Python Morse Code Generator

 

#!/usr/bin/python

"""
Morse Code Generator. Geoff Robinson, G4AKW, Version 1.0, 4th December 2011.
Requirements: Python 2.7, Linux OS, alsaaudio.
Usage # python mainmorse.py 

The basic element of Morse code is the dot and all other elements can be defined in terms of multiples of the dot length. The word PARIS is used because this is the length of a typical word in English plain text, it has a total length of 50 dot lengths. If the word PARIS is sent ten times in a minute using normal Morse code timing then the code speed is 10 WPM.

There are 500 dot lengths in a minute for 10 wpm or 1000 dot lengths per min for 20 wpm.
The dot length is therefore 60mS for 20 wpm. The python dictionary 'code'  and the function convert() converts
characters to their dot space equivalents i.e either on or off keying. 

"""
import serial
import time, thread
import random
import sys

import sched
import wave, struct, math
from alsaaudio import *
import signal

def convert(msg):
 """  Take msg and convert it to the correct True or False dot interval values."""
 global start, morselist

 code = {'a':'. ...','b':'... . . .','c':'... . ... .','d':'... . .','e':'.',
              'f':'. . ... .','g':'... ... .','h':'. . . .','i':'. .','j':'. ... ... ...',
              'k':'... . ...','l':'. ... . .','m':'... ...','n':'... .','o':'... ... ...',
              'p':'. ... ... .','q':'... ... . ...','r':'. ... .','s':'. . .','t':'...',
              'u':'. . ...','v':'. . . ...','w':'. ... ...','x':'... . . ...',
              'y':'... . ... ...','z':'... ... . .','1':'. ... ... ... ...','2':'. . ... ... ...',
              '3':'. . . ... ...','4':'. . . . ...','5':'. . . . .','6':'... . . . .',
              '7':'... ... . . .','8':'... ... ... . .','9':'... ... ... ... .',
              '0':'... ... ... ... ...',' ':' '}


 """ next we go character by character through the message and add in the correct spacing""" 
 
 for ch in msg: 
  
  morse = ''
  if ch == ' ':
   morse = morse + '    ' # 4 spaces plus 3 below = 7 for space
  else:  
   morse = morse + code[ch]
   morse = morse + '   ' # 3 spaces between chars 
   
  for ch1 in morse:
   if ch1 == '.':
    ch1 = True
   else: 
    ch1 = False
   morselist.append(ch1) # morselist is the input buffer
 
 start = 1  



def catcher(signum, _):
 """This is the handler function for the SIGALRM interupt which is generated every dot interval """
 global c,z,morselist,start 
 
 if c != 0:  # if c!=0 a dah is sounding so skip this function for 3 dot intervals
  c = c - 1
  return
 else:
  if (start == 1) and (z < len (morselist)): # check input buffer end not reached

  
   if morselist[z] and morselist[z+1]: # detect a dah
    z = z + 3
    c = 3
    out_dah.write(s_dah)
   
   elif morselist[z]:   # detect a dit
    z += 1
    out_dit.write(s_dit)
   else:     # detect a space
    z += 1

  else:
   return
  return


def mysound(freq, dur) :
 """ Function sounds a freq (Hz) sinusoid with dur (mS) length """

 global s_dit, s_dah, out_dit, out_dah, period_dit, period_dah

 
 rate = 44100    # frame rate
 period_dit = int(dur * 44) # number of frames (44 frames per mS)(slightly less)
 period_dah = int(dur * 44 * 3)

 sig_dit = [ math.sin( 2.0*math.pi*freq*x/rate ) for x in range(period_dit) ]
 sig_dah = [ math.sin( 2.0*math.pi*freq*x/rate ) for x in range(period_dah) ]

 # The scale factor for 32bit resolution

 scale = ( 2**32 - 1 )/2.0

 # Scale the signal list
 sig_32dit = [ int(scale*x) for x in sig_dit ]
 sig_32dah = [ int(scale*x) for x in sig_dah ]

 # sound card device initialization
 out_dit = PCM(type=PCM_PLAYBACK, mode=PCM_NONBLOCK, card='default')
 out_dah = PCM(type=PCM_PLAYBACK, mode=PCM_NONBLOCK, card='default')

 # parameters
 channels = 1
 out_dit.setchannels(channels)
 out_dah.setrate(rate)
 out_dah.setchannels(channels)
 out_dit.setrate(rate)


 # Signed 32 bit samples for each channel (Little Endian byte order)
 out_dit.setformat(PCM_FORMAT_S32_LE)
 out_dah.setformat(PCM_FORMAT_S32_LE)
 out_dit.setperiodsize(period_dit)
 out_dah.setperiodsize(period_dah)

 s_dit=struct.pack('<'+channels*period_dit*'l',*sig_32dit)
 s_dah=struct.pack('<'+channels*period_dah*'l',*sig_32dah) 
 
 # l is long integer size=4 pack requires (88100 times ?) arguments

 # use out_dit.write(s_dit) for dit sound
 # use out_dah.write(s_dah) for dah sound


def main():

 global morselist,y,w,z,c,start

 if (len(sys.argv) > 1):
  speed = sys.argv[1]
          print "The speed is set to", speed, "wpm"

 else:
  speed = 20
  print "The default speed is", speed, "wpm"
  
 y = int (speed)
 x = (1200/y)  # x is dot interval in mS
 w = x/1000.0 # w is dot interval in sec
 z = 0
 c = 0
 start = 0

 
 mysound (800, x) # Sound frequency set to 800Hz

 morselist = []

 signal.signal(signal.SIGALRM, catcher) # Set the handler for signal.SIGALRM to the function catcher.
 signal.setitimer(signal.ITIMER_REAL, w, w) #This timer sends a SIGALRM signal every dot interval.

 a = "_"
 print 'On a newline type cr to end input: '
 while a != '':
 
  try:
   a = raw_input()
 
  except EOFError:  # needed as SIGALRM interupts keyboard input
   
   continue

  
  a = a.lower()
  convert(a)  

main()