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414 lines
11 KiB
414 lines
11 KiB
/** @file mmelody.c
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@author M. P. Hayes, UCECE
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@date 20 April 2007
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@brief Play simple melodies.
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*/
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#include "system.h"
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#include "mmelody.h"
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/* By default notes are in the scale C4 -> C5.
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Note the first 12 frets on a six string guitar covers 3 octaves
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from the pitch E2 (82.41 Hz) to the pitch E5 (659.26 Hz).
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Tunes are specified using the notation C4C5F4G4C4 but for brevity
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this can be simplified to C4C5F4GC where the previously specified
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octave number persists. A problem with this notation is the
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verbosity when we have something like B2C3B2C3. Most melodies will
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only require 2 and 3 at the most octaves. The ABC music notation
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uses CDEFGABcdefgabc'd'e'f'g'a'b'c' to denote 3 octaves from C2 to
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C5? This uses numbers to indicate note duration, for example, C2
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denotes a C of twice the standard duration.
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By default notes are crotchets (quarter notes) and tempos are
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defined in beats per minute. If we assume 4/4 time, then each beat
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has a quarter-note duration.
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The note duration can be halved with a comma suffix, e.g., A,
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The note duration can be extended by a half with a dot suffix, e.g., A.
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The note duration can be doubled with a slash suffix, e.g., A/
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The note duration can be trebled with two slash suffixes, e.g., A//
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(this can be continued to lengthen the note).
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If there are lots of quavers (eighth notes), then the default note
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duration can be switched using *8. *4 returns to quarter note timing.
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Rests are specified with a space character. The timing modifiers ,
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. and / can be used.
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<ABC> is equivalent to ABCABC
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<ABC>3 is equivalent to ABCABCABC
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ABC: performs an infinite repeat of ABC
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<ABC]1DE]2FG> represents ABCDEABCFG where ]n denotes alternate
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endings.
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A+ sounds an octave higher
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A- sounds an octave lower
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@120 sets the tempo to 120 beats per minute
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This could be made a lot more flexible but the orginal
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implementation had a tight memory constraint. Possible extensions:
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* For emphasis perhaps use ^ to indicate louder, for example, C^.
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Similarly, to make a note quieter it could have a v suffix.
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* Use | for bar markers; these can be ignored.
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* Time signatures.
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* Nested loops, e.g., <AB<ABC>>
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* sixteenth notes? Perhaps A,,
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* Perhaps lower case for eighth notes?
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* Triplets and other irrational tuplets? A triplet quarter note
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has 2 / 3 the duration of a quarter note while a triplet eighth note
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has 2 / 3 the duration of of an eighth note. This can be achieved
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using *6 or *12.
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*/
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enum {MMELODY_SCALE_SIZE = 12};
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/* Assume each beat is a quarter note. */
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enum {MMELODY_BEAT_FRACTION = 4};
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/* Scale factor for fraction of a symbol timing. */
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enum {MMELODY_DURATION_FRACTION = 4};
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/* How long to release note before sounding the next one. */
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#define MMELODY_RELEASE_MS 50
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static void
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mmelody_ticker_set (mmelody_t mmelody)
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{
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/* The duration of a beat varies with the time signature:
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2/2 : minum (half note)
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4/4 : crotchet (quarter note)
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6/8, 9/8, 12/8 : dotted crotchet (one and a half quarter notes)
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Currently, there is no time signature support so we assume 4/4.
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This means a beat is a quarter note and a bar is four quarter
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notes.
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ticks_per_beat = poll_rate * 60 / speed
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symbols_per_beat = symbol_fraction / MMELODY_BEAT_FRACTION
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ticks_per_symbol = ticks_per_beat / symbols_per_beat
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ticks_per_unit = ticks_per_symbol / MMELODY_DURATION_FRACTION
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ticks_per_note = ticks_per_beat * MMELODY_BEAT_FRACTION
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= ticks_per_unit * symbol_fraction
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* MMELODY_DURATION_FRACTION
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The duration is specified as the actual duration scaled by
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MMELODY_DURATION_FRACTION so that it can specify half periods.
