I try do dedodulate a signal, saved in complex64 in a .brut file. I have 2 functions, one to automatically identify the frequencies and the other to demodulate, based on the frequencies detected.

Here the code :

import numpy as np
import matplotlib.pyplot as plt
from scipy.signal import find_peaks
from tkinter import filedialog

def estimate_frequencies(signal, fs, niveau_fsk):
    fft_result = np.fft.fft(signal)
    fft_freq = np.fft.fftfreq(len(signal), 1/fs)

    half_spectrum = fft_result[:len(fft_result)//2]
    half_freqs = fft_freq[:len(fft_freq)//2]

    peaks, _ = find_peaks(np.abs(half_spectrum), height=np.max(np.abs(half_spectrum))/10)
    peaks = peaks[half_freqs[peaks] > 0]

    important_peaks = np.argsort(-np.abs(half_spectrum[peaks]))[:niveau_fsk]
    estimated_freqs = half_freqs[peaks[important_peaks]]

    return estimated_freqs

def demodulate_fsk(signal, fs, freqs, symbol_duration):
    instantaneous_phase = np.angle(signal)
    instantaneous_frequency = np.diff(instantaneous_phase) * fs / (2.0 * np.pi)

    decoded_bits = []
    step_size = int(symbol_duration * fs)
    for i in range(0, len(instantaneous_frequency), step_size):
        segment = instantaneous_frequency[i:i+step_size]
        mean_freq = np.mean(segment)
        distances = [abs(mean_freq - f) for f in freqs]
        decoded_bits.append(np.argmin(distances))
    
    return np.array(decoded_bits)

filename = filedialog.askopenfilename(title="Selection d'un fichier IQ")
signal = np.fromfile(filename, dtype=np.int16).astype(np.float32).view(npplex64)

fs = 46242 # I use the bandwith of my signal
niveau_fsk = 2
symbol_duration = 1 / 19608.5 # Modulation speed = 19608.5 Bd

freqs = estimate_frequencies(signal, fs, niveau_fsk)
print("Fréquences estimées :", freqs)

decoded_bits = demodulate_fsk(signal, fs, freqs, symbol_duration)
print(decoded_bits)

The problem is that frequencies don't seem to be properly detected, and the demodulation doesn't work as expected (the binary train is wrong).