Added comments for utils class

gnuradio/gr-dji_droneid/include/gnuradio/dji_droneid/utils.h

@@ -24,18 +24,61 @@ namespace dji_droneid {
 class DJI_DRONEID_API utils
 {
 public:
-    utils();
-    ~utils();
+    utils() = default;
+    ~utils() = default;
 
+    // Hz between each carrier in DroneID
     static constexpr float CARRIER_SPACING = 15e3;
-    static constexpr uint32_t DATA_CARRIER_COUNT = 600;
-    static constexpr std::complex<float> I = std::complex<float>(0, 1);
 
+    // Number of OFDM data carriers in DroneID (independent of sample rate)
+    static constexpr uint32_t DATA_CARRIER_COUNT = 600;
+
+    /**
+     * Get the correct FFT size based on the sample rate
+     * @param sample_rate Sample rate (in Hz) of the collected samples
+     * @return Number of FFT bins required
+     */
     static uint32_t get_fft_size(float sample_rate);
+
+    /**
+     * Get the correct sample rate based on the FFT size
+     * @param fft_size Number of FFT bins
+     * @return Sample rate (in Hz)
+     */
     static float get_sample_rate(uint32_t fft_size);
+
+    /**
+     * Get a list of FFT bins (all positive, assuming that DC is in the middle) that should be used as data carriers
+     * @param sample_rate Sample rate (in Hz)
+     * @return List of utils::DATA_CARRIER_COUNT values denoting position of all data carriers
+     */
     static std::vector<uint32_t> get_data_carrier_indices(float sample_rate);
+
+    /**
+     * Create a Zadoff Chu sequence of `length` elements using the root index `root`
+     * @param root Root index
+     * @param length Number of elements to create
+     * @return Vector of complex floats
+     */
     static std::vector<std::complex<float>> zadoff_chu(uint32_t root, uint32_t length);
+
+    /**
+     * Create a time domain ZC sequence for the specified OFDM symbol index (4 or 6)
+     *
+     * Will be `fft_size` elements long
+     *
+     * <b>This only currently works for drones that have two ZC sequences present!!!</b>
+     * @param fft_size Number of FFT bins the sequence should be generated for
+     * @param symbol_idx Symbol index to generate the sequence for (must be 4 or 6)
+     * @return Complex float vector of `fft_bins` elements representing the gold ZC sequence in the time domain
+     */
     static std::vector<std::complex<float>> create_zc(uint32_t fft_size, uint8_t symbol_idx);
+
+    /**
+     * Get the long and short cyclic prefix lengths for the provided sample rate
+     * @param sample_rate Sample rate (in Hz)
+     * @return Pair with the first element being the long cyclic prefix length in samples, second being the short
+     */
     static std::pair<uint16_t, uint16_t> get_cyclic_prefix_lengths(float sample_rate);
 
 private:
@@ -44,6 +87,4 @@ private:
 } // namespace dji_droneid
 } // namespace gr
 
-
-
 #endif /* INCLUDED_DJI_DRONEID_UTILS_H */