RxMessage);
            //將接收到的數(shù)據(jù)寫于modbus的寄存器1
            //modbus_regester[1]=(RxMessage.Data[0]<<8)|(RxMessage.Data[1]);
            // if((RxMessage.StdId==slave_id) && (RxMessage.ExtId==0x00) && (RxMessage.IDE==CAN_ID_STD))
            {
            //將can接收標(biāo)志位置1,表示從卡應(yīng)經(jīng)接收到一個(gè)can報(bào)文
            flag_can_recv=0;
            memcpy(can_rx_data,&RxMessage.Data,RxMessage.DLC);
            flag_can_recv=1;
            }
            }
            4、can總線的id過濾

            對(duì)擴(kuò)展數(shù)據(jù)幀過濾:

            本文引用地址:http://www.biyoush.com/article/201611/315584.htm

            CAN_FilterInitStructure.CAN_FilterNumber=0;
            CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;
            CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;
            CAN_FilterInitStructure.CAN_FilterIdHigh=(((u32)CAN_ID<<3)&0xFFFF0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow=(((u32)CAN_ID<<3)|CAN_ID_EXT|CAN_RTR_DATA)&0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow=0xFFFF;

            對(duì)標(biāo)準(zhǔn)數(shù)據(jù)幀過濾:

            CAN_FilterInitStructure.CAN_FilterIdHigh=(((u32)CAN_ID0<<21)&0xFFFF0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow=(((u32)CAN_ID0<<21)|CAN_ID_STD|CAN_RTR_DATA)&0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow=0xFFFF;

            假如要對(duì)標(biāo)準(zhǔn)遠(yuǎn)程幀進(jìn)行過濾,那么:

            只需要將

            CAN_FilterInitStructure.CAN_FilterIdLow=(((u32)CAN_ID0<<21)|CAN_ID_STD|CAN_RTR_DATA)&0xFFFF;改成:

            CAN_FilterInitStructure.CAN_FilterIdLow=(((u32)CAN_ID0<<21)|CAN_ID_STD|CAN_RTR_REMOTE)&0xFFFF;

            5、can總線的幀格式

            數(shù)據(jù)幀格式:

            遠(yuǎn)程幀格式:

            6、can總線的邏輯電平

            can總線的物理連接有兩根線:CANH和CANL,以差分的形式輸出。

            (有的時(shí)候有地線,作為屏蔽線使用)

            can總線的高電平3.5v,表示邏輯0

            can總線的低電平1.5v,表示邏輯1

            7、CAN總線的波特率計(jì)算

            can時(shí)鐘是RCC_APB1PeriphClock,要注意CAN時(shí)鐘頻率
            CAN波特率=RCC_APB1PeriphClock/CAN_SJW CAN_BS1 CAN_BS2/CAN_Prescaler;
            如果CAN時(shí)鐘為8M,CAN_SJW=1,CAN_BS1=8,CAN_BS2=7,CAN_Prescaler=2
            那么波特率就是=8M/(1 8 7)/2=250K

            8、can總線的仲裁機(jī)制

            根據(jù)仲裁來判斷優(yōu)先級(jí):

            (1)若在同一時(shí)刻,標(biāo)準(zhǔn)格式的報(bào)文與擴(kuò)展格式的報(bào)文同時(shí)搶占總線,且它們的基礎(chǔ)ID相同,則發(fā)標(biāo)準(zhǔn)格式的報(bào)文節(jié)點(diǎn)就會(huì)PK成功。這是因?yàn)閿U(kuò)展格式在基本ID后,緊接著是SRR位,與IDE位,且這兩位都是隱性位。而在標(biāo)準(zhǔn)格式中,這兩位分別對(duì)應(yīng)的位為RTR與r1,其中RTR既可以為隱性位,也可以為顯性位,,但是r1必須為顯性位。由仲裁規(guī)則可以此時(shí)標(biāo)準(zhǔn)幀必定勝出。