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With symbol_fraction = 4, speed = 50, and poll_rate of 200 this
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gives a result of 60. */
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mmelody->unit_ticks
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= (mmelody->poll_rate * 60 * MMELODY_BEAT_FRACTION)
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/ (mmelody->speed * mmelody->symbol_fraction
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* MMELODY_DURATION_FRACTION);
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}
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static void
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mmelody_note_on (mmelody_t mmelody, mmelody_note_t note, uint8_t duration)
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{
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/* The duration is in terms of the half the duration of a symbol. */
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mmelody->play_callback (mmelody->play_callback_data, note,
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mmelody->volume);
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mmelody->note = note;
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/* Determine ticks between sounding notes (this needs to be a
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minimum of 1). If we assume a release period of 50 ms,
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this will give a count of 10 ticks at 200 Hz sampling. */
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mmelody->ticks2 = mmelody->release_ticks;
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/* Determine ticks before turning the note off. */
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mmelody->ticks1 = mmelody->unit_ticks * duration - mmelody->ticks2;
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}
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static void
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mmelody_note_off (mmelody_t mmelody)
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{
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mmelody->play_callback (mmelody->play_callback_data,
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mmelody->note, 0);
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mmelody->note = 0;
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}
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/* Specify the default note length in fractions of a measure (bar).
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A value of 4 is the default which makes each note a quarter note. */
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static void
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mmelody_symbol_fraction_set (mmelody_t mmelody, uint8_t symbol_fraction)
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{
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mmelody->symbol_fraction = symbol_fraction;
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mmelody_ticker_set (mmelody);
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}
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static mmelody_note_t
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mmelody_char_to_note (uint8_t ch)
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{
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/* A = 9, B = 11, C = 0, D = 2, E = 4, F = 5, G = 7 */
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static const mmelody_note_t const lookup[] = {9, 11, 0, 2, 4, 5, 7};
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return lookup[ch - 'A'];
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}
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/* Scan next part of melody until a note or end of melody is found. */
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static const char *
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mmelody_scan (mmelody_t mmelody, const char *str)
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{
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while (1)
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{
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uint8_t num;
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char cmd;
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char modifier;
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bool have_hash;
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bool have_num;
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mmelody_note_t note = 0;
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uint8_t duration = 1;
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/* Play rest at end of melody. */
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if (! *str)
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{
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mmelody_note_off (mmelody);
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return str;
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}
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cmd = *str++;
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have_hash = *str == '#';
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if (have_hash)
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str++;
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modifier = 0;
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if (*str == '+' || *str == '-')
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modifier = *str++;
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have_num = 0;
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num = 0;
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while (*str >= '0' && *str <= '9')
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{
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have_num = 1;
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num = num * 10 + *str++ - '0';
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}
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switch (cmd)
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{
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/* Repeat sequence from start. */
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case ':':
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str = mmelody->start;
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continue;
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/* Define start of loop. */
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case '<':
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/* We could implement a small stack to allow nested
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loops. */
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mmelody->loop_start = str;
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mmelody->loop_count = 0;
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continue;
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/* Loop. */
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case '>':
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mmelody->loop_count++;
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if (!num)
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num = 2;
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if (mmelody->loop_count < num)
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{
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/* Jump to start of loop. If no start of loop symbol,
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jump to start. */
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str = mmelody->loop_start;
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if (!str)
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str = mmelody->start;
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}
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continue;
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/* Alternate endings. */
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case '[':
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if (mmelody->loop_count == num - 1)
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continue;
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/* Skip to next alternate ending, the end of loop, or end of
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melody. */
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while (*str && *str != '[' && *str != '>')
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str++;
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continue;
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case '*':
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if (num)
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mmelody_symbol_fraction_set (mmelody, num);
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continue;
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case '@':
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if (num)
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mmelody_speed_set (mmelody, num);
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continue;
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case 'A':
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case 'B':
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case 'C':
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case 'D':
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case 'E':
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case 'F':
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case 'G':
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note = mmelody_char_to_note (cmd);
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if (have_hash)
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note++;
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if (have_num)
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mmelody->octave = num;
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if (modifier == '+')
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note += MMELODY_SCALE_SIZE;
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if (modifier == '-')
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note -= MMELODY_SCALE_SIZE;
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/* Convert note to MIDI note number. */
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note += (mmelody->octave + 1) * MMELODY_SCALE_SIZE;
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/* Fall through. */
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case ' ':
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while (*str == '/')
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{
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duration++;
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str++;
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}
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duration = duration * MMELODY_DURATION_FRACTION;
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if (*str == '.')
