Mindstorms

MindStorms is a ``Robotics Invention System''

• A 16-bit computer called the RCX (a 16MHz Hitachi H8/3297), with 32k RAM
• The RCX can control 3 motors and read from 3 sensors
• Additional Lego parts - gears, wheels, sensors, motors
• Software can be downloaded by an infra-red link on a serial port
• Programs can be downloaded and run, or "immediate" commands can be run
• Normally programmed from a visual programming environment or from VB
• On a PC, interface to RCX is managed by an OCX
• Low-level machine-code is sent across the IR link

Lego and Java

• The Mindstorms robot only has 32k of RAM
• The CLDC configuration (using the KVM) requires 160k
• Therefore, Mindstorms cannot run as a J2ME device
• There is a really tiny version of Java that will run in the Mindstorms

Tiny devices and proxies

Run a proxy on a Java-capable device that "represents" the device

Mindstorms control

• The Mindstorms robot has a microcontroller that defines an instruction set as bytecodes, including

  Mindstorms programs

  • Programs can be downloaded to the Mindstorms using the IR link
  • Single instructions can also be downloaded and run immediately, again by the IR link

  Mindstorms proxy

  A proxy for the Mindstorms robot is built using the following components

  • Native code serial port DLL
  • Java CommAPI
  • Proxy on top of this
  

  RCXPort

  Dario Laverde has defined a proxy class

  
  package rcx;
  
  public class RCXPort {
      public RCXPort(String port);
      public void addRCXListener(RCXListener rl);
      public boolean open();
      public void close();
      public boolean isOpen();
      public OutputStream getOutputStream();
      public InputStream getInputStream();
      public synchronized boolean write(byte[] bArray);
      public String getLastError();
  }
  

  Example use of RCXPort

  
  import rcx.*;
  
  public class TestRCX implements RCXListener {
      static final String PORT_NAME = "/dev/ttyS0"; // Linux
  
      public TestRCX() {
  	RCXPort port = new RCXPort(PORT_NAME);
  
  	port.addRCXListener(this);
  
  	byte[] byteArray;
  
  	// send ping message, reply should be e7 or ef
  	byteArray = RCXOpcode.parseString("10"); // Alive
  	port.write(byteArray);
  
  	// beep twice
  	byteArray = RCXOpcode.parseString("51 01"); // Play sound
  	port.write(byteArray);
  
  	// turn motor A on (forwards)
  	byteArray = RCXOpcode.parseString("e1 81"); // Set motor direction
  	port.write(byteArray);
  	byteArray = RCXOpcode.parseString("21 81"); // Set motor on
  	port.write(byteArray);
  	try {
  	    Thread.currentThread().sleep(1000);
  	} catch(Exception e) {
  	}
  
  	// turn motor A off
  	byteArray = RCXOpcode.parseString("21 41"); // Set motor off
  	port.write(byteArray);
  
  	// turn motor A on (backwards)
  	byteArray = RCXOpcode.parseString("e1 41"); // Set motor direction
  	port.write(byteArray);
  	byteArray = RCXOpcode.parseString("21 81"); // Set motor on
  	port.write(byteArray);
  	try {
  	    Thread.currentThread().sleep(1000);
  	} catch(Exception e) {
  	}
  
  	// turn motor A off
  	byteArray = RCXOpcode.parseString("21 41"); // Set motor off
  	port.write(byteArray);
      }
  
      /**
       * listener method for messages from the RCX
       */
      public void receivedMessage(byte[] message) {
  	if (message == null) {
  	    return;
  	}
  	StringBuffer sbuffer = new StringBuffer();
          for(int n = 0; n < message.length; n++) {       
              int newbyte = (int) message[n];
              if (newbyte < 0) {
  		newbyte += 256;
  	    }
              sbuffer.append(Integer.toHexString(newbyte) + " ");
  	}
  	System.out.println("response: " + sbuffer.toString());
      }
  
      /**
       * listener method for error messages from the RCX
       */
      public void receivedError(String error) {
  	System.err.println("Error: " + error);
      }
      
      public static void main(String[] args) {
  	new TestRCX();
      }
      
  } // TestRCX
  

  ---

  Jan Newmarch (http://jan.newmarch.name)
  jan@newmarch.name
  Last modified: Mon Mar 31 04:29:33 EST 2003
  Copyright ©Jan Newmarch
  Copyright © Jan Newmarch, Monash University, 2007
  This work is licensed under a Creative Commons License
  The moral right of Jan Newmarch to be identified as the author of this page has been asserted.

  Instruction	Bytecode
  PING	0x10
  SETMOTORPOWER	0x13
  CALLSUB	0x17
  PLAYSOUND	0x51
  SETMOTOR	0x21