End sem 7; week 2 winter session 2025

7th-Semester-Fall-2024/ECOMMS/final-project/bfm_demod.py

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+import numpy as np
+import scipy as sp
+import sounddevice as sd
+from threading import Thread
+import time
+import queue
+
+import matplotlib.animation as anim
+import matplotlib.pyplot as plt
+
+from rtlsdr import RtlSdr
+import asyncio
+import dsp
+
+class BfmDemod: 
+    def __init__(self, sdr:RtlSdr, stream:sd.OutputStream, audio_sample_rate:int=48000, num_samples:int=8192):
+        self.sdr = sdr
+        self.stream = stream
+        self.audio_sample_rate = audio_sample_rate
+        self.buffer = queue.Queue(10)
+        self.num_samples = num_samples
+
+        self.fig, self.ax = plt.subplots()
+        self.duration = self.num_samples/self.sdr.sample_rate
+        #lower_extent = self.sdr.center_freq - self.sdr.sample_rate/2
+        #upper_extent = self.sdr.center_freq + self.sdr.sample_rate/2
+
+        #self.fig, self.ax = plt.subplots()
+        #self.ax.xlabel = "Frequency [Hz]"
+        #self.ax.ylabel = "Amplitude [dB]"
+        #self.ax.set_xlim(left=lower_extent, right=upper_extent)
+    
+    # Plot the spectrum of the incoming samples
+    def _spectrum_update(self, frame):
+        self.ax.clear()
+        if self.buffer is not None:
+            spectrum = np.abs(sp.fft.fftshift(sp.fft.fft(self.buffer)))**2
+            spectrum_db = dsp.db(spectrum)
+            self.ax.plot(spectrum_db)
+        return self.ax,
+
+    # Begin reading and demodulation
+    async def start(self):
+        self.stream.start()
+        plt.ion()
+        self.scatter = self.ax.scatter([], [])
+        plt.show()
+
+        async for samples in self.sdr.stream(self.num_samples):
+            message = dsp.quad_demod(samples)
+            message = dsp.lowpass(message, 16E3, self.sdr.sample_rate)
+            message /= np.max(np.abs(message))
+            
+            time = len(message)/self.sdr.sample_rate
+            num_samples = int(time*self.audio_sample_rate)
+            message = sp.signal.resample(message, num_samples)
+
+            message = message.astype(np.float32)
+            #self.stream.write(message)
+
+            spectrum = np.abs(sp.fft.fftshift(sp.fft.fft(samples)))**2
+            spectrum_db = dsp.db(spectrum)
+            self.ax.clear()
+            self.ax.plot(spectrum_db)
+
+            self.ax.relim()
+            self.ax.autoscale_view()
+
+            self.fig.canvas.draw()
+            self.fig.canvas.flush_events()
+
+        await sdr.stop()
+        
+
+    def stop(self):
+        self.sdr.cancel_read_async()
+        self.reader.join()
+        self.stream.stop()
+
+