Activating TX Low Pass Filter in Second IF IC (#1470)

* Activating TX Low Pass Filter in Second IF IC
* solving PR conversation revisions
* Final TX LPF decision for ADSB_TX
* Small comments correction.
* Added set TX LPF also  in APRS, BurgerPgr,Jammer

firmware/application/apps/gps_sim_app.cpp

@@ -173,6 +173,8 @@ GpsSimAppView::GpsSimAppView(
         &waterfall,
     });
 
+    transmitter_model.set_baseband_bandwidth(15'000'000);  // GPS L1 signal use to have wide band spectrum, still with lobule energy -30dB's at + - 15 Mhz
+
     if (!settings_.radio_loaded()) {
         field_frequency.set_value(initial_target_frequency);
         transmitter_model.set_sampling_rate(2600000);

firmware/application/apps/soundboard_app.cpp

@@ -120,6 +120,7 @@ void SoundBoardView::start_tx(const uint32_t id) {
     );
     baseband::set_sample_rate(sample_rate);
 
+    transmitter_model.set_baseband_bandwidth(1'750'000);  // the Minimum TX LPF  1M75 is fine.
     transmitter_model.enable();
 
     tx_view.set_transmitting(true);

firmware/application/apps/ui_adsb_tx.cpp

@@ -296,6 +296,10 @@ void ADSBTxView::generate_frames() {
 void ADSBTxView::start_tx() {
     generate_frames();
 
+    /* Already tested , with SDR Angel + another Hackrf RX  and dump1090 + SDR RLT. Final conclusion is TX LPF 6 Mhz is
+     * the best settings to fulfill ADSB transponder spectrum mask requirements (<=-20 dB's at +-7Mhz , <=-40 dB's at +-23Mhz )
+     * and not showing any ADSB data decoding degradation.*/
+    transmitter_model.set_baseband_bandwidth(6'000'000);  // best settings for ADSB TX.
     transmitter_model.enable();
 
     baseband::set_adsb();

firmware/application/apps/ui_aprs_tx.cpp

@@ -57,6 +57,7 @@ void APRSTXView::start_tx() {
     // uint8_t * bb_data_ptr = shared_memory.bb_data.data;
     // text_payload.set(to_string_hex_array(bb_data_ptr + 56, 15));
 
+    transmitter_model.set_baseband_bandwidth(1'750'000);  // APRS Automatic Packet Reporting System (APRS).AFSK with NBFM , max BW= 12k5 , then TX LPF min 1M75
     transmitter_model.enable();
 
     baseband::set_afsk_data(

firmware/application/apps/ui_coasterp.cpp

@@ -67,6 +67,7 @@ void CoasterPagerView::generate_frame() {
 void CoasterPagerView::start_tx() {
     generate_frame();
 
+    transmitter_model.set_baseband_bandwidth(1'750'000);  // AFSK narrowband ,low baud,  max FM dev 150khz , std 10khz. TX LPF=1M75 the min.
     transmitter_model.enable();
 
     baseband::set_fsk_data(19 * 8, 2280000 / 1000, 5000, 32);

firmware/application/apps/ui_jammer.cpp

@@ -261,6 +261,7 @@ void JammerView::start_tx() {
 
         transmitter_model.set_rf_amp(field_amp.value());
         transmitter_model.set_tx_gain(field_gain.value());
+        transmitter_model.set_baseband_bandwidth(28'000'000);  // Although tx is narrowband , let's use Max TX LPF .
         transmitter_model.enable();
 
         baseband::set_jammer(true, (JammerType)options_type.selected_index(), options_speed.selected_index_value());
@@ -288,7 +289,8 @@ void JammerView::on_timer() {
         mscounter = 0;
         if (jamming) {
             if (cooling) {
-                if (++seconds >= field_timepause.value()) {  // Re-start TX
+                if (++seconds >= field_timepause.value()) {                // Re-start TX
+                    transmitter_model.set_baseband_bandwidth(28'000'000);  // Although tx is narrowband , let's use Max TX LPF .
                     transmitter_model.enable();
                     button_transmit.set_text("STOP");
                     baseband::set_jammer(true, (JammerType)options_type.selected_index(), options_speed.selected_index_value());

