DSLWP-B waterfall script

waterfall_dslwp.py

#!/usr/bin/env python3

import numpy as np
from scipy.fftpack import fft, fftshift
from scipy.signal import blackman
import matplotlib.pyplot as plt

# Parameters

N = 2**13
averaging = 4

samp_rate = 40000
freq = 2400
span = 1000

hz_per_bin = samp_rate/N
centre_bin = int(np.round(freq/hz_per_bin))
span_bin = int(np.ceil(span/hz_per_bin))

samples = np.fromfile('/tmp/dslwp_photo.c64', dtype=np.complex64)

total_transforms = len(samples)//(N//2) - 1
lines = total_transforms//averaging

window = blackman(N)

waterfall = np.empty((lines, 2*span_bin), dtype=np.float32)

for line in range(lines):
    transforms = np.zeros((averaging, 2*span_bin), dtype=np.float32)
    for transform in range(averaging):
        start = (line * averaging + transform)*N//2
        x = samples[start : start+N]
        f = fft(x * window)[centre_bin - span_bin : centre_bin + span_bin]
        transforms[transform,:] = np.real(f)**2 + np.imag(f)**2
        waterfall[line,:] = 10*np.log10(np.average(transforms, axis=0)) - 20*np.log10(N)

plt.imsave('dslwp.png', waterfall[:,::-1].T, vmin = -125, vmax=-95, cmap='viridis', origin='bottom')