Support squelch in pocsag (#1415)

* Support squelch in pocsag

* Revert smooth threshold

firmware/application/apps/pocsag_app.cpp

@@ -95,6 +95,7 @@ POCSAGAppView::POCSAGAppView(NavigationView& nav)
          &field_lna,
          &field_vga,
          &field_frequency,
+         &field_squelch,
          &field_volume,
          &image_status,
          &text_packet_count,
@@ -111,6 +112,11 @@ POCSAGAppView::POCSAGAppView(NavigationView& nav)
 
     logger.append(LOG_ROOT_DIR "/POCSAG.TXT");
 
+    field_squelch.set_value(receiver_model.squelch_level());
+    field_squelch.on_change = [this](int32_t v) {
+        receiver_model.set_squelch_level(v);
+    };
+
     button_ignore_last.on_select = [this](Button&) {
         settings_.enable_ignore = true;
         settings_.address_to_ignore = last_address;
@@ -122,8 +128,8 @@ POCSAGAppView::POCSAGAppView(NavigationView& nav)
     };
 
     refresh_ui();
-    receiver_model.enable();
     audio::output::start();
+    receiver_model.enable();
     baseband::set_pocsag();
 }
 

firmware/application/apps/pocsag_app.hpp

@@ -136,10 +136,7 @@ class POCSAGAppView : public View {
     bool hide_addr_only() const { return settings_.hide_addr_only; };
 
     NavigationView& nav_;
-    RxRadioState radio_state_{
-        12'500,     // POCSAG is FSK +/- 4.5MHz, 12k5 is a good filter.
-        3'072'000,  // Match baseband_fs in proc_pocsag.
-    };
+    RxRadioState radio_state_{};
 
     // Settings
     POCSAGSettings settings_{};
@@ -161,24 +158,33 @@ class POCSAGAppView : public View {
     void on_stats(const POCSAGStatsMessage* stats);
 
     uint32_t last_address = 0xFFFFFFFF;
-    pocsag::POCSAGState pocsag_state{};
+    pocsag::EccContainer ecc{};
+    pocsag::POCSAGState pocsag_state{&ecc};
     POCSAGLogger logger{};
     uint16_t packet_count = 0;
 
-    RFAmpField field_rf_amp{
-        {13 * 8, 0 * 16}};
-    LNAGainField field_lna{
-        {15 * 8, 0 * 16}};
-    VGAGainField field_vga{
-        {18 * 8, 0 * 16}};
-    RSSI rssi{
-        {21 * 8, 3, 6 * 8, 4}};
-    Audio audio{
-        {21 * 8, 8, 6 * 8, 4}};
-
     RxFrequencyField field_frequency{
         {0 * 8, 0 * 8},
         nav_};
+
+    RFAmpField field_rf_amp{
+        {11 * 8, 0 * 16}};
+    LNAGainField field_lna{
+        {13 * 8, 0 * 16}};
+    VGAGainField field_vga{
+        {16 * 8, 0 * 16}};
+
+    RSSI rssi{
+        {19 * 8 - 4, 3, 6 * 8, 4}};
+    Audio audio{
+        {19 * 8 - 4, 8, 6 * 8, 4}};
+
+    NumberField field_squelch{
+        {25 * 8, 0 * 16},
+        2,
+        {0, 99},
+        1,
+        ' '};
     AudioVolumeField field_volume{
         {28 * 8, 0 * 16}};
 

firmware/baseband/proc_pocsag.cpp

@@ -24,12 +24,13 @@
 
 #include "proc_pocsag.hpp"
 
+#include "dsp_iir_config.hpp"
 #include "event_m4.hpp"
 
-#include <cstdint>
-#include <cstddef>
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
+#include <cstddef>
 
 void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
     // This is called at 1500Hz
@@ -41,9 +42,13 @@ void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
     const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
     const auto channel_out = channel_filter.execute(decim_1_out, dst_buffer);
     auto audio = demod.execute(channel_out, audio_buffer);
-    smooth.Process(audio.p, audio.count);  // Smooth the data to make decoding more accurate
+
+    // Output audio pre-smoothing so squelch actually works.
+    // NB: It's useful to output *after* when debugging the smoothing filter.
     audio_output.write(audio);
 
