Question

I am new to java and lejos so please don’t blame me if i’m asking rather dumb questions.

I was trying to let the lego ultrasonic sensor scan a 360 degree area around my nxt by rotating it on a motor. Every 5 degrees it saves the distance to a .txt file.

My problem is that later when I read the file from my PC after uploading it with nxjbrowse.bat, it only contains the ASCII characters linked to the numbers that supposed to be saved there (0 – 255).

My code for the NXT:

package Dataloggers;


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

public class USdistance {

int totalRotation = 360;
int scanDensity = 5;
UltrasonicSensor ultrasonicSensor = new UltrasonicSensor(SensorPort.S3);
File distanceFile = new File("Distances.txt");
FileOutputStream fileStream = null;

public static void main(String[] args) {
    @SuppressWarnings("unused")
    USdistance usD = new USdistance();
}

public USdistance() {
    Motor.A.setAcceleration(2000);
    Motor.A.setSpeed(50);   

    try {
        fileStream = new FileOutputStream(distanceFile);
    } catch (Exception e) {
        LCD.drawString("Can't make a file", 0, 0);
        Button.ESCAPE.waitForPress();
        System.exit(1);
    }

    DataOutputStream dataStream = new DataOutputStream(fileStream);

    Motor.A.rotate(90);
    Motor.A.resetTachoCount();
    Motor.A.backward();

    do {
        if (-(Motor.A.getTachoCount()) % scanDensity == 0 ) {
            int distance = ultrasonicSensor.getDistance();
            try {
                dataStream.writeInt(distance);
                fileStream.flush();
            } catch (IOException e) {
                LCD.drawString("Can't write to the file", 0, 1);
                Button.ESCAPE.waitForPress();
                System.exit(1);
            }
        }
    } while (-(Motor.A.getTachoCount()) < totalRotation);

    Motor.A.stop();

    try {
        fileStream.close();
    } catch (IOException e) {
        LCD.drawString("Can't save the file", 0, 1);
        Button.ESCAPE.waitForPress();
        System.exit(1);
    }

    Motor.A.rotate(270);
}
}

Thanks in advance Rob

Answer 1

I solved my problem by using:

int distance = ultrasonicSensor.getDistance();
BufferedOutputStream buffStream = new BufferedOutputStream(new FileOutputStream(new File(distances.txt)));
buffStream.write(distance.getBytes());

By using this my text file looks like this: 41 41 0 0 0 0 0 0 40 40 40 40 40 39 39 39 39 39 39 40 40 40 40 instead of 㔵㈀㔵㈀㔵㈀㔵㈀㔵㐀5㐴㐀3㌴㐀4㐴㌀6㌳㌀3㈵㔀2㈵㔀2㈵㔀2㈵㔀2㌵㔀3㌵㈀㔵㈀㔵㈀㔵㈀

Anyway thanks for your replies @SimpleCoder