147 lines
4.9 KiB
C++
147 lines
4.9 KiB
C++
// morse.hxx -- Morse code generation class
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//
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// Written by Curtis Olson, started March 2001.
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//
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// Copyright (C) 2001 Curtis L. Olson - curt@flightgear.org
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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//
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// $Id$
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#ifndef _MORSE_HXX
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#define _MORSE_HXX
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <simgear/compiler.h>
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#include <plib/sl.h>
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#include <plib/sm.h>
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// Quoting from http://www.kluft.com/~ikluft/ham/morse-intro.html by
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// Ian Kluft KO6YQ <ikluft@kluft.com>
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//
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// [begin quote]
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//
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// What is the Standard for Measuring Morse Code Speed?
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//
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// [This was adapted from the Ham Radio FAQ which used to be posted on UseNet.]
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//
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// The word PARIS was chosen as the standard length for CW code
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// speed. Each dit counts for one count, each dah counts for three
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// counts, intra-character spacing is one count, inter-character
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// spacing is three counts and inter-word spacing is seven counts, so
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// the word PARIS is exactly 50 counts:
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//
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// PPPPPPPPPPPPPP AAAAAA RRRRRRRRRR IIIIII SSSSSSSSSS
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// di da da di di da di da di di di di di di
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// 1 1 3 1 3 1 1 3 1 1 3 3 1 1 3 1 1 3 1 1 1 3 1 1 1 1 1 7 = 50
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// ^ ^ ^
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// ^Intra-character ^Inter-character Inter-word^
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//
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// So 5 words-per-minute = 250 counts-per-minute / 50 counts-per-word
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// or one count every 240 milliseconds. 13 words-per-minute is one
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// count every ~92.3 milliseconds. This method of sending code is
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// sometimes called "Slow Code", because at 5 wpm it sounds VERY SLOW.
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//
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// The "Farnsworth" method is accomplished by sending the dits and
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// dahs and intra-character spacing at a higher speed, then increasing
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// the inter-character and inter-word spacing to slow the sending
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// speed down to the desired speed. For example, to send at 5 wpm with
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// 13 wpm characters in Farnsworth method, the dits and
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// intra-character spacing would be 92.3 milliseconds, the dah would
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// be 276.9 milliseconds, the inter-character spacing would be 1.443
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// seconds and inter-word spacing would be 3.367 seconds.
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//
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// [end quote]
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// Ok, back to Curt
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// My formulation is based dit = 1 count, dah = 3 counts, 1 count for
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// intRA-character space, 3 counts for intER-character space. Target
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// is 5 wpm which by the above means 1 count = 240 milliseconds.
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//
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// AIM 1-1-7 (f) states that the frequency of the tone should be 1020
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// Hz for the VOR ident.
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static const char DI = '1';
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static const char DIT = '1';
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static const char DA = '2';
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static const char DAH = '2';
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static const char end = '0';
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static const int BYTES_PER_SECOND = 8000;
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static const int BEAT_LENGTH = 240; // milleseconds (5 wpm)
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static const int TRANSITION_BYTES = 40;
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static const int COUNT_SIZE = BYTES_PER_SECOND * BEAT_LENGTH / 1000;
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static const int DIT_SIZE = 2 * COUNT_SIZE; // 2 counts
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static const int DAH_SIZE = 4 * COUNT_SIZE; // 4 counts
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static const int SPACE_SIZE = 3 * COUNT_SIZE; // 3 counts
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static const int FREQUENCY = 1020; // AIM 1-1-7 (f) specified in Hz
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static char alphabet[26][4] = {
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{ DI, DAH, end, end }, /* A */
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{ DA, DI, DI, DIT }, /* B */
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{ DA, DI, DA, DIT }, /* C */
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{ DA, DI, DIT, end }, /* D */
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{ DIT, end, end, end }, /* E */
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{ DI, DI, DA, DIT }, /* F */
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{ DA, DA, DIT, end }, /* G */
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{ DI, DI, DI, DIT }, /* H */
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{ DI, DIT, end, end }, /* I */
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{ DI, DA, DA, DAH }, /* J */
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{ DA, DI, DAH, end }, /* K */
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{ DI, DA, DI, DIT }, /* L */
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{ DA, DAH, end, end }, /* M */
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{ DA, DIT, end, end }, /* N */
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{ DA, DA, DAH, end }, /* O */
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{ DI, DA, DA, DIT }, /* P */
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{ DA, DA, DI, DAH }, /* Q */
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{ DI, DA, DIT, end }, /* R */
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{ DI, DI, DIT, end }, /* S */
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{ DAH, end, end, end }, /* T */
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{ DI, DI, DAH, end }, /* U */
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{ DI, DI, DI, DAH }, /* V */
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{ DI, DA, DAH, end }, /* W */
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{ DA, DI, DI, DAH }, /* X */
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{ DA, DI, DA, DAH }, /* Y */
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{ DA, DA, DI, DIT } /* Z */
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};
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// manages everything we need to know for an individual sound sample
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class FGMorse {
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unsigned char dit[ DIT_SIZE ] ;
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unsigned char dah[ DAH_SIZE ] ;
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unsigned char space[ SPACE_SIZE ] ;
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public:
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FGMorse();
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~FGMorse();
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// allocate and initialize sound samples
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bool init();
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};
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#endif // _MORSE_HXX
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