firmware/application/apps/ui_mictx.cpp

@@ -87,6 +87,10 @@ void MicTXView::set_tx(bool enable) {
         transmitting = true;
         configure_baseband();
         transmitter_model.set_target_frequency(tx_frequency);  // Now, no need: transmitter_model.set_tx_gain(tx_gain), nor (rf_amp);
+
+        /* The max. Power Spectrum Densitiy in WFM with High tone mod level (80%) and high 32kHZ subtone as fmod.  with max fdeviation 150k ,
+         BW aprox = 2 *(150K + 32K) = 364khz, then we just select the minimum TX  LPF 1M75. */
+        transmitter_model.set_baseband_bandwidth(1'750'000);
         transmitter_model.enable();
         portapack::pin_i2s0_rx_sda.mode(3);  // This is already done in audio::init but gets changed by the CPLD overlay reprogramming
     } else {

firmware/application/apps/ui_playlist.cpp

@@ -273,7 +273,7 @@ void PlaylistView::send_current_track() {
     // ReplayThread starts immediately on construction; must be set before creating.
     transmitter_model.set_target_frequency(current()->metadata.center_frequency);
     transmitter_model.set_sampling_rate(get_actual_sample_rate(current()->metadata.sample_rate));
-    transmitter_model.set_baseband_bandwidth(baseband_bandwidth);
+    transmitter_model.set_baseband_bandwidth(current()->metadata.sample_rate <= 500'000 ? 1'750'000 : 2'500'000);  // TX LPF min 1M75 for SR <=500K, and  2M5 (by experimental test) for SR >500K
     transmitter_model.enable();
 
     // Reset the transmit progress bar.

firmware/application/apps/ui_playlist.hpp

@@ -60,7 +60,6 @@ class PlaylistView : public View {
 
     // More header == less spectrum view.
     static constexpr ui::Dim header_height = 6 * 16;
-    static constexpr uint32_t baseband_bandwidth = 2'500'000;
 
     struct playlist_entry {
         std::filesystem::path path{};

firmware/application/apps/ui_rds.cpp

@@ -187,6 +187,7 @@ void RDSView::start_tx() {
     else
         frame_datetime.clear();
 
+    transmitter_model.set_baseband_bandwidth(1'750'000);  // Big Spectrum harmonics reduction, and now quicker decoding time.
     transmitter_model.enable();
 
     tx_thread = std::make_unique<RDSThread>(frames);

firmware/application/hw/max2837.cpp

@@ -122,7 +122,7 @@ void MAX2837::init() {
 
     _map.r.lpf_1.LPF_EN = 1;      /* Enable low-pass filter */
     _map.r.lpf_1.ModeCtrl = 0b01; /* Rx LPF */
-    _map.r.lpf_1.FT = 0b0000;     /* 5MHz LPF */
+    _map.r.lpf_1.FT = 0b0000;     /* 1,75MHz LPF */
 
     _map.r.spi_en.EN_SPI = 1; /* enable chip functions when ENABLE pin set */
 
@@ -233,10 +233,28 @@ void MAX2837::set_vga_gain(const int_fast8_t db) {
     flush();
 }
 
