[PATCH] rfspace: Add PPM correction

[argilo]

From: Clayton Smith <arg...@gmail.com>

This patch was originally written by Alexandru Csete and posted at
https://github.com/csete/gr-osmosdr-gqrx/commit/d66df300. The only
change I made was to rename the _freq_corr_ppm variable to
_freq_corr, since many other devices use that name.

This patch used to be included in Gqrx releases, so it should work
correctly.
---
 lib/rfspace/rfspace_source_c.cc | 17 +++++++++++++----
 lib/rfspace/rfspace_source_c.h  |  2 ++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/lib/rfspace/rfspace_source_c.cc b/lib/rfspace/rfspace_source_c.cc
index 314dfc732d..113588a5d4 100644
--- a/lib/rfspace/rfspace_source_c.cc
+++ b/lib/rfspace/rfspace_source_c.cc
@@ -103,6 +103,7 @@ rfspace_source_c::rfspace_source_c (const std::string &args)
     _nchan(1),
     _sample_rate(NAN),
     _bandwidth(0.0f),
+    _freq_corr(0.0),
     _fifo(NULL)
 {
   std::string host = "";
@@ -446,6 +447,8 @@ rfspace_source_c::rfspace_source_c (const std::string &args)
     _thread = gr::thread::thread( 
boost::bind(&rfspace_source_c::tcp_keepalive_task, this) );
   }
 
+  _center_freq = get_center_freq();
+
 #if 0
   std::cerr << "sample_rates: " << get_sample_rates().to_pp_string() << 
std::endl;
   std::cerr << "sample rate: " << (uint32_t)get_sample_rate() << std::endl;
@@ -600,7 +603,7 @@ static size_t read_bytes( int fd, char *data, size_t size, 
bool &run )
     int nread = read( fd, &data[nbytes], 1 );
 
     if ( nread == 0 )
-      continue;   
+      continue;
 
     if ( nread < 0 )
       break;
@@ -1378,7 +1381,10 @@ osmosdr::freq_range_t rfspace_source_c::get_freq_range( 
size_t chan )
 
 double rfspace_source_c::set_center_freq( double freq, size_t chan )
 {
-  uint32_t u32_freq = freq;
+  uint32_t u32_freq;
+
+  u32_freq = freq * (1.0 + _freq_corr * 0.000001);
+  _center_freq = freq;
 
   /* SDR-IQ 5.2.2 Receiver Frequency */
   /* SDR-IP 4.2.2 Receiver Frequency */
@@ -1395,7 +1401,7 @@ double rfspace_source_c::set_center_freq( double freq, 
size_t chan )
 
   transaction( tune, sizeof(tune) );
 
-  return get_center_freq( chan );
+  return _center_freq;
 }
 
 double rfspace_source_c::get_center_freq( size_t chan )
@@ -1423,12 +1429,15 @@ double rfspace_source_c::get_center_freq( size_t chan )
 
 double rfspace_source_c::set_freq_corr( double ppm, size_t chan )
 {
+  _freq_corr = ppm;
+  set_center_freq( _center_freq, chan );
+
   return get_freq_corr( chan );
 }
 
 double rfspace_source_c::get_freq_corr( size_t chan )
 {
-  return 0;
+  return _freq_corr;
 }
 
 std::vector<std::string> rfspace_source_c::get_gain_names( size_t chan )
diff --git a/lib/rfspace/rfspace_source_c.h b/lib/rfspace/rfspace_source_c.h
index 996f47b392..42bb6de6ac 100644
--- a/lib/rfspace/rfspace_source_c.h
+++ b/lib/rfspace/rfspace_source_c.h
@@ -145,6 +145,8 @@ private: /* members */
   size_t _nchan;
   double _sample_rate;
   double _bandwidth;
+  double _center_freq;
+  double _freq_corr;
 
   gr::thread::thread _thread;
   bool _run_usb_read_task;
-- 
2.25.1