• Total power consumption: 4mW (less than 3% of total available power)
• Current consumption: 500uA with no sensor attached.
• Voltage drop: 50mV with Light sensor attached.
• Channel selection time: 75 ms
• Channel access logic: Random access to any channel.
• Size: 5 studs by 4 studs.
• Connector: Standard Mindstorms electric wires can be connected at the bottom or simple wire with two-pin female connectors can be connected at the top.
• Devices used: High Reliability solid state SMT and Low power Microcontroller.

#define THRESHOLD 40
task main()
{

  //AMUX is connected to port 2
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
  Wait (10);
  // set full power to motors
  SetPower(OUT_A+OUT_C,OUT_FULL);
  // drive the robot forward
  OnFwd(OUT_A+OUT_C);   
  Ch2();
// keep going forward until value of light sensor
//connected at channel2 of AMUX is <= predefined value
  while (SENSOR_2 <= THRESHOLD) {
    /* keep going */                         
    ;
  }
  Off(OUT_A+OUT_C);   // then stop
}

/* --------------------------------------
** use this function to select channel 1
** (assuming that AMUX is connected to port 2 on RCX)
** -------------------------------------- */
void Ch1(void)
{
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
}

/* --------------------------------------
** use this function to select channel 2
** -------------------------------------- */
void Ch2(void)
{
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
}

/* --------------------------------------
** use this function to select channel 3
** -------------------------------------- */
void Ch3(void)
{
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_TOUCH);
  Wait(1);
  SetSensorType(SENSOR_2,SENSOR_TYPE_LIGHT);
}

import josx.platform.rcx.*;
/**
* Simple test class for active sensor multiplexer with lejos.
* It has been tested with lejos 2.1.0 
* (should work with earlier versions since 1.4.0).
*
* @author Jean-Michel Gaudin
* @version 26-January-2004
*
* @see josx.platform.rcx.Sensor
*/

public class ActiveMpxTest implements SensorConstants
{
  // Connect the active multiplexor output to rcx input 2
  private static Sensor rcxInput = Sensor.S2;

  public static void main(String [] args)
  {
    int i; //loops
    int chValue; // active multiplexer ch values

    // select active multiplexer ch1 input
    selectCh1();
    // display ch label
    displayChlabel("ch1");
    // read and display ch1 value
    for (i=0;i<10;i++)
    {
      // read active multiplexer ch1 values
      chValue = rcxInput.readValue();
      // display it
      displayChValue(chValue);
    }

    // select active multiplexer ch2 input
    selectCh2();
    // display ch label
    displayChlabel("ch2");
    // read and display ch2 values
    for (i=0;i<10;i++)
    {
      // read active multiplexer ch2 value
      chValue = rcxInput.readValue();
      // display it
      displayChValue(chValue);
    }

    // select active multiplexer ch3 input
    selectCh3();
    // display ch label
    displayChlabel("ch3");
    // read and display ch3 value
    for (i=0;i<10;i++)
    {
      // read active multiplexer ch3 value
      chValue = rcxInput.readValue();
      // display it
      displayChValue(chValue);
    }

  }

  // Select the ch1 input of the active multiplexer
  private static void selectCh1()
  {
    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
  }

  // Select the ch2 input of the active multiplexer
  private static void selectCh2()
  {
    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
    sleep10ms();

    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
  }


  // Select the ch3 input of the active multiplexer
  private static void selectCh3()
  {
    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
    sleep10ms();

    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
    sleep10ms();

    rcxInput.passivate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_TOUCH,SENSOR_MODE_BOOL);
    sleep10ms();

    rcxInput.activate();
    rcxInput.setTypeAndMode(SENSOR_TYPE_LIGHT,SENSOR_MODE_PCT);
  }

  // Current thread sleeps for 10 ms
  private static void sleep10ms()
  {
    try {Thread.sleep(10);}
    catch(InterruptedException ie){}
  }

  // Display the ch label on the rcx LCD for 0.5 s
  private static void displayChlabel(String chLabel)
  {
    LCD.clear();
    TextLCD.print (chLabel);
    try{Thread.sleep(500);}
    catch(InterruptedException ie){}
  }

  // Display the ch value on the rcx LCD for 250 ms
  private static void displayChValue(int chValue)
  {
    LCD.clear();
    LCD.showNumber(chValue);
    try{Thread.sleep(250);}
    catch(InterruptedException ie){}
  }
}

1. Connect the multiplexer to your RCX.
2. Connect light sensor to Ch2.
3. Switch on your RCX.
4. If Light sensor is ON, reverse the polarity of RCX connection by rotating connecting wire by 180 degree.