!CWKeying.ipynb

cw_keying_2.py

import numpy as np
import simpleaudio as sa
import time

# Set up audio params
sample_rate = 8000
sound_length = 5 #seconds
t = np.linspace(0, sound_length, sound_length * sample_rate, False)

# Define CW signal
wave1_freq = 600
wave1_amplitude = 1
wave1_phi = 0
wave1 = wave1_amplitude * np.sin(wave1_freq * t * 2 * np.pi + wave1_phi)

# Create keying waveform
wpm = 40
tx_intv = 1.2 / wpm # keying interval

keying = np.zeros(wave1.size)
for i in range (1, int((keying.size / sample_rate) / (tx_intv)), 2):
    keying[int(sample_rate * (i * tx_intv)):int(sample_rate * (i * tx_intv  + tx_intv))] = 1

taps = np.array([
  -0.005946901269245122, \
  -0.0032211059347523195, \
  -0.0038440699902768383, \
  -0.004335185893314178, \
  -0.004618082667223961, \
  -0.004610544806595846, \
  -0.004229573289430787, \
  -0.0033917453968697483, \
  -0.002028051041620645, \
  -0.0000779737869300087, \
  0.0024926916286312248, \
  0.00569982765877049, \
  0.009534812572960348, \
  0.013961833701309628, \
  0.018917781140524174, \
  0.024309521855601125, \
  0.030016610101736976, \
  0.03589781173597167, \
  0.04180040186066688, \
  0.047555344979786536, \
  0.05298415762863876, \
  0.05792015092713824, \
  0.06221396733171683, \
  0.06570516590449127, \
  0.06829411291109369, \
  0.069881349050518, \
  0.07041715978547827, \
  0.069881349050518, \
  0.06829411291109369, \
  0.06570516590449127, \
  0.06221396733171683, \
  0.05792015092713824, \
  0.05298415762863876, \
  0.047555344979786536, \
  0.04180040186066688, \
  0.03589781173597167, \
  0.030016610101736976, \
  0.024309521855601125, \
  0.018917781140524174, \
  0.013961833701309628, \
  0.009534812572960348, \
  0.00569982765877049, \
  0.0024926916286312248, \
  -0.0000779737869300087, \
  -0.002028051041620645, \
  -0.0033917453968697483, \
  -0.004229573289430787, \
  -0.004610544806595846, \
  -0.004618082667223961, \
  -0.004335185893314178, \
  -0.0038440699902768383, \
  -0.0032211059347523195, \
  -0.005946901269245122])

# Execute the filter
filtered_keying = np.zeros(keying.size - taps.size)
for i in range(filtered_keying.size):
    filtered_keying[i] = np.inner(taps, keying[taps.size + i:i:-1])

signal = wave1 * keying
output = wave1[taps.size:] * filtered_keying

# Normalize audio level to 16 bit int for simpleaudio
signal *= 32767 / np.max(np.abs(signal))
signal = signal.astype(np.int16)

# Start playback then wait for finish
play_obj = sa.play_buffer(signal, 1, 2, sample_rate)
play_obj.wait_done()

# # Now wait one second
time.sleep(1)

# Normalize audio level to 16 bit int for simpleaudio
output *= 32767 / np.max(np.abs(output))
output = output.astype(np.int16)

# Start playback then wait for finish
play_obj = sa.play_buffer(output, 1, 2, sample_rate)
play_obj.wait_done()