End sem 7; week 2 winter session 2025

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

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+import numpy as np
+import scipy as sp
+from threading import Thread
+import time
+import queue
+
+import matplotlib.animation as animation
+import matplotlib.pyplot as plt
+
+from rtlsdr import RtlSdr
+
+import dsp
+
+
+class GFSKDemod: 
+    def __init__(self, sdr:RtlSdr, baud_rate:int=9600, num_samples:int=512):
+        self.sdr = sdr
+        self.baud_rate = baud_rate
+        self.num_samples = num_samples
+        self.fig, self.ax = plt.subplots()
+
+        self.duration = self.num_samples/self.sdr.sample_rate
+
+    # Demodulate an update the sound buffer
+    def _demod(self, samples):
+        message = dsp.quad_demod(samples)
+        message = dsp.lowpass(message, 16E3, self.sdr.sample_rate)
+        #message /= np.max(np.abs(message))
+        #message = message.astype(np.float32)
+        time = len(message)*self.sdr.sample_rate
+        t = np.linspace(0,time,len(message))
+        return t, message
+
+
+    # Begin reading and demodulation
+    async def start(self):
+        plt.ion()
+        plt.show()
+
+        async for samples in self.sdr.stream(self.num_samples):
+            self.ax.clear()
+            t, message = self._demod(samples)
+
+            #num_samples = int(len(message)*self.resample_rate/self.sdr.sample_rate)
+            #message = sp.signal.resample(message, num_samples)
+
+            #t = np.linspace(0,1,len(message))*t[:-1]
+            #self.ax.plot(t,message)
+            #spectrum = np.abs(sp.fft.fftshift(sp.fft.fft(samples)))**2
+            #spectrum_db = dsp.db(spectrum)
+            #self.ax.plot(spectrum_db)
+
+            self.fig.canvas.draw()
+            self.fig.canvas.flush_events()
+
+
+    def stop(self):
+        self.sdr.cancel_read_async()