            (2)同理,如果在同一時(shí)刻,具有相同格式,且具有相同ID的數(shù)據(jù)幀與遠(yuǎn)程幀爭(zhēng)奪總線控制權(quán),那么數(shù)據(jù)幀必定勝出。因?yàn)镽TR顯性表示數(shù)據(jù)幀,隱性表示遠(yuǎn)程幀。

            stm32的can總線的配置如下:
            CAN_InitStructure.CAN_TTCM=DISABLE;//禁止時(shí)間觸發(fā)通信模式
            CAN_InitStructure.CAN_ABOM=DISABLE;
            CAN_InitStructure.CAN_AWUM=DISABLE;
            CAN_InitStructure.CAN_NART=DISABLE;//CAN報(bào)文只被發(fā)送1次,不管發(fā)送的結(jié)果如何(成功、出錯(cuò)或仲裁丟失)
            CAN_InitStructure.CAN_RFLM=DISABLE;
            CAN_InitStructure.CAN_TXFP=DISABLE;
            CAN_InitStructure.CAN_Mode=CAN_Mode_Normal;
            //CAN_Mode_LoopBack
            //CAN_Mode_Normal
            CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;
            CAN_InitStructure.CAN_BS1=CAN_BS1_5tq;//1--16
            CAN_InitStructure.CAN_BS2=CAN_BS2_2tq;//1--8
            CAN_InitStructure.CAN_Prescaler=2;

            CAN_Init(&CAN_InitStructure);
            /* CAN filter init */
            CAN_FilterInitStructure.CAN_FilterNumber=0;//選擇過濾器0
            CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定過濾器被設(shè)置為標(biāo)識(shí)符屏蔽模式
            CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//給出過濾器位寬為32位
            下面根據(jù)設(shè)置的參數(shù)不同來決定can總線can總線的配置情況:
            1、對(duì)擴(kuò)展數(shù)據(jù)幀進(jìn)行過濾:(只接收擴(kuò)展數(shù)據(jù)幀)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<3)&0xFFFF0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<3)|CAN_ID_EXT|CAN_RTR_DATA)&0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFF;
            (注:標(biāo)準(zhǔn)幀數(shù)據(jù)幀、標(biāo)準(zhǔn)遠(yuǎn)程幀和擴(kuò)展遠(yuǎn)程幀均被過濾)
            2、對(duì)擴(kuò)展遠(yuǎn)程幀過濾:(只接收擴(kuò)展遠(yuǎn)程幀)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<3)&0xFFFF0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<3)|CAN_ID_EXT|CAN_RTR_REMOTE)&0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFF;
            3、對(duì)標(biāo)準(zhǔn)遠(yuǎn)程幀過濾:(只接收標(biāo)準(zhǔn)遠(yuǎn)程幀)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<21)&0xffff0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<21)|CAN_ID_STD|CAN_RTR_REMOTE)&0xffff;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFF;
            4、對(duì)標(biāo)準(zhǔn)數(shù)據(jù)幀過濾:(只接收標(biāo)準(zhǔn)數(shù)據(jù)幀)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<21)&0xffff0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<21)|CAN_ID_STD|CAN_RTR_DATA)&0xffff;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFF;
            5、對(duì)擴(kuò)展幀進(jìn)行過濾:(擴(kuò)展幀不會(huì)被過濾掉)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<3)&0xFFFF0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<3)|CAN_ID_EXT)&0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFC;
            6、對(duì)標(biāo)準(zhǔn)幀進(jìn)行過濾:(標(biāo)準(zhǔn)幀不會(huì)被過濾掉)
            CAN_FilterInitStructure.CAN_FilterIdHigh = (((u32)slave_id<<21)&0xffff0000)>>16;
            CAN_FilterInitStructure.CAN_FilterIdLow = (((u32)slave_id<<21)|CAN_ID_STD)&0xffff;
            CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0xFFFF;
            CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0xFFFC;
            注:slave_id為要過濾的id號(hào)。



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