Page 75 - The Definitive Guide to Building Java Robots

Preston_5564C03.fm Page 56 Wednesday, October 5, 2005 7:21 AM

56 CHAPTER 3 ■ MOTION

try {
// create serial port
StandardSerialPort serialPort = new StandardSerialPort(1);
// increment position by 5 each time in loop
for (int pos = 0; pos < 255; pos = pos + 5) {
// create byte array for ssc commands
byte[] sscCmd = new byte[] { (byte) 255, 0, (byte) pos };
// send byte array to serial port
serialPort.write(sscCmd);
// pause between commands
Thread.sleep(100);
}
// close serail port
serialPort.close();
} catch (Exception e) {
// print stack trace and exit.
e.printStackTrace();
System.exit(1);
}
}
}
While the preceding class does just what I want it to, I thought that given all the work in the
coming sections and chapters it would be a good idea to standardize communication to the SSC
because its communication protocol is fixed. To do this, I created the interface SSCProtocol.java. It
has a single method defined, move(pin, pos). The method has the following parameters: pin—
the pin position of where the servo is plugged in; and pos—the position of the servo from 0 to 255.
I also added a few constants to simplify classes using this protocol. (See Example 3-3.)

Example 3-3. SSCProtocol.java
package com.scottpreston.javarobot.chapter3;

public interface SSCProtocol {

// maximum
public static final byte MAX = (byte) 255;
// neutral
public static final byte NEUTRAL = (byte)127;
// minimum
public static final byte MIN = (byte) 0;

/**
* @param pin - connector on the MiniSSC 0-7
* @param pos - byte from 0-255
*/
public void move(int pin, int pos) throws Exception;
}