P25 LSM decoder work in progress. Adds a CQPSK decoder based on Max's (KA1RBI) scope.py and gardner loop.

The CQPSK decoder is starting to take shape, but needs more tweaking and testing.  It's not keeping a good lock on strong P25 signals.  I have to add some more features to the intrumentation package to allow me to visualize the internals of the CQPSK decoder so that I can get a better sense of what needs fine tuning.

The CQPSK decoder may work for anyone that wants to sync the repo and run the build script.

src/instrument/tap/stream/QPSKTapPanel.java

@@ -0,0 +1,145 @@
+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014 Dennis Sheirer
+ * 
+ *     This program 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.
+ * 
+ *     This program 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 this program.  If not, see <http://www.gnu.org/licenses/>
+ ******************************************************************************/
+package instrument.tap.stream;
+
+import gui.SDRTrunk;
+import instrument.gui.SampleModel;
+import instrument.tap.Tap;
+import instrument.tap.TapViewPanel;
+
+import java.awt.Color;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.geom.Ellipse2D;
+import java.util.List;
+import java.util.Observable;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import sample.complex.ComplexSample;
+
+public class QPSKTapPanel extends TapViewPanel
+{
+    private static final long serialVersionUID = 1L;
+	private final static Logger mLog = LoggerFactory.getLogger( SDRTrunk.class );
+
+	private Tap mTap;
+	private List<ComplexSample> mSamples;
+	private int mSampleCount;
+
+	public QPSKTapPanel( ComplexTap tap )
+	{
+		super( new SampleModel<ComplexTap>(), tap.getName() );
+		
+		mTap = tap;
+		mTap.addListener( getModel() );
+
+		mSampleCount = (int)( 500 * tap.getSampleRateRatio() );
+
+		getModel().setSampleCount( mSampleCount );
+		getModel().setDelay( tap.getDelay() );
+		
+		mLog.info( "Complex Tap Panel [" + tap.getName() + "] count: " + 
+			getModel().getSampleCount() + " delay:" + getModel().getDelay() );
+	}
+	
+	@Override
+    public void update( Observable arg0, Object arg1 )
+    {
+		mSamples = (List<ComplexSample>)getModel().getSamples();
+		repaint();
+    }
+	
+	public void paintComponent( Graphics g )
+	{
+		super.paintComponent( g );
+		
+		Graphics2D g2 = (Graphics2D)g;
+
+		int min = ( getHeight() < getWidth() ? getHeight() : getWidth() );
+		
+		float middle = (float)min / 2.0f;
+
+		g2.setColor( Color.DARK_GRAY );
+		
+		g2.drawLine( getWidth() / 2, 5, getWidth() / 2, getHeight() - 5 );
+		g2.drawLine( getWidth() / 2 - (int)( middle ), getHeight() / 2, 
+					 getWidth() / 2 + (int)( middle ), getHeight() / 2 );
+
+
+		if( mSamples != null && 
+			mSamples.size() > 0  )
+		{
+			g2.drawString( mLabel, 5 , 15 );
+
+			/* Set color to light gray for oldest 90% of constellations */
+			g2.setColor( Color.LIGHT_GRAY );
+
+			int counter = 0;
+
+			int threshold = (int)( mSamples.size() * 0.9f );
+
+			for( ComplexSample sample: mSamples )
+			{
+				/* Set color to foreground for newest 10% of constellations */
+				if( counter == threshold )
+				{
+					g2.setColor( getForeground() );
+				}
+				
+				float scale;
+				
+				if( sample.real() != 0 && sample.imaginary() != 0 )
+				{
+					scale = 1.0f / sample.magnitude();
+				}
+				else if( sample.real() == 0 )
+				{
+					scale = 1.0f / sample.imaginary();
+				}
+				else
+				{
+					scale = 1.0f / sample.real();
+				}
+				
+				float x = ( getWidth() / 2 ) + 
+						  ( scale *  sample.real() * middle * 0.75f * mVerticalZoom );
+				
+				if( Float.isNaN( x ) )
+				{
+					x = getWidth() / 2;
+				}
+				
+				float y = ( getHeight() / 2 ) + 
+						  ( scale * sample.imaginary() * middle * 0.75f * mVerticalZoom );
+				
+				if( Float.isNaN( y ) )
+				{
+					y = getHeight() / 2;
+				}
+				
+				g2.draw( new Ellipse2D.Float( x, y, 4.0f, 4.0f ) );
+				
+				counter++;
+			}
+		}
+		
+		g2.dispose();
+	}
+}