Accelerometer model element

// in the elements drag and add accelerometer element
//Accelerometer provides access to the built-in accelerometer (if present).
//Usage
//To add the Accelerometer element to your model, drag the icon element to the list of your model elements.
//The element implements the following basic methods:
//boolean isPresent(): whether the hardware includes an accelerometer
//void start(): turns the accelerometer on
//void stop(): turns the accelerometer off
//boolean isRunning(): whether reading accelerometer data has been started (using start())
//Object getDeviceData(): reads the raw data (in the device reference frame) of the acceleration measured (including gravity) and the rotation of the device. The object has x,y,z components for the acceleration, and alpha,beta,gamma for the rotation. The values are all zero if the accelerometer is not present or has not been started.
//Object getViewData(): returns a similar same object as getDeviceData(), but the acceleration is in the user's view reference frame (which has the X and Y axes horizontal and vertical on the screen and Z perpendicular to it). This function take scare of orientation changes of the screen and also differences among operating systems.
/*


//to add variables
//devicePresent set to true boolean;
//accX set to 0
//accY set to -g
//accZ set to 0
//msg set to "message"

//initialization
devicePresent=accelerometer.isPresent(); 
// to get duo usage incase no accelerometer
if (devicePresent){
  msg="Use Run button \nto access accelerometer."
   accelerometer.start();
accelerometer.setAverageInterval(0.1);
//alert("Accelerometer is detected, enjoy tilting your phone, optimised(lock) for landscape view. \nEnjoy! This toy can be used to experience effects of driving frequency (rate of tilting phone) on the spring-mass system oscillation.");
//alert("x= "+x+" , vx= "+vx);
}
else if (!devicePresent) {
  alert("Accelerometer is not present." );
  msg="Accelerometer is not present. \nUse slider to simulate tilt."
  accX=0;
  accY=-g;

}

//Evolution

  
 if (accelerometer.isPresent()||display=="block") { // if display=="block" dont take data from phone
  var viewData = accelerometer.getViewData();
  accX = viewData.x;
  accY = viewData.y;
  accZ = viewData.z;
 // console.log(accX,accY,accZ);
  //Assume sensor is not present if all componets are zero
  devicePresent=viewData.x||viewData.y||viewData.z; // need this line to avoid error
  msg=devicePresent?"":"Accelerometer not present. Use slider to simulate tilt.";

}


if (devicePresent) { // sensor active based to line 48  devicePresent=viewData.x||viewData.y||viewData.z; // need this line to avoid error
  accelerometer.start();
accelerometer.setAverageInterval(0.1);
//alert("3="+x);
  }

// put in the physics based on accelerometer data
if(devicePresent){ // sensor active based to line 48  devicePresent=viewData.x||viewData.y||viewData.z; // need this line to avoid error
theta=0; // don't use slider
  phi=-Math.atan2(accX,-accY); // new lookang for tilt to show correctly
 // phi=Math.atan2(accX,-accY); //older code wolfgang
}
else{  // sensor not active
// put in the physics of simulation model
phi=0; // angle of tilt of device
  accX=-g*Math.sin(theta);
  accY=-g*Math.cos(theta);
}

//Fixed relations
tilt=theta+phi;
if(!devicePresent ){  // no device mode
  phi=0;
  accX=-g*Math.sin(tilt);
  accY=-g*Math.cos(tilt);
 // display="block";
}