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{
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/* Dotted quarter note. */
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duration += duration / 2;
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str++;
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}
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else if (*str == ',')
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{
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/* Eighth note. */
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str++;
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duration = duration / 2;
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}
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mmelody_note_on (mmelody, note, duration);
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return str;
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break;
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default:
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return str;
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break;
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}
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}
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return str;
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}
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void
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mmelody_play (mmelody_t mmelody, const char *str)
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{
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mmelody->cur = mmelody->start = str;
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mmelody->loop_start = 0;
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mmelody->loop_count = 0;
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mmelody->octave = MMELODY_OCTAVE_DEFAULT;
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/* Default to quarter notes. */
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mmelody_symbol_fraction_set (mmelody, 4);
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/* Stop what is currently sounding. */
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mmelody_note_off (mmelody);
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mmelody->ticks1 = 0;
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mmelody->ticks2 = 1;
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}
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/* Set (base) speed in beats per minute (BPM). */
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void
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mmelody_speed_set (mmelody_t mmelody, mmelody_speed_t speed)
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{
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/* With 8 bits for the tempo (in bpm), the max tempo is 255 bpm.
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This corresponds to 4.25 beats per second. If the minimum time
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to release a note is 1 / 8 of a quarter note, then we need to
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poll at a rate of at least 4.25 * 8 = 34 times per second. */
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mmelody->speed = speed;
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mmelody_ticker_set (mmelody);
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}
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/* Set volume as percentage of maximum. */
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void
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mmelody_volume_set (mmelody_t mmelody, mmelody_volume_t volume)
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{
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mmelody->volume = volume;
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}
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bool
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mmelody_active_p (mmelody_t mmelody)
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{
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return mmelody->cur != 0;
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}
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void
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mmelody_update (mmelody_t mmelody)
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{
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if (!mmelody->cur)
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return;
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if (mmelody->ticks1)
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{
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mmelody->ticks1--;
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if (!mmelody->ticks1)
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mmelody_note_off (mmelody);
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}
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else
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{
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if (mmelody->ticks2)
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{
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mmelody->ticks2--;
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if (!mmelody->ticks2)
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mmelody->cur = mmelody_scan (mmelody, mmelody->cur);
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}
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}
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}
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mmelody_t
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mmelody_init (mmelody_obj_t *mmelody,
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uint16_t poll_rate,
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mmelody_callback_t play_callback,
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void *play_callback_data)
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{
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mmelody->poll_rate = poll_rate;
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mmelody->play_callback = play_callback;
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mmelody->play_callback_data = play_callback_data;
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mmelody->volume = 100;
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mmelody->note = 0;
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mmelody->ticks1 = 0;
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mmelody->ticks2 = 0;
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mmelody->release_ticks = (poll_rate * MMELODY_RELEASE_MS) / 1000;
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mmelody->symbol_fraction = 4;
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mmelody->speed = MMELODY_SPEED_DEFAULT;
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return mmelody;
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}
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