欢迎进入IT技术社区论坛，与200万技术人员互动交流 >>进入 主节点的请求帧在D1中给出需要分配帧ID的第一个帧在帧数组中的序号，一般来说，从节点所用到的所有帧的ID会被排列成一个帧数组。如果要分配帧ID，则通过D2到D5给出新的帧ID；如果要禁止某个帧，则将
欢迎进入IT技术社区论坛，与200万技术人员互动交流 >>进入
主节点的请求帧在D1中给出需要分配帧ID的第一个帧在帧数组中的序号，一般来说，从节点所用到的所有帧的ID会被排列成一个帧数组。如果要分配帧ID，则通过D2到D5给出新的帧ID；如果要禁止某个帧，则将这个帧对应的PID设为0x00；如果要继续使用现在的帧ID，则将这个帧对应的PID设为0xFF.（5）读取从节点信息读取节点信息根据D1中ID的值，可以读取不同的从节点信息。目前，只规定了ID为0和ID为1的情况，其他可保留或由用户自己确定。
3 LIN通信的实现
3.1 TLE9832的LIN模块
TLE9832是一款由英飞凌公司生产的8位功率级单片机，专门用于车窗控制。其中的LIN总线模块支持LIN2.1和LIN2.0，并向下兼容LIN 1.3.该模块可以工作在普通模式、接收模式和禁止模式下。各个模式的特点如表1所列。
其中，普通模式又可根据传输速率的大小分为低速模式、中速模式、高速模式和Flash模式。低速模式的最大传输速率为10.4 kbps；中速模式是普通的LIN传输模式，最大传输速率为20 kbps；高速模式的最大传输速率为40 kbps；Flash模式的最大传输速率为11 5 khps.为了避免打断传输过程，在普通模式下禁止改变传输速率。正确的做法是先禁止发送功能，再改变传输速率，最后允许发送功能。
LIN模块在普通模式下还建立了一种自动省电机制。当发送队列中没有数据时，将自动禁止发送功能；当有发送请求时，将自动开启发送功能。
3.2基于TLE9832的车窗防夹控制系统
基丁TLE9832的防夹车窗控制系统是英飞凌-同济微控制器与嵌入式系统实验室的最新研究成果。用户可以通过按键或者LIN总线控制车窗的上升和下降。基于TLE9832的防夹车窗系统原理图如图4所示。可通过控制PWM信号控制电机的转速，而霍尔传感器TLE4966又会采集电机的转速并传送给TLE9832，这样就构成了闭环控制。此外，电机的电枢电流在转化为电压信号后，被传送给TLE9832的ADC模块。如果车窗在上升过程中遇到不正常的阻力，电枢电流和电机转速都会发生异常的变化，TLE9832可以根据这种变化判断是否执行防夹算法，避免伤害乘客。
3.3 LIN通信部分的软件设计
LIN通信部分的程序流程如图5所示。可将车窗控制器中LIN通信部分的程序分为两个部分：①第一部分为初始化，在每次重新上电后，程序都会首先读取Flash中的数据，若0x8000中的数据为0x78，则判断产品在出厂后执行过保存配置的功能。所以程序会将存储在Flash中的NAD和帧ID读出来，作为当前的NAD和帧ID.接着是初始化LIN模块，包括设置与LIN通信相关的定时器和UART等外设，设置从节点的各个参数、波特率等。
②第二部分则放在定时器中断里面，在每次中断时进行节点配置、数据的发送和接收。首先是根据帧ID判断有无节点配置任务，若有则根据SID执行各种节点配置任务；接着根据收到的数据帧内容控制车窗的自动上升和自动下降；最后将车窗信息，包括电枢电流、车窗位置等发给主节点。
4 LIN通信的测试结果
本测试借助Kvaser公司出品的LIN通信测试工具Lcaf Professional LIN及其配套软件CANLab完成。测试时测试工具设置为主节点，TLE9 832单片机设置为从节点，比特率设置为19200 bps.初始NAD设置为0x06，初始帧ID为无条件帧0x00、0x01和诊断配置帧0x3C、0x3D，Suppli erID和Function ID都为0x0000.首先测试节点配置的各个功能：先测试分配NAD功能，将NAD修改为0x03；接着测试有条件分配NAD功能，将NAD修改为0x08；然后测试分配一系列帧ID功能，并保存设置；最后重新上电，并读取从节点信息。节点配置功能的测试结果如图6所示。
然后通过LIN总线控制车窗自动上升和下降，测试结果如图7所示。
最后通过LIN总线获得车窗上升过程中电枢电流的数据，并转换成图形，如图8所示。其中电流值为经过A/D转换后的结果。
结语
本文基于LIN2.1协议设计了防夹车窗控制系统中的通信模块。可以看出，该模块可以很好地满足用户在数据传输和诊断等方面的需求。LIN总线自身的发展必将推动车身控制领域的进一步发展。
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