Recipe 12.8 Program: Penman Plotter

The program in Example 12-10 is an outgrowth of the Plotter class from Recipe 9.12. It connects to a Penman plotter. These serial-port plotters were made in the United Kingdom in the 1980s, so it is unlikely that you will meet one. However, several companies still make pen plotters. See Figure 12-4 for a photograph of the plotter in action.
Figure 12-4. Penman plotter in action

Example 12-10. Penman.java

import java.io.*; import javax.comm.*; import java.util.*; /**  * A Plotter subclass for drawing on a Penman plotter.  * These were made in the UK and sold into North American markets.  * It is a little "turtle" style robot plotter that communicates  * over a serial port. For this, we use the "Java Communications" API.  *  */ public class Penman  extends Plotter {     private final String OK_PROMPT = "\r\n!";     private final int MAX_REPLY_BYTES = 50;    // paranoid upper bound     private SerialPort tty;     private DataInputStream is;     private DataOutputStream os;     /** Construct a Penman plotter object */     public Penman( ) throws NoSuchPortException,PortInUseException,             IOException,UnsupportedCommOperationException {         super( );         init_comm("COM2");        // setup serial commx         init_plotter( );        // set plotter to good state     }     private void init_plotter( ) {         send("I"); expect('!');    // eat VERSION etc., up to !         send("I"); expect('!');    // wait for it!         send("H");        // find home position         expect('!');    // wait for it!         send("A");        // Set to use absolute coordinates         expect('!');         curx = cury = 0;         penUp( );     }     //     // PUBLIC DRAWING ROUTINES     //     public void setFont(String fName, int fSize) {         // Font name is ignored for now...         // Penman's size is in mm, fsize in points (inch/72).         int size = (int)(fSize*25.4f/72);         send("S"+size + ","); expect(OK_PROMPT);         System.err.println("Font set request: " + fName + "/" + fSize);     }     public void drawString(String mesg) {         send("L" + mesg + "\r"); expect(OK_PROMPT);     }     /** Move to a relative location */     public void rmoveTo(int incrx, int incry){         moveTo(curx + incrx, cury + incry);     }     /** move to absolute location */     public void moveTo(int absx, int absy) {         System.err.println("moveTo ["+absx+","+absy+"]");         curx = absx;         cury = absy;         send("M" + curx + "," + cury + ","); expect(OK_PROMPT);     }     private void setPenState(boolean up) {         penIsUp = up;         System.err.println("Pen Up is ["+penIsUp+"]");     }     public void penUp( ) {         setPenState(true);         send("U"); expect(OK_PROMPT);     }     public void penDown( ) {         setPenState(false);         send("D"); expect(OK_PROMPT);     }     public void penColor(int c) {         penColor = (c%3)+1;        // only has 3 pens, 4->1         System.err.println("PenColor is ["+penColor+"]");         send("P" + c + ","); expect(OK_PROMPT);     }     //     // PRIVATE COMMUNICATION ROUTINES     // (XXX Should re-use CommPortOpen here).     private void init_comm(String portName) throws             IOException, UnsupportedCommOperationException {         // get list of ports available on this particular computer.         // Enumeration pList = CommPortIdentifier.getPortIdentifiers( );         // Print the list. A GUI program would put these in a chooser!         // while (pList.hasMoreElements( )) {             // CommPortIdentifier cpi = (CommPortIdentifier)pList.nextElement( );             // System.err.println("Port " + cpi.getName( ));         // }                  // Open a port.          CommPortIdentifier port =             CommPortIdentifier.getPortIdentifier(portName);         // This form of openPort takes an Application Name and a timeout.         tty = (SerialPort) port.openPort("Penman Driver", 1000);         // set up the serial port         tty.setSerialPortParams(9600, SerialPort.DATABITS_8,             SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);         tty.setFlowControlMode(SerialPort.FLOWCONTROL_RTSCTS_OUT|             SerialPort.FLOWCONTROL_RTSCTS_OUT);         // Get the input and output streams         is = new DataInputStream(tty.getInputStream( ));         os = new DataOutputStream(tty.getOutputStream( ));     }     /** Send a command to the plotter. Although the argument is a String,      * we send each char as a *byte*, so avoid 16-bit characters!      * Not that it matters: the Penman only knows about 8-bit chars.      */     private    void send(String s) {         System.err.println("sending " + s + "...");         try {             for (int i=0; i<s.length( ); i++)                 os.writeByte(s.charAt(i));         } catch(IOException e) {             e.printStackTrace( );         }     }     /** Expect a given CHAR for a result */     private    void expect(char s) {         byte b;         try {             for (int i=0; i<MAX_REPLY_BYTES; i++){                 if ((b = is.readByte( )) == s) {                         return;                 }                 System.err.print((char)b);             }         } catch (IOException e) {             System.err.println("Penman:expect(char "+s+"): Read failed");             System.exit(1);         }         System.err.println("ARGHH!");     }     /** Expect a given String for a result */     private    void expect(String s) {         byte ans[] = new byte[s.length( )];         System.err.println("expect " + s + " ...");         try {             is.read(ans);         } catch (IOException e) {             System.err.println("Penman:expect(String "+s+"): Read failed");             System.exit(1);         };         for (int i=0; i<s.length( ) && i<ans.length; i++)             if (ans[i] != s.charAt(i)) {                 System.err.println("MISMATCH");                 break;             }         System.err.println("GOT: " + new String(ans));     } }
Figure 12-4. Penman plotter in action

Example 12-10. Penman.java

See Also
