Simple GNU Radio embedded python block implementation of this: https://github.com/nootedandrooted/rtl-sdr-close-call-monitor
 

 

 

"""
Embedded Python Blocks:

Each time this file is saved, GRC will instantiate the first class it finds
to get ports and parameters of your block. The arguments to __init__  will
be the parameters. All of them are required to have default values!
"""

import numpy as np
import time
from gnuradio import gr

class blk(gr.sync_block):  # other base classes are basic_block, decim_block, interp_block

    def __init__(self, center_freq = 433920000, sample_rate = 250000, sql_level = -20):  # only default arguments here
        """arguments to this function show up as parameters in GRC"""
        gr.sync_block.__init__(
            self,
            name='Embedded Python Block',   # will show up in GRC
            in_sig=[np.complex64],
            out_sig=[np.float32]
        )
        # if an attribute with the same name as a parameter is found,
        # a callback is registered (properties work, too).
        # self.example_param = example_param
        self.center_freq = center_freq
        self.sample_rate = sample_rate
        self.start_freq = center_freq - sample_rate/2
        self.end_freq = center_freq + sample_rate/2
        self.sql_level = sql_level

    def work(self, input_items, output_items):
        samples = input_items[0]
        freq_range = np.linspace(self.start_freq, self.end_freq, len(samples), endpoint=False)
        spectrum = np.abs(np.fft.fftshift(np.fft.fft(samples)))
        peak_index = np.argmax(spectrum)
        peak_freq = freq_range[peak_index]
        if spectrum[peak_index] > self.sql_level:
         output_items[0][:] = peak_freq
        else:
         output_items[0][:] = 0
        return len(output_items[0])