-void MAX2837::set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum) {
+void MAX2837::set_lpf_rf_bandwidth_rx(const uint32_t bandwidth_minimum) {
+    _map.r.lpf_1.ModeCtrl = 0b01; /* Address reg 2, D3-D2, Set mode lowpass filter block to Rx LPF . Active when Address 6 D<9> = 1 */
     _map.r.lpf_1.FT = filter::bandwidth_ordinal(bandwidth_minimum);
-    _dirty[Register::LPF_1] = 1;
+    flush_one(Register::LPF_1);
-    flush();
+
+    _map.r.vga_3_rx_top.LPF_MODE_SEL = 1; /* Address 6 reg, D9 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 2 D3:D2*/
+    flush_one(Register::VGA_3_RX_TOP);
+
+    _map.r.vga_3_rx_top.LPF_MODE_SEL = 0; /* Leave LPF_MODE_SEL 0 = Normal operation */
+    flush_one(Register::VGA_3_RX_TOP);
+}
+
+void MAX2837::set_lpf_rf_bandwidth_tx(const uint32_t bandwidth_minimum) {
+    _map.r.lpf_1.ModeCtrl = 0b10; /* Address 2 reg, D3-D2, Set mode lowpass filter block to Tx LPF . Active when Address 6 D<9> = 1 */
+    _map.r.lpf_1.FT = filter::bandwidth_ordinal(bandwidth_minimum);
+    flush_one(Register::LPF_1);
+
+    _map.r.vga_3_rx_top.LPF_MODE_SEL = 1; /* Address 6 reg, D9 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 2 D3:D2*/
+    flush_one(Register::VGA_3_RX_TOP);
+
+    _map.r.vga_3_rx_top.LPF_MODE_SEL = 0; /* Leave LPF_MODE_SEL 0 = Normal operation */
+    flush_one(Register::VGA_3_RX_TOP);
 }
 
 bool MAX2837::set_frequency(const rf::Frequency lo_frequency) {

firmware/application/hw/max2837.hpp

@@ -783,7 +783,8 @@ class MAX2837 : public MAX283x {
     void set_tx_vga_gain(const int_fast8_t db) override;
     void set_lna_gain(const int_fast8_t db) override;
     void set_vga_gain(const int_fast8_t db) override;
-    void set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum) override;
+    void set_lpf_rf_bandwidth_rx(const uint32_t bandwidth_minimum) override;
+    void set_lpf_rf_bandwidth_tx(const uint32_t bandwidth_minimum) override;
 #if 0
 	void rx_cal() {
 		_map.r.spi_en.EN_SPI = 1;

firmware/application/hw/max2839.cpp

@@ -278,10 +278,32 @@ void MAX2839::set_vga_gain(const int_fast8_t db) {
     configure_rx_gain();
 }
 
-void MAX2839::set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum) {
+void MAX2839::set_lpf_rf_bandwidth_rx(const uint32_t bandwidth_minimum) {
+    _map.r.lpf_vga_1.ModeCtrl = 0b01; /* Address reg 5, D9-D8, Set mode lowpass filter block to Rx LPF . Active when Address 8 D<2> = 1 */
+    flush_one(Register::LPF_VGA_1);
+
+    _map.r.rx_top_1.LPF_MODE_SEL = 1; /* Address 8 reg, D2 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 5 D<9:8> */
+    flush_one(Register::RX_TOP_1);
+
     _map.r.lpf.FT = filter::bandwidth_ordinal(bandwidth_minimum);
-    _dirty[Register::LPF] = 1;
+    flush_one(Register::LPF);
-    flush();
+
+    _map.r.rx_top_1.LPF_MODE_SEL = 0; /* Address 8 reg, D2 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 5 D<9:8> */
+    flush_one(Register::RX_TOP_1);    /* Leave LPF_MODE_SEL 0 = Normal operation */
+}
+
+void MAX2839::set_lpf_rf_bandwidth_tx(const uint32_t bandwidth_minimum) {
+    _map.r.lpf_vga_1.ModeCtrl = 0b10; /* Address reg 5, D9-D8, Set mode lowpass filter block to Tx LPF . Active when Address 8 D<2> = 1 */
+    flush_one(Register::LPF_VGA_1);
+
+    _map.r.rx_top_1.LPF_MODE_SEL = 1; /* Address 8 reg, D2 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 5 D<9:8> */
+    flush_one(Register::RX_TOP_1);
+
+    _map.r.lpf.FT = filter::bandwidth_ordinal(bandwidth_minimum);
+    flush_one(Register::LPF);
+
+    _map.r.rx_top_1.LPF_MODE_SEL = 0; /* Address 8 reg, D2 bit:LPF mode mux, LPF_MODE_SEL 0 = Normal operation, 1 = Operating mode is programmed Address 5 D<9:8> */
+    flush_one(Register::RX_TOP_1);    /* Leave LPF_MODE_SEL 0 = Normal operation */
 }
 