+    // Smooth the data to make decoding more accurate.
+    smooth.Process(audio.p, audio.count);
     processDemodulatedSamples(audio.p, 16);
     extractFrames();
 }
@@ -71,8 +76,23 @@ int POCSAGProcessor::OnDataFrame(int len, int baud) {
 }
 
 void POCSAGProcessor::on_message(const Message* const message) {
-    if (message->id == Message::ID::POCSAGConfigure)
-        configure();
+    switch (message->id) {
+        case Message::ID::POCSAGConfigure:
+            configure();
+            break;
+
+        case Message::ID::NBFMConfigure: {
+            auto config = reinterpret_cast<const NBFMConfigureMessage*>(message);
+            audio_output.configure(
+                audio_24k_hpf_300hz_config,
+                audio_8k_deemph_300_6_config,
+                config->squelch_level / 100.0);
+            break;
+        }
+
+        default:
+            break;
+    }
 }
 
 void POCSAGProcessor::configure() {
@@ -91,13 +111,10 @@ void POCSAGProcessor::configure() {
     decim_1.configure(taps_11k0_decim_1.taps, 131072);
     channel_filter.configure(taps_11k0_channel.taps, 2);
     demod.configure(demod_input_fs, 4'500);  // FSK +/- 4k5Hz.
-    // Smoothing should be roughly sample rate over max baud
-    // 24k / 3.2k is 7.5
-    smooth.SetSize(8);
 
-    // TODO: support squelch?
-    // audio_output.configure(message.audio_hpf_config, message.audio_deemph_config, (float)message.squelch_level / 100.0);
-    audio_output.configure(false);
+    // Smoothing should be roughly sample rate over max baud
+    // 24k / 3.2k = 7.5
+    smooth.SetSize(8);
 
     // Set up the frame extraction, limits of baud
     setFrameExtractParams(demod_input_fs, 4000, 300, 32);

firmware/baseband/proc_pocsag.hpp

@@ -106,10 +106,10 @@ class SmoothVals {
 
         // Use a rolling smoothed value while processing the buffer
         for (int buffPos = 0; buffPos < numVals; ++buffPos) {
-            m_pos = (m_pos + 1);  // Increment the position in the stored values
+            m_pos++;
             if (m_pos >= m_size) {
                 m_pos = 0;
-            }  // loop if reached the end of the stored values
+            }
 
             m_sumVal -= (CalcType)m_lastVals[m_pos];  // Subtract the oldest value
             m_lastVals[m_pos] = valBuff[buffPos];     // Store the new value

firmware/common/dsp_iir_config.hpp

@@ -38,9 +38,7 @@ constexpr iir_biquad_config_t audio_48k_hpf_300hz_config{
 // scipy.signal.butter(2, 300 / 12000.0, 'highpass', analog=False)
 constexpr iir_biquad_config_t audio_24k_hpf_300hz_config{
     {0.94597686f, -1.89195371f, 0.94597686f},
-    {1.00000000f, -1.88903308f, 0.89487434f}
-
-};
+    {1.00000000f, -1.88903308f, 0.89487434f}};
 
 // scipy.signal.butter(2, 30 / 12000.0, 'highpass', analog=False)
 constexpr iir_biquad_config_t audio_24k_hpf_30hz_config{

firmware/common/pocsag.cpp

@@ -225,30 +225,14 @@ void pocsag_encode(const MessageType type, BCHCode& BCH_code, const uint32_t fun
     } while (char_idx < message_size);
 }
 
