理解软件自带的easy工程（一）-526互联

1.数据库

有三个网络节点，两个报文，四个信号，其中EngineState报文发送两个信号：EngineSpeed，OnOff。LightState发送FlashLight，HeadLight两个信号。OnOff信号是value table型。

双击Display节点

所有信号都是它的接收信号。

2.系统变量

3..面板设计

就这么看首先Ignition控制Display的小车子变化，Speed控制车速的显示，包括转盘上的显示和车速值的显示，如果Ignition不打开，那么车速不会显示；Head和Hazard控制车灯的显示。

Control面板中Ignition与EngineStateSwitch系统变量关联，speed与EngineSpeedEntry系统变量关联，Head与HeadLight信号相关联，Hazard与HazardLightsSwitch系统变量相关联。

Display面板中小车与信号OnOff相关联，Meter1与EngineSpeedDspMeter系统变量相关联，下面的TextBox与EngineSpeed信号相关联，车前灯与系统变量LightDisplay相关联，车前灯有八种状态，如下所示

4.CAPL编码

下面是Engine代码

/*@@var:*/
variables 
{
}
/*@@end*/

/*@@sysvarChange:Engine::EngineStateSwitch:*/
on sysvar sysvar::Engine::EngineStateSwitch
{
 $EngineState::OnOff = @this;
  if(@this)
    $EngineState::EngineSpeed = @sysvar::Engine::EngineSpeedEntry;
  else
    $EngineState::EngineSpeed = 0;
}
/*@@end*/

/*@@sysvarChange:Engine::EngineSpeedEntry:*/
on sysvar sysvar::Engine::EngineSpeedEntry
{
  if(@sysvar::Engine::EngineStateSwitch) 
  {
    $EngineState::EngineSpeed = @this;
  }
}
/*@@end*/

当系统变量sysvar::Engine::EngineStateSwitch发生变化时（因为Ignition与sysvar::Engine::EngineStateSwitch相关联，所以在面板中打开Ignition时变量sysvar::Engine::EngineStateSwitch会发生变化）触发事件：

$EngineState::OnOff = @this;

将变量的值赋给信号OnOff，因为小车与OnOff绑定，所以小车状态会变化。

if(@this)
    $EngineState::EngineSpeed = @sysvar::Engine::EngineSpeedEntry;
  else
    $EngineState::EngineSpeed = 0;

如果Ignition关闭，那么变量值为0，则速度值显示为0；如果Ignition打开，则变量值会变成1，那么就会执行

$EngineState::EngineSpeed = @sysvar::Engine::EngineSpeedEntry;

将系统变量EngineSpeedEntry的值赋给信号EngineSpeed，这里Speed与变量EngineSpeedEntry相关联，所以你在control面板中拖动speed的速度条，值会变，又信号EngineSpeed与TextBox相关联，所以会显示出速度值。同时因为系统变量EngineSpeedEntry发生变化，又会触发下面的事件

on sysvar sysvar::Engine::EngineSpeedEntry
{
  if(@sysvar::Engine::EngineStateSwitch) 
  {
    $EngineState::EngineSpeed = @this;
  }
}

这里为什么要加条件，因为当发动机没开启时，即使速度条变化，也不可能有速度值，所以要先判断系统变量EngineStateSwitch值是否为1，再把速度值赋给EngineSpeed，?这里很疑惑，因为作用和上面信号触发事件中条件语句的作用一样？？？？？？？？？？？

下面是Light的脚本

/*@@var:*/
variables 
{
  msTimer tFlashLightFrequency;
  const int gFlashLightFrequency = 500;
  int gHazardLightsStatus = 0;

  int gDebugCounterTX = 0;
  int gDebugCounterTXRQ = 0;
  int gDebugCounterRX = 0;
}
/*@@end*/

/*@@startStart:Start:*/
on start
{
   setWriteDbgLevel(0); // set DbgLevel = 1 to get more information in Write-Window
}
/*@@end*/

/*@@msg:CAN1.easy::LightState (0x321):*/
on message LightState 
{
 
  if (this.dir == TX)
  {
    gDebugCounterTX++;
    if(gDebugCounterTX == 10)
    {
      writeDbgLevel(1,"LightState TX received by node %NODE_NAME%");
      gDebugCounterTX = 0;
    }     
  }
  if(this.dir == TXREQUEST)
  {
    gDebugCounterTXRQ++;
    if(gDebugCounterTXRQ == 10)
    {
      writeDbgLevel(1,"LightState TXREQUEST received by node %NODE_NAME%");
      gDebugCounterTXRQ = 0;
    } 
  }
  if (this.dir == RX)
  {
    gDebugCounterRX++;
    if(gDebugCounterRX == 10)
    {
      writeDbgLevel(1,"Error: LightState RX received by node %NODE_NAME%");
      gDebugCounterRX = 0;
    }
  }
}
/*@@end*/

/*@@timer:tFlashLightFrequency:*/
on timer tFlashLightFrequency
{
  gHazardLightsStatus = (gHazardLightsStatus == 1 ? 0 : 1);
  $LightState::FlashLight = gHazardLightsStatus;
  setTimer(this, gFlashLightFrequency);
}
/*@@end*/

/*@@key:'0':*/
on key '0'
{
  setwriteDbgLevel(0);
}
/*@@end*/

/*@@key:'1':*/
on key '1'
{
  setwriteDbgLevel(1);
}
/*@@end*/

/*@@sysvarChange:Lights::HazardLightsSwitch:*/
on sysvar sysvar::Lights::HazardLightsSwitch
{
  if (@this)
  {
    gHazardLightsStatus = 1;
    setTimer(tFlashLightFrequency, gFlashLightFrequency);
  }
  else
  {
    cancelTimer(tFlashLightFrequency);
    gHazardLightsStatus = 0;
  }

  $LightState::FlashLight = gHazardLightsStatus;
}
/*@@end*/

好长一段一段分析

on start
{
   setWriteDbgLevel(0); // set DbgLevel = 1 to get more information in Write-Window
}

这里没懂啥意思

后面的代码理解在后一篇写吧