I had no idea what this data was. I thus found myself reading a writeup of the year before
Once i had understood how this I2C works i went to writing the program to parse the data and extract the flag : extract.py
import json
import sys
from pyDigitalWaveTools.vcd.parser import VcdParser
The code in craft_signal.py applies the inverse Fourier Transform on the bytes it reads from the flag.txt. So we only need to apply the Fourier Transform on the fftea data. This code thus recovers the flag :
import numpy as np
# Load the data from the "fftea" file
data = np.fromfile("challenge", dtype = np.complex64)
data = np.fromfile("fftea", dtype = np.complex64)