Android Open Source - bluegnss4osm Sirf Utils

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License

The source code is released under:

GNU General Public License

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Java Source Code

/*
 * Copyright (C) 2010, 2011, 2012 Herbert von Broeuschmeul
 * Copyright (C) 2010, 2011, 2012 BluetoothGPS4Droid Project
 * //from  w w  w  . j ava 2 s .  c o m
 * This file is part of BluetoothGPS4Droid.
 *
 * BluetoothGPS4Droid is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * BluetoothGPS4Droid is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with BluetoothGPS4Droid. If not, see <http://www.gnu.org/licenses/>.
 */

package org.da_cha.android.bluegnss.util.sirf;

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.Formatter;
import java.util.Locale;

/**
 * Utilities for generation of SIRF III binary command.
 * 
 * It can be used to generate a array of byte corresponding 
 * to a SIRF III binary command expressed in an hexadecimal string.  
 * 
 * The input can be a complete SIRF III command or just the payload.
 * In this last case the utility will add the start and end parts of the command 
 * (including the size and the checksum).
 * 
 * @author Herbert von Broeuschmeul
 *
 */
public class SirfUtils {
  
  private static final String start ="A0A2";
  private static final String end ="B0B3";

  public static byte[] genSirfCommand(String commandHexa){
    int length = commandHexa.length()/2;    
    ByteBuffer command = ByteBuffer.allocate(length);
    command.put(new BigInteger(commandHexa,16).toByteArray(), 1,length);
    return command.array();
  }
  
  public static byte[] genSirfCommandFromPayload(String payload){
    String commandHexa = createSirfCommandFromPayload(payload);
    return genSirfCommand(commandHexa);
  }
  
  public static String createSirfCommandFromPayload(String payload){
    int length = payload.length()/2;
    String res;
    
    byte[] command = new BigInteger(payload,16).toByteArray();
    
    int checkSum = 0;
    for (byte b : command){
      checkSum += (b & 0xff);
    }
    checkSum &= 0x7FFF;
    
    res = String.format((Locale)null, "%s%04X%s%04X%s", start, length, payload, checkSum, end);
    return res;
  }
  
  public static String showSirfCommandFromPayload(String payload){
    byte[] command = genSirfCommandFromPayload(payload);
    StringBuilder out = new StringBuilder(payload.length()+16);
    Formatter fmt = new Formatter(out, null);
    for (byte b : command){
      fmt.format("%02X", b);
    }
    return out.toString();
  }
}

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