rtl_tcp: implement frequency correction control

lib/rtl_tcp/rtl_tcp_source_c.cc

@@ -51,6 +51,7 @@ rtl_tcp_source_c::rtl_tcp_source_c(const std::string &args) :
   _freq = 0;
   _rate = 0;
   _gain = 0;
+  _corr = 0;
   _auto_gain = false;
 
   dict_t dict = params_to_dict(args);
@@ -162,12 +163,16 @@ double rtl_tcp_source_c::get_center_freq( size_t chan )
 
 double rtl_tcp_source_c::set_freq_corr( double ppm, size_t chan )
 {
+  _src->set_freq_corr( int(ppm) );
+
+  _corr = ppm;
+
   return get_freq_corr( chan );
 }
 
 double rtl_tcp_source_c::get_freq_corr( size_t chan )
 {
-  return 0;
+  return _corr;
 }
 
 std::vector<std::string> rtl_tcp_source_c::get_gain_names( size_t chan )

lib/rtl_tcp/rtl_tcp_source_c.h

@@ -75,7 +75,7 @@ public:
   std::string get_antenna( size_t chan = 0 );
 
 private:
-  double _freq, _rate, _gain;
+  double _freq, _rate, _gain, _corr;
   bool _auto_gain;
   rtl_tcp_source_f_sptr _src;
 };

lib/rtl_tcp/rtl_tcp_source_f.cc

@@ -267,3 +267,9 @@ void rtl_tcp_source_f::set_gain(int gain)
   struct command cmd = { 0x04, gain };
   send(d_socket, (const char*)&cmd, sizeof(cmd), 0);
 }
+
+void rtl_tcp_source_f::set_freq_corr(int ppm)
+{
+  struct command cmd = { 0x05, ppm };
+  send(d_socket, (const char*)&cmd, sizeof(cmd), 0);
+}

lib/rtl_tcp/rtl_tcp_source_f.h

@@ -94,6 +94,7 @@ private:
   void set_sample_rate(int sample_rate);
   void set_gain_mode(int manual);
   void set_gain(int gain);
+  void set_freq_corr(int ppm);
 };