 bool MAX2839::set_frequency(const rf::Frequency lo_frequency) {

firmware/application/hw/max2839.hpp

@@ -686,7 +686,8 @@ class MAX2839 : public MAX283x {
     void set_tx_vga_gain(const int_fast8_t db) override;
     void set_lna_gain(const int_fast8_t db) override;
     void set_vga_gain(const int_fast8_t db) override;
-    void set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum) override;
+    void set_lpf_rf_bandwidth_rx(const uint32_t bandwidth_minimum) override;
+    void set_lpf_rf_bandwidth_tx(const uint32_t bandwidth_minimum) override;
     bool set_frequency(const rf::Frequency lo_frequency) override;
     void set_rx_lo_iq_calibration(const size_t v) override;
     void set_rx_buff_vcm(const size_t v) override;

firmware/application/hw/max283x.hpp

@@ -123,7 +123,8 @@ class MAX283x {
     virtual void set_tx_vga_gain(const int_fast8_t db);
     virtual void set_lna_gain(const int_fast8_t db);
     virtual void set_vga_gain(const int_fast8_t db);
-    virtual void set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum);
+    virtual void set_lpf_rf_bandwidth_rx(const uint32_t bandwidth_minimum);
+    virtual void set_lpf_rf_bandwidth_tx(const uint32_t bandwidth_minimum);
 
     virtual bool set_frequency(const rf::Frequency lo_frequency);
 

firmware/application/radio.cpp

@@ -232,8 +232,12 @@ void set_tx_gain(const int_fast8_t db) {
     second_if->set_tx_vga_gain(db);
 }
 
-void set_baseband_filter_bandwidth(const uint32_t bandwidth_minimum) {
+void set_baseband_filter_bandwidth_rx(const uint32_t bandwidth_minimum) {
-    second_if->set_lpf_rf_bandwidth(bandwidth_minimum);
+    second_if->set_lpf_rf_bandwidth_rx(bandwidth_minimum);
+}
+
+void set_baseband_filter_bandwidth_tx(const uint32_t bandwidth_minimum) {
+    second_if->set_lpf_rf_bandwidth_tx(bandwidth_minimum);
 }
 
 void set_baseband_rate(const uint32_t rate) {

firmware/application/radio.hpp

@@ -50,7 +50,8 @@ void set_rf_amp(const bool rf_amp);
 void set_lna_gain(const int_fast8_t db);
 void set_vga_gain(const int_fast8_t db);
 void set_tx_gain(const int_fast8_t db);
-void set_baseband_filter_bandwidth(const uint32_t bandwidth_minimum);
+void set_baseband_filter_bandwidth_rx(const uint32_t bandwidth_minimum);
+void set_baseband_filter_bandwidth_tx(const uint32_t bandwidth_minimum);
 void set_baseband_rate(const uint32_t rate);
 void set_antenna_bias(const bool on);
 

firmware/application/receiver_model.cpp

@@ -270,7 +270,7 @@ void ReceiverModel::update_tuning_frequency() {
 }
 
 void ReceiverModel::update_baseband_bandwidth() {
-    radio::set_baseband_filter_bandwidth(baseband_bandwidth());
+    radio::set_baseband_filter_bandwidth_rx(baseband_bandwidth());
 }
 
 void ReceiverModel::update_sampling_rate() {

firmware/application/transmitter_model.cpp

@@ -139,7 +139,7 @@ void TransmitterModel::update_tuning_frequency() {
 }
 
 void TransmitterModel::update_baseband_bandwidth() {
-    radio::set_baseband_filter_bandwidth(baseband_bandwidth());
+    radio::set_baseband_filter_bandwidth_tx(baseband_bandwidth());
 }
 
 void TransmitterModel::update_sampling_rate() {