connect to fldigi via xml-rpc, get the current dial and log frequency, use it to retune the radio to keep the audio frequency at a set point

fldigi_autotuner.py

"""
fldigi autotuner script
Released into the public domain by Adam Greig in 2010
"""

import xmlrpclib
import math
import time

# Desired audio frequency (Hz)
demand_freq = 1500

# Loop time (s)
loop_time = 0.1

# The highest step change we will retune the radio by (Hz/loop)
max_change = 3

# How quickly we react to errors. Too high will cause oscillation.
error_gain = 0.1

# Connect to fldigi
s = xmlrpclib.ServerProxy("http://localhost:7362")

while 1:
    # Read current dial and signal frequencies
    dial_freq = s.main.get_frequency()
    signal_freq = float(s.log.get_frequency()) * 1000

    # Audio frequency is the difference between the two
    audio_freq = signal_freq - dial_freq

    # Calculate error in audio frequency
    freq_error = demand_freq - audio_freq
    freq_error *= error_gain

    # Change by max_change at most
    if freq_error > max_change:
        freq_error = max_change
    elif freq_error < -max_change:
        freq_error = -max_change

    # Set new frequency
    new_freq = dial_freq - freq_error
    s.main.set_frequency(new_freq)

    # Output info
    print "Dial", int(dial_freq)
    print "Signal", int(signal_freq)
    print "Audio", int(audio_freq)
    print "Error", int(1500 - audio_freq)
    print "Change", int(freq_error)
    print "New Frequency", int(new_freq)
    print

    # Sleep a bit
    time.sleep(loop_time)