基于can总线技术的汽车ecu设计.htm

基于CAN总线的汽车控制器ECU的设计开发实例

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style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　　从图</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">2</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中可以看出，电路主要由</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">3</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">部分组成：单片机</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">AT90CAN128</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、高速光耦</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">6N137</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和高速</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">总线收发器。单片机</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">AT90CAN128</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">主要负责传感器信息的采集、内部</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">控制器的初始化并实现数据的接收和发送等通信任务。在</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">ATA6660</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">总线的接口部分也采用了抗干扰和安全措施，</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">ATA6660</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANH</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANL</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">引脚各自通过</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">5</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">Ω的电阻与</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">总线相连，电阻可起到一定的限流作用，保护</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">ATA6660</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">免受过流冲击。</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANH</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANL</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与地之间并联两个</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">30pF</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的小电容，可以起到滤除总线上的高频干扰和一定的防电磁辐射的能力。另外，在两根</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">总线与地之间分别接了一个防雷击管，当两输入端与地之间出现瞬变干扰时，通过防雷击管的放电可以起到一定的保护作用。</SPAN><SPAN 
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size=3><SPAN lang=EN-US><FONT face="Times New Roman">3.2 </FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">软件设计</SPAN><SPAN 
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　　系统软件设计主要包括信号采集和</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">接口通信程序。利用</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">A T90CAN128</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">片上集成的</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">ADC</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">模块可以采集一些常规传感器的模拟信号，如油压、水温、气压等信号；利用定时器</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">/</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">计数器模块采集传感器脉冲信号，如转速、行驶里程信号等。对于模拟量信号，在经过放大器处理之后，可以直接控制单片机的</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">ADC</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">模块对其进行采集；对于脉冲信号，在对其进行采集时需要进行整形处理，如转速传感器获取发动机飞轮旋转时轮齿的信号，是正弦交流信号，将其整形为方波信号，利用定时器</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">/</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">计数器模块采集方波的频率来完成速度采集。为提高转速采集的实时性，通常采集脉冲信号的周期（两个脉冲信号上升沿或下降沿之间的时间）来计算其频率，并计算发动机转速，计算公式如如式（</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）所示。</SPAN><SPAN 
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　　式（</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）中</SPAN><FONT 
face="Times New Roman"> </FONT><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">为系统时钟周期，为分频系数，为发动机飞轮齿圈齿数（对于康明斯发动机为为轮齿脉冲两次上升（或下降）沿的计数器值。</SPAN><SPAN 
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　　</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">接口通信程序主要包括</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">控制器的初始化、数据接收和数据发送程序。主程序通过调用函数来实现数据的接收和发送，流程图如图</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">3</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所示，在数据接收程序中，通过查询方式读取相应消息对象中的数据。</SPAN><SPAN 
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lang=EN-US><FONT face="Times New Roman" size=3><IMG height=379 alt="" 
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left"><SPAN 
lang=EN-US><O:P><FONT face="Times New Roman" size=3></FONT></O:P></SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　　</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">控制器初始化工作主要包括波特率参数设置、接收屏蔽寄存器及接收代码寄存器的设置、使能允许寄存器的设置等。通过总线定时器寄存器</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANBT1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANBT2</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANBT3</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">来设置波特率参数。</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">AT90CAN128</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中提供了一组由</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">4</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个验收码寄存器（</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANIDT1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">～</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANIDT4</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）和</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">4</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个验收屏蔽寄存器（</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANIDM1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">～</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CANIDM4</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）组成的验收滤波器，信息只有通过它的验收滤波才能被接收；所有验收屏蔽寄存器为</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">0</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的位，验收码寄存器和</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">CAN</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">信息帧的对应位必须相同才能验收通过，而所有验收屏蔽寄存器中为</SPAN><SPAN 
lang=EN-US><FONT face="Times New Roman">1</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的位，验收码寄存器对应位的验收滤波功能则被屏蔽。通过设置验收滤波器，既可以实现节点与节点之间的点对点通信，也可以实现一点对多点的广播式通信，使整个数据通信网络更加灵活。</SPAN><SPAN 
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size=3><SPAN lang=EN-US><FONT face="Times New Roman">4</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、实