do averaging over one second for the signal stregth

README.md

@@ -40,7 +40,7 @@ Therefore this application supports multiple stages of decimation.
 The config has mandatory global arguments `CenterFrequency`, `DeviceString` and `SampleRate` for the SDR.
 The optional argumens `RFGain`, `IFGain` and `BBGain` are for setting the gains of the SDR, by default these are zero.
 
-Specify an optional table with the name `Prometheus` and the values `Host`, `Port` and `PollInterval` to send metrics about the currently received signal strength to a prometheus server.
+Specify an optional table with the name `Prometheus` and the values `Host` and `Port` to send metrics about the currently received signal strength to a prometheus server.
 
 If a table specifies `Frequency`, `Host` and `Port`, the signal is directly decoded from the SDR.
 If it is specified in a subtable, it is decoded from the decimated signal described by the associtated table.
@@ -58,7 +58,6 @@ BBGain = unsigned int (default 0)
 [Prometheus]
 Host = "string" (default 127.0.0.1)
 Port = unsigned int (default 9010)
-PollInterval = unsigned int (in seconds)
 
 [DecimateA]
 Frequency = unsigned int

include/config.h

@@ -148,19 +148,15 @@ class Prometheus {
   const std::string host_;
   /// the port to which prometheus is sending data to
   const uint16_t port_;
-  /// the polling interval of prometheus
-  unsigned int polling_interval_;
 
   Prometheus() = delete;
 
   /// The prometheus exporter to we want to send the metrics
   /// \param host the host to which prometheus is sending data
   /// \param port the port to which prometheus is sending data
-  /// \param polling_interval the interval at which data is sent
-  Prometheus(std::string host, const uint16_t port, const unsigned polling_interval)
+  Prometheus(std::string host, const uint16_t port)
       : host_(std::move(host))
-      , port_(port)
-      , polling_interval_(polling_interval){};
+      , port_(port){};
 };
 
 class TopLevel {
@@ -222,9 +218,8 @@ template <> struct from<std::unique_ptr<config::Prometheus>> {
   static auto from_toml(const value& v) -> std::unique_ptr<config::Prometheus> {
     const std::string prometheus_host = find_or(v, "Host", config::kDefaultPrometheusHost);
     const uint16_t prometheus_port = find_or(v, "Port", config::kDefaultPrometheusPort);
-    const unsigned int polling_interval = find<unsigned int>(v, "PollInterval");
 
-    return std::make_unique<config::Prometheus>(prometheus_host, prometheus_port, polling_interval);
+    return std::make_unique<config::Prometheus>(prometheus_host, prometheus_port);
   }
 };
 

src/tetra-receiver.cpp

@@ -50,8 +50,6 @@ class ApplicationData {
   gr::top_block_sptr tb = nullptr;
   /// the optional prometheus exporter
   std::shared_ptr<PrometheusExporter> exporter = nullptr;
-  /// the polling interval of the exporter
-  unsigned int polling_interval = 0;
 };
 
 class GnuradioBuilder {
@@ -111,14 +109,12 @@ class GnuradioBuilder {
           {{"frequency", std::to_string(stream.spectrum_.center_frequency_)}, {"name", stream.name_}});
 
       auto mag_squared = gr::blocks::complex_to_mag_squared::make();
-      // low pass filter the signal based on the polling interval so we adhear to nyquist
-      double cutoff_freq = 1.0 / static_cast<double>(2 * app_data.polling_interval);
-      auto downsampler_taps =
-          gr::filter::firdes::low_pass(/*gain=*/1.0, /*sampling_freq=*/stream.spectrum_.sample_rate_,
-                                       /*cutoff_freq=*/cutoff_freq, /*transition_width=*/cutoff_freq * 0.2);
+      // averaging filter over one second
+      unsigned tap_size = stream.spectrum_.sample_rate_;
+      std::vector<float> averaging_filter(/*count=*/tap_size, /*alloc=*/1.0 / tap_size);
       // do not decimate directly to the final frequency, since there will be some jitter
-      unsigned decimation = stream.spectrum_.sample_rate_ * app_data.polling_interval / 10;
-      auto fir = gr::filter::fir_filter_fff::make(/*decimation=*/decimation, downsampler_taps);
+      unsigned decimation = tap_size / 10;
+      auto fir = gr::filter::fir_filter_fff::make(/*decimation=*/decimation, averaging_filter);
       auto populator = gr::prometheus::PrometheusGaugePopulator::make(/*gauge=*/stream_signal_strength);
 
       tb->connect(xlat, 0, mag_squared, 0);
@@ -161,7 +157,6 @@ class GnuradioBuilder {
     if (top.prometheus_) {
       std::string prometheus_addr = top.prometheus_->host_ + ":" + std::to_string(top.prometheus_->port_);
       app_data.exporter = std::make_shared<PrometheusExporter>(prometheus_addr);
-      app_data.polling_interval = top.prometheus_->polling_interval_;
     }
 
     // setup osmosdr source

test/config_test.cpp

@@ -101,7 +101,6 @@ TEST(config /*unused*/, TopLevel_prometheus_default /*unused*/) {
 		SampleRate = 60000
 		
 		[Prometheus]
-		PollInterval = 10
 	)"_toml;
 
   const config::TopLevel t = toml::get<config::TopLevel>(config_object);
@@ -111,7 +110,6 @@ TEST(config /*unused*/, TopLevel_prometheus_default /*unused*/) {
 
   EXPECT_EQ(t.prometheus_->host_, config::kDefaultPrometheusHost);
   EXPECT_EQ(t.prometheus_->port_, config::kDefaultPrometheusPort);
-  EXPECT_EQ(t.prometheus_->polling_interval_, 10);
 }
 
 TEST(config /*unused*/, TopLevel_prometheus_set /*unused*/) {
@@ -123,7 +121,6 @@ TEST(config /*unused*/, TopLevel_prometheus_set /*unused*/) {
 		[Prometheus]
 		Host = "127.0.0.2"
 		Port = 4200
-		PollInterval = 20
 	)"_toml;
 
   const config::TopLevel t = toml::get<config::TopLevel>(config_object);
@@ -133,7 +130,6 @@ TEST(config /*unused*/, TopLevel_prometheus_set /*unused*/) {
 
   EXPECT_EQ(t.prometheus_->host_, "127.0.0.2");
   EXPECT_EQ(t.prometheus_->port_, 4200);
-  EXPECT_EQ(t.prometheus_->polling_interval_, 20);
 }
 
 TEST(config /*unused*/, TopLevel_valid_parser /*unused*/) {