-// -------------------------------------------------------------------------------
-// Get the number of bits that differ between the two values.
-// -------------------------------------------------------------------------------
-inline uint8_t bitsDiff(unsigned long left, unsigned long right) {
-    unsigned long xord = left ^ right;
-    uint8_t count = 0;
-
-    for (int i = 0; i < 32; i++) {
-        if ((xord & 0x01) == 1) ++count;
-        xord = xord >> 1;
-    }
-
-    return (count);
+// ----------------------------------------------------------------------------
+// EccContainer
+// ----------------------------------------------------------------------------
+EccContainer::EccContainer() {
+    setup_ecc();
 }
 
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-static uint32_t ecs[32]; /* error correction sequence */
-static uint32_t bch[1025];
-static int eccSetup = 0;
-
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-void setupecc() {
+void EccContainer::setup_ecc() {
     unsigned int srr = 0x3b4;
     unsigned int i, n, j, k;
 
@@ -311,23 +295,12 @@ void setupecc() {
     }
 }
 
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-inline int errorCorrection(uint32_t& val) {
-    // Set up the tables the first time
-    if (eccSetup == 0) {
-        setupecc();
-        eccSetup = 1;
-    }
-
+int EccContainer::error_correct(uint32_t& val) {
     int i, synd, errl, acc, pari, ecc, b1, b2;
 
     errl = 0;
     pari = 0;
 
-    /* run through error detection and correction routine */
-
-    // for (i=0; i<=20; i++)
     ecc = 0;
     for (i = 31; i >= 11; --i) {
         if (val & (1 << i)) {
@@ -336,7 +309,6 @@ inline int errorCorrection(uint32_t& val) {
         }
     }
 
-    // for (i=21; i<=30; i++)
     acc = 0;
     for (i = 10; i >= 1; --i) {
         acc = acc << 1;
@@ -390,8 +362,8 @@ bool pocsag_decode_batch(const POCSAGPacket& batch, POCSAGState& state) {
 
         // Error correct twice. First time to fix any errors it can,
         // second time to count number of errors that couldn't be fixed.
-        errorCorrection(codeword);
-        auto error_count = errorCorrection(codeword);
+        state.ecc->error_correct(codeword);
+        auto error_count = state.ecc->error_correct(codeword);
 
         switch (state.mode) {
             case STATE_CLEAR:

firmware/common/pocsag.hpp

@@ -56,23 +56,46 @@ enum MessageType : uint32_t {
     ALPHANUMERIC
 };
 
+/* Holds error correction arrays. This allows the arrays to
+ * be freed when POCSAG is not running, saving ~4kb of RAM. */
+class EccContainer {
+   public:
+    EccContainer();
+
+    EccContainer(const EccContainer&) = delete;
+    EccContainer(EccContainer&&) = delete;
+    EccContainer& operator=(const EccContainer&) = delete;
+    EccContainer& operator=(EccContainer&&) = delete;
+
+    int error_correct(uint32_t& val);
+
+   private:
+    void setup_ecc();
+
+    /* error correction sequence */
+    uint32_t ecs[32];
+    uint32_t bch[1025];
+};
+
 struct POCSAGState {
-    uint8_t codeword_index;
-    uint32_t function;
-    uint32_t address;
+    EccContainer* ecc = nullptr;
+    uint8_t codeword_index = 0;
+    uint32_t function = 0;
+    uint32_t address = 0;
     Mode mode = STATE_CLEAR;
     OutputType out_type = EMPTY;
-    uint32_t ascii_data;
-    uint32_t ascii_idx;
-    uint32_t errors;
-    std::string output;
+    uint32_t ascii_data = 0;
+    uint32_t ascii_idx = 0;
+    uint32_t errors = 0;
+    std::string output{};
 };
 
 const pocsag::BitRate pocsag_bitrates[4] = {
     pocsag::BitRate::FSK512,
     pocsag::BitRate::FSK1200,
     pocsag::BitRate::FSK2400,
-    pocsag::BitRate::FSK3200};
+    pocsag::BitRate::FSK3200,
+};
 
 std::string bitrate_str(BitRate bitrate);
 std::string flag_str(PacketFlag packetflag);