code: /**
   * Copyright (c) 2004-2005, Regents of the University of California
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   *
   * Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * Neither the name of the University of California, Los Angeles nor the
   * names of its contributors may be used to endorse or promote products
   * derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package avrora.sim.platform.sensors;
  
  import avrora.sim.FiniteStateMachine;
  import avrora.sim.mcu.*;
  
  /**
   * The <code>LightSensor</code> class implements a light sensor like that present on the Mica2.
   *
   * @author Ben L. Titzer
   */
  public class LightSensor extends Sensor {
  
      protected final AtmelMicrocontroller mcu;
      protected final int channel;
  
      protected final FiniteStateMachine fsm;
  
      protected static final String[] names = { "power down", "on" };
      protected boolean on;
      public ADC adcDevice;
  
      public LightSensor(AtmelMicrocontroller m, int adcChannel, String onPin) {
          mcu = m;
          channel = adcChannel;
          mcu.getPin(onPin).connectOutput(new OnPin());
          fsm = new FiniteStateMachine(mcu.getClockDomain().getMainClock(), 0, names, 0);
          adcDevice = (ADC)mcu.getDevice("adc");
          adcDevice.connectADCInput(new ADCInput(), channel);
      }
  
      class OnPin implements Microcontroller.Pin.Output {
          public void write(boolean val) {
              on = val;
              fsm.transition(state());
          }
      }
  
      private int state() {
          if ( !on ) return 0;
          else return 1;
      }
  
      class ADCInput implements ADC.ADCInput {
          public float getVoltage() {
              if ( data == null ) return ADC.GND_LEVEL;
              if ( !on ) return ADC.GND_LEVEL;
              int read = data.reading();
              // scale the reading back to a voltage.
              return adcDevice.getVoltageRef() * ((float)read) / 0x3ff;
          }
      }
  }
  