Gps default frequency (portapack-mayhem#1309)

* Default frequency

* Default frequency

* Use sample rate from .ini file if present

* Eliminate unneeded sampling_rate variable

* Eliminate unneeded sampling_rate variable

firmware/application/apps/gps_sim_app.cpp

@@ -63,17 +63,15 @@ void GpsSimAppView::on_file_changed(const fs::path& new_file_path) {
 
     if (metadata) {
         field_frequency.set_value(metadata->center_frequency);
-        sample_rate = metadata->sample_rate;
-    } else {
-        sample_rate = 2600000;
+        transmitter_model.set_sampling_rate(metadata->sample_rate);
     }
 
     // UI Fixup.
-    text_sample_rate.set(unit_auto_scale(sample_rate, 3, 1) + "Hz");
+    text_sample_rate.set(unit_auto_scale(transmitter_model.sampling_rate(), 3, 1) + "Hz");
     progressbar.set_max(file_size);
     text_filename.set(truncate(file_path.filename().string(), 12));
 
-    auto duration = ms_duration(file_size, sample_rate, 2);
+    auto duration = ms_duration(file_size, transmitter_model.sampling_rate(), 2);
     text_duration.set(to_string_time_ms(duration));
 
     button_play.focus();
@@ -129,7 +127,6 @@ void GpsSimAppView::start() {
             });
     }
 
-    transmitter_model.set_sampling_rate(sample_rate);
     transmitter_model.enable();
 }
 
@@ -176,6 +173,11 @@ GpsSimAppView::GpsSimAppView(
         &waterfall,
     });
 
+    if (!settings_.loaded()) {
+        field_frequency.set_value(initial_target_frequency);
+        transmitter_model.set_sampling_rate(2600000);
+    }
+
     field_frequency.set_step(5000);
 
     button_play.on_select = [this](ImageButton&) {

firmware/application/apps/gps_sim_app.hpp

@@ -54,6 +54,8 @@ class GpsSimAppView : public View {
     std::string title() const override { return "GPS Sim TX"; };
 
    private:
+    static constexpr uint32_t initial_target_frequency = 1575420000;
+
     NavigationView& nav_;
     RxRadioState radio_state_{
         3000000 /* bandwidth */,
@@ -64,7 +66,6 @@ class GpsSimAppView : public View {
 
     static constexpr ui::Dim header_height = 3 * 16;
 
-    uint32_t sample_rate = 0;
     int32_t tx_gain{47};
     bool rf_amp{true};                                       // aux private var to store temporal, same as Replay App rf_amp user selection.
     static constexpr uint32_t baseband_bandwidth = 3000000;  // filter bandwidth