Machine Gun Program Problems

[pegu]

I've written this program for a machine gun robot:

Code: Select all

import lejos.nxt.*;
import java.io.*;

public class MachineGun {

   public static void main(String [] args) {
   boolean safety = true; //Safety is on
   while(true) {
   TouchSensor TS = new TouchSensor(SensorPort.S1);
   Motor MA = Motor.A;   
      
      if (safety==true) {
         LCD.clear();
         LCD.drawString("Safety On", 4, 4);
         LCD.refresh();
      }
      
      if (Button.ENTER.isPressed() && safety==true) {

         safety=false;

      }
      
         if (Button.ENTER.isPressed() && safety==false) {
         
         safety=true;

      }   
      
      if (safety==false) {
         LCD.clear();
         LCD.drawString("Safety Off", 3,4);
         LCD.refresh();   
      }
      
      while (safety==false && TS.isPressed()) {
         MA.forward();
         LCD.clear();
         LCD.drawString("Firing", 5,4);
         LCD.refresh();   
         }
            
         MA.stop();
           if(Button.ESCAPE.isPressed()) {
      System.exit(0);
      }      
   }
}
   }

The safety jams occasionally. How can I fix this?

[ChrisB01]

I would try changing the order of your code:

Code: Select all

import lejos.nxt.*;
import java.io.*;

public class MachineGun {

   public static void main(String [] args) {
   boolean safety = true; //Safety is on
   TouchSensor TS = new TouchSensor(SensorPort.S1);
   Motor MA = Motor.A;   

   while(!Button.ESCAPE.isPressed) {
     
      if (Button.ENTER.isPressed() && safety==true) {

         safety=false;

      } else if (Button.ENTER.isPressed() && safety==false) {
         
         safety=true;

      }   
     
      if (safety==false && TS.isPressed()) {
         MA.forward();
         LCD.clear();
         LCD.drawString("Firing", 5,4);
         LCD.refresh();   
       } else {
           
         MA.stop();
           
      if (safety==true) {
         LCD.clear();
         LCD.drawString("Safety On", 4, 4);
         LCD.refresh();
      } else if (safety==false) {
         LCD.clear();
         LCD.drawString("Safety Off", 3,4);
         LCD.refresh();   
      }

}
   }
   }
}

I haven't tested this but I think the order now makes more sense.

Chris

[gloomyandy]

Hi,
Remember that buttons can stayed pressed for a long time (in computer terms)... so work through what will happen if the button is pressed (and stays pressed) for several iterations of your loop.... You may want to consider waiting for the button to be released once you have detected that it has been pressed....

Andy

[pegu]

@Gloomyandy I tried that but it didn't seem to help. I'm not quite sure where to put the pause.

[gloomyandy]

Hi,
It shouldn't be a pause... Once you have seen the button go down, you should set the safety on or off and then loop waiting until the button is no longer down...

Andy

[pegu]

I've decided to save my self some trouble and make the right button off and the left button on. I might do what you've suggested later, but for now this'll do. I have a question about something else though. Does the MA.forward() automatically run at full speed? If not, what is top speed for MA.setSpeed()?

[lawrie]

The default speed for a motor is 360. The top speed is about 100 times the battery voltage or 900 for a fully charged 9V battery.

[ChrisB01]

To make it pause once a button has been pressed I just add loops:

Code: Select all

import lejos.nxt.*;
import java.io.*;

public class MachineGun {

   public static void main(String [] args) {
   boolean safety = true; //Safety is on
   TouchSensor TS = new TouchSensor(SensorPort.S1);
   Motor MA = Motor.A;   

   while(!Button.ESCAPE.isPressed) {
     
      if (Button.ENTER.isPressed() && safety==true) {

         safety=false;

           while (Button.ENTER.isPressed()) {
                  // Waits until the button lifted
              }


      } else if (Button.ENTER.isPressed() && safety==false) {
         
         safety=true;

              while (Button.ENTER.isPressed()) {
                      // Waits until the button lifted
                 }

      }   
     
      if (safety==false && TS.isPressed()) {
         MA.forward();
         LCD.clear();
         LCD.drawString("Firing", 5,4);
         LCD.refresh();   
       } else {
           
         MA.stop();
           
      if (safety==true) {
         LCD.clear();
         LCD.drawString("Safety On", 4, 4);
         LCD.refresh();
      } else if (safety==false) {
         LCD.clear();
         LCD.drawString("Safety Off", 3,4);
         LCD.refresh();   
      }

}
   }
   }
}

[gloomyandy]

Yep, that would work... If you want to be nice to other threads you may want to add a Thread.yield() into the loop...

Andy