A very unusual Python program...

Bazza — Tue Nov 01, 2011 11:16 pm

Author: Bazza

Posted: Tue Nov 01, 2011 11:16 pm

Hi all...

The code just about says it all, for Python 3.x.x...

It is a <50 Hz to >3500 Hz audio frequency counter with the ability
to go to an even much greater range with simple home brew electronics...

Intended for the youngster to understand as well as the experts.

Be aware of word wrapping etc...

Enjoy finding simple solutions to often very difficult problems... ;o)

Bazza...

Code:

# Freq_Counter3x.py...
#
# A DEMO audio frequency counter using standard text mode Python.
# (C)2011, B.Walker, G0LCU. Issued as Public Domain EXCLUSIVELY to LXF.
#
# "/dev/dsp" is required for this to work. If it doesn't exist install
# "oss-compat" from your distro's repository.
# Written in such a way that youngsters can understand what is going on.
#
# Tested on PCLinuxOS 2009 and Debian 6.0.0 using Python versions
# 3.0.1, 3.1.3 and 3.2.2.
#
# It will display from <50 Hz to >3500 Hz to withing 0.1% accuracy.
# With a very simple external hardware add-on AND sine wave, <10 Hz to
# >35 KHz is well within this DEMOs scope; however for this DEMO only a
# simple connecting cable is needed. This is yet another ultra simple
# piece of audio test gear that can be made and understood by a 10 year
# old...
# See my other DEMO uploads of very basic test gear using the sound card
# as the prime mover:-
#
# http://code.activestate.com/recipes/users/4177147/
#
# ENJOY...
#
# Bzzza, G0LCU...

def main():
# Make variables global; my choice... ;o)
global record
global n
global freq
# Set the startup values...
freq=0
record=""
n=0
# Connect a 3.2mm jack plugs stereo cable from the audio output to
# the microphone input; or from a sine/square generator into the
# microphone input.
#
# Using the 1 KHz Audio Function Generator, (found elsewhere on this site),
# from another Python shell start up this code and generate a square,
# triangle or sine wave.
# Enter a continuous loop.
# Grab a file from my Laptop`s, Notebook`s and Netbook`s microphone socket.
while 1:
   # Do a 1 second recorded burst...
   audio=open('/dev/dsp', 'rb')
   # "record" is the string to be counted...
   record=audio.read(8000)
   audio.close()
   # Enter another loop to do the count...
   n=0
   freq=0
   while 1:
      # Assume a square wave "mark to space" ratio of 1 to 1 is used,
      # then wait until a "space" is found.
      # This ensures that the loop cycles when NO input is
      # applied to the microphone socket.
      # Exit this loop when "mark" is found or n=8000...
      while record[n]<=127:
         n=n+1
         # Ensure as soon as n=8000 occurs it drops out of the loop.
         if n>=8000: break
      # Ensure as soon as n=8000 occurs it drops completely out of this loop.
      if n>=8000: break
      # Now the "mark" can loop until a "space" is found again and the whole
      # can cycle until n=8000...
      while record[n]>=128:
         n=n+1
         # Ensure as soon as n=8000 occurs it drops out of the loop.
         if n>=8000: break
      # Ensure as soon as n=8000 occurs it drops completely out of this loop.
      if n>=8000: break
      # This will become the frequency of a symmertical waveform
      # when the above loops are finally exited...
      freq=freq+1
   # An ultra simple clear screen line...
   # This line is not needed for the demo but added for fullness...
   print("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n")
   # Now display the value in the same place on screen every time.
   # This assumes a 24 or 25 line Python Shell window. Just modify to
   # suit your particular Shell that you use...
   print("\nA simple 50 Hz to 3500 Hz audio frequency counter.\n")
   print("(C)2011, B.Walker, G0LCU. Issued as Public Domain.\n")
   print("Accuracy is within 0.1% of the displayed frequency...\n")
   print("\n\nFrequency is", freq, "Hz...\n\n\n\n\n\n\n\n\n\n\n\n\n")
main()
# End of Freq_Counter.py DEMO.
# Enjoy finding simple solutions to often very difficult problems.

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A very unusual Python program...