Added optional support for Sparkfun SiGe GN3S USB GPS RF sampler:

- Added a pre-compiled custom GN3S firmware.
- Added a fully-compliant GNU Radio source block for GN3S USB dongle. It can be used also from GNU Radio companion and from Python applications.
- Added a new GN3S_Signal_Source block. It is possible to disable the GN3S signal source compilation. See README.

git-svn-id: https://svn.code.sf.net/p/gnss-sdr/code/trunk@217 64b25241-fba3-4117-9849-534c7e92360d

drivers/gr-gn3s/include/gn3s_source.h

@@ -0,0 +1,80 @@
+/*----------------------------------------------------------------------------------------------*/
+//
+// FILENAME: gps_source.h
+//
+// DESCRIPTION: Defines the GPS_Source class.
+//
+// DEVELOPERS: Gregory W. Heckler (2003-2009)
+//
+// LICENSE TERMS: Copyright (c) Gregory W. Heckler 2009
+//
+// This file is part of the GPS Software Defined Radio (GPS-SDR)
+//
+// The GPS-SDR 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 2 of
+// the License, or (at your option) any later version. The GPS-SDR 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.
+//
+// Note:  Comments within this file follow a syntax that is compatible with
+//        DOXYGEN and are utilized for automated document extraction
+//
+// Reference:
+/*----------------------------------------------------------------------------------------------*/
+
+#ifndef GN3S_SOURCE_H_
+#define GN3S_SOURCE_H_
+
+#include "gn3s_defines.h"
+#include "gn3s.h"
+
+/*! \ingroup CLASSES
+ *
+ */
+class gn3s_Source
+{
+
+	private:
+
+		/* Generic variables */
+		int source_type;		//!< Source type
+		int sample_mode;		//!< Sample mode
+		int leftover;			//!< Leftover bytes for USRP double buffering
+		int bwrite;			//!< Bytes somthing something?
+		int ms_count;			//!< Count the numbers of ms processed
+
+		bool flag_first_read;
+		/* Tag overflows */
+		time_t rawtime;
+		struct tm * timeinfo;
+
+		/* AGC Values */
+		int agc_scale;		//!< To do the AGC
+		int overflw;			//!< Overflow counter
+		int soverflw;			//!< Overflow counter
+
+		/* Data buffers */
+		signed char gbuff[GN3S_SAMPS_5MS*2]; 	//!< Byte buffer for GN3S
+		GN3S_CPX buff[GN3S_SAMPS_5MS]; 		//!< Base buffer for GN3S
+
+		/* SOURCE_SIGE_GN3S Handles */
+		gn3s *gn3s_a;
+
+	private:
+
+		void Open_GN3S();			//!< Open the SparkFun GN3S Sampler
+		void Close_GN3S();			//!< Close the SparkFun GN3S Sampler
+		void Read_GN3S(gn3s_ms_packet *_p,int n_samples);	//!< Read from the SparkFun GN3S Sampler
+
+	public:
+
+		gn3s_Source();	//!< Create the GPS source with the proper hardware type
+		~gn3s_Source();					//!< Kill the object
+		void Read(gn3s_ms_packet *_p,int n_samples);		//!< Read in a single ms of data
+		int getScale(){return(agc_scale);}
+		int getOvrflw(){return(overflw);}
+
+};
+
+#endif /* GN3S_SOURCE_H_ */