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基于stm32的can总线彻底研究

时间:2016-11-22 15:56来源: 作者: 点击:
1、CAN总线的初始化voidcan_init(void){CAN_InitTypeDefCAN_InitStructure;CAN_FilterInitTypeDefCAN_FilterInitSt
1、CAN总线的初始化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;//禁止时间触发通信模式
CAN_InitStructure.CAN_ABOM=DISABLE;
CAN_InitStructure.CAN_AWUM=DISABLE;
CAN_InitStructure.CAN_NART=DISABLE;//CAN报文只被发送1次,不管发送的结果如何(成功、出错或仲裁丢失)
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;//选择过滤器0
CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定过滤器被设置为标识符屏蔽模式
CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//给出过滤器位宽为32位
CAN_FilterInitStructure.CAN_FilterIdHigh=slave_id<<5;//过滤器标识符
CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;//
CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0xffff;//过滤器屏蔽标识符
CAN_FilterInitStructure.CAN_FilterMaskIdLow=0xfffc;
CAN_FilterInitStructure.CAN_FilterFIFOAssignment=0;//选择FIFO0
CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;//使能过滤器
CAN_FilterInit(&CAN_FilterInitStructure);//进入初始化函数
#else
/* CAN filter init */
CAN_FilterInitStructure.CAN_FilterNumber=0;//选择过滤器0
CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定过滤器被设置为标识符屏蔽模式
CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//给出过滤器位宽为32位
CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000;//过滤器标识符
CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;//
CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0x0000;//过滤器屏蔽标识符
CAN_FilterInitStructure.CAN_FilterMaskIdLow=0x0000;
CAN_ITConfig(CAN_IT_FMP0, ENABLE);//使能指定的can中断
}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、发送程序unsignedcharCAN_PushMessage(CAN_MSG *pTransmitBuf )
{
u8 TransmitMailbox=0;
CanTxMsg TxMessage;
if(pTransmitBuf -> LEN > 8)
{
return 1;
}
/* transmit */
TxMessage.StdId=pTransmitBuf ->StdId;//用来设定标准标识符(0-0x7ff,11位)
TxMessage.ExtId=pTransmitBuf ->ExtId;
TxMessage.RTR= pTransmitBuf ->RTR;//设置RTR位为数据帧
TxMessage.IDE= pTransmitBuf ->IDE;//标识符扩展位,为标准帧
TxMessage.DLC= pTransmitBuf ->LEN;//设置数据长度
//根据DLC字段的值,将有效数据拷贝到发送数据寄存器
memcpy(TxMessage.Data, pTransmitBuf ->BUF,pTransmitBuf ->LEN);
TransmitMailbox = CAN_Transmit(&TxMessage);
// TxMessage.Data[1]=(data & 0xff00)>>8;
return 1;
}3、中断接收程序void USB_LP_CAN_RX0_IRQHandler(void)
{
//清空can接收缓存
CanRxMsg RxMessage;
RxMessage.StdId=0x00;
RxMessage.ExtId=0x00;
RxMessage.IDE=0;
RxMessage.DLC=0;
RxMessage.FMI=0;//CAN过滤主控制寄存器
memset( &RxMessage.Data[0],0,8);
//can总线接收数据函数
CAN_Receive(CAN_FIFO0, &RxMessage);
//将接收到的数据写于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))
{
//将can接收标志位置1,表示从卡应经接收到一个can报文
flag_can_recv=0;
memcpy(can_rx_data,&RxMessage.Data,RxMessage.DLC);
flag_can_recv=1;
}}4、can总线的id过滤

对扩展数据帧过滤:

本文引用地址:

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;

对标准数据帧过滤:

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;

假如要对标准远程帧进行过滤,那么:

只需要将

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总线的帧格式

数据帧格式:

远程帧格式:

6、can总线的逻辑电平

can总线的物理连接有两根线:CANH和CANL,以差分的形式输出。

(有的时候有地线,作为屏蔽线使用)

can总线的高电平3.5v,表示逻辑0

can总线的低电平1.5v,表示逻辑1

7、CAN总线的波特率计算

can时钟是RCC_APB1PeriphClock,要注意CAN时钟频率
CAN波特率=RCC_APB1PeriphClock/CAN_SJW CAN_BS1 CAN_BS2/CAN_Prescaler;
如果CAN时钟为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总线的仲裁机制

根据仲裁来判断优先级:

(1)若在同一时刻,标准格式的报文与扩展格式的报文同时抢占总线,且它们的基础ID相同,则发标准格式的报文节点就会PK成功。这是因为扩展格式在基本ID后,紧接着是SRR位,与IDE位,且这两位都是隐性位。而在标准格式中,这两位分别对应的位为RTR与r1,其中RTR既可以为隐性位,也可以为显性位,,但是r1必须为显性位。由仲裁规则可以此时标准帧必定胜出。

(2)同理,如果在同一时刻,具有相同格式,且具有相同ID的数据帧与远程帧争夺总线控制权,那么数据帧必定胜出。因为RTR显性表示数据帧,隐性表示远程帧。

stm32的can总线的配置如下: CAN_InitStructure.CAN_TTCM=DISABLE;//禁止时间触发通信模式
CAN_InitStructure.CAN_ABOM=DISABLE;
CAN_InitStructure.CAN_AWUM=DISABLE;
CAN_InitStructure.CAN_NART=DISABLE;//CAN报文只被发送1次,不管发送的结果如何(成功、出错或仲裁丢失)
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;//选择过滤器0
CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;//指定过滤器被设置为标识符屏蔽模式
CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;//给出过滤器位宽为32位下面根据设置的参数不同来决定can总线can总线的配置情况:1、对扩展数据帧进行过滤:(只接收扩展数据帧)
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:标准帧数据帧、标准远程帧和扩展远程帧均被过滤)
2、对扩展远程帧过滤:(只接收扩展远程帧)
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、对标准远程帧过滤:(只接收标准远程帧)
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、对标准数据帧过滤:(只接收标准数据帧)
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、对扩展帧进行过滤:(扩展帧不会被过滤掉)
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、对标准帧进行过滤:(标准帧不会被过滤掉)
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为要过滤的id号。
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