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leJOS (pronounced like the Spanish word "lejos" for "far") is a tiny Java Virtual Machine. In 2013 it was ported to the LEGO EV3 brick.
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package lejos.hardware.device;

import lejos.hardware.port.I2CPort;
import lejos.hardware.port.Port;
import lejos.hardware.sensor.I2CSensor;
import lejos.remote.rcx.Opcode;

import java.util.*;

/**
 * Supports for HiTechnic NXT IRLink Sensor (NIL1046) IRLink.
 * 
 * @author Lawrie Griffiths
 *
 */
public class IRLink extends I2CSensor implements Opcode, IRTransmitter {
	
	/*
	 * Documentation: http://www.hitechnic.com/cgi-bin/commerce.cgi?preadd=action&key=NIL1046
	 * 
	 * ProductId: "HiTechnc"
	 * SensorType: "IRLink"
	 * (confirmed for version " V1.2")
	 */
	
	//Registers
	private final static byte TX_BUFFER = 0x40; // 40 to 4C
	private final static byte TX_BUFFER_LEN = 0x4D;
	private final static byte TX_MODE = 0x4E;
	private final static byte TX_BUFFER_FLAG = 0x4F;
	
	private final static byte TX_MAX_BUFFER_LEN = 13;
	
	// IRLink transmission modes
	private final static byte TX_MODE_RCX = 0;
	private final static byte TX_MODE_TRAIN = 1;
	private final static byte TX_MODE_PF = 2;
	
	// PF Modes
	public final static byte PF_MODE_COMBO_DIRECT = 1;
	
	// IR PF signal encoding parameters
	private final byte MAX_BITS = TX_MAX_BUFFER_LEN * 8;
	private final byte STOP_START_PAUSE = 7;
	private final byte LOW_BIT_PAUSE = 2;
	private final byte HIGH_BIT_PAUSE = 4;
	
	// PF motor operations
	public static final byte PF_FLOAT = 0;
	public static final byte PF_FORWARD = 1;
	public static final byte PF_BACKWARD = 2;
	public static final byte PF_BRAKE = 3;
	
	// RCX Remote operation code
	public static int RCX_REMOTE_BEEP  = 0x8000;
	public static int RCX_REMOTE_STOP  = 0x4000;
	public static int RCX_REMOTE_P5    = 0x2000;
	public static int RCX_REMOTE_P4    = 0x1000;
	public static int RCX_REMOTE_P3    = 0x0800;
	public static int RCX_REMOTE_P2    = 0x0400;
	public static int RCX_REMOTE_P1    = 0x0200;
	public static int RCX_REMOTE_C_BWD = 0x0100;
	public static int RCX_REMOTE_B_BWD = 0x0080;
	public static int RCX_REMOTE_A_BWD = 0x0040;
	public static int RCX_REMOTE_C_FWD = 0x0020;
	public static int RCX_REMOTE_B_FWD = 0x0010;
	public static int RCX_REMOTE_A_FWD = 0x0008;
	public static int RCX_REMOTE_MSG3  = 0x0004;
	public static int RCX_REMOTE_MSG2  = 0x0002;
	public static int RCX_REMOTE_MSG1  = 0x0001;
	
	private byte toggle = 0;
	
	private BitSet bits = new BitSet(MAX_BITS);
	private int nextBit = 0;

    public IRLink(I2CPort port) {
        super(port);
    }
    
    public IRLink(Port port) {
        super(port);
    }
    
	/**
	 * Send commands to both motors.
	 * Uses PF Combo direct mode.
	 * 
	 * @param channel the channel number (0-3)
	 * @param opA Motor A operation
	 * @param opB Motor B operation
	 */
	public void sendPFComboDirect(int channel, int opA, int opB) {
		sendPFCommand(channel, PF_MODE_COMBO_DIRECT, opB << 2 | opA);
	}

	private void sendPFCommand(int channel, int mode, int data) {
		byte nibble1 = (byte) ((toggle << 3) | channel);
		byte lrc = (byte) (0xF ^ nibble1 ^ mode ^ data);
		int pfData = (nibble1 << 12) | (mode << 8) | (data << 4) | lrc;

		clearBits();
		nextBit = 0;
		setBit(STOP_START_PAUSE); // Start
		for(int i=15;i>=0;i--) {
			setBit(((pfData >> i) & 1) == 0 ? LOW_BIT_PAUSE : HIGH_BIT_PAUSE);
		}
		setBit(STOP_START_PAUSE); // Stop
		toggle ^= 1;
		byte [] pfCommand = new byte[16];
		
		for(int i =0;i> 8);
		buf[2] = (byte) (msg & 0xFF);
		sendPacket(buf);
	}
	
	public void runProgram(int programNumber) {
		sendRemoteCommand(RCX_REMOTE_P1 << (programNumber -1));
	}
	
	public void beep() {
		sendRemoteCommand(RCX_REMOTE_BEEP);
	}
	
	public void stopAllPrograms() {
		sendRemoteCommand(RCX_REMOTE_STOP);		
	}
	
	public void forwardStep(int motor) {
		sendRemoteCommand(RCX_REMOTE_A_FWD << motor);
	}
	
	public void backwardStep(int motor) {
		sendRemoteCommand(RCX_REMOTE_A_BWD << motor);
	}
}