quantum/audio/audio.c

   1 /* Copyright 2016 Jack Humbert
   2  *
   3  * This program is free software: you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation, either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15  */
  16 #include <stdio.h>
  17 #include <string.h>
  18 //#include <math.h>
  19 #include <avr/pgmspace.h>
  20 #include <avr/interrupt.h>
  21 #include <avr/io.h>
  22 #include "print.h"
  23 #include "audio.h"
  24 #include "keymap.h"
  25
  26 #include "eeconfig.h"
  27
  28 #define CPU_PRESCALER 8
  29
  30 // -----------------------------------------------------------------------------
  31 // Timer Abstractions
  32 // -----------------------------------------------------------------------------
  33
  34 // TIMSK3 - Timer/Counter #3 Interrupt Mask Register
  35 // Turn on/off 3A interputs, stopping/enabling the ISR calls
  36 #ifdef C6_AUDIO
  37     #define ENABLE_AUDIO_COUNTER_3_ISR TIMSK3 |= _BV(OCIE3A)
  38     #define DISABLE_AUDIO_COUNTER_3_ISR TIMSK3 &= ~_BV(OCIE3A)
  39 #endif
  40
  41 #ifdef B5_AUDIO
  42     #define ENABLE_AUDIO_COUNTER_1_ISR TIMSK1 |= _BV(OCIE1A)
  43     #define DISABLE_AUDIO_COUNTER_1_ISR TIMSK1 &= ~_BV(OCIE1A)
  44 #endif
  45
  46 // TCCR3A: Timer/Counter #3 Control Register
  47 // Compare Output Mode (COM3An) = 0b00 = Normal port operation, OC3A disconnected from PC6
  48
  49 #ifdef C6_AUDIO
  50     #define ENABLE_AUDIO_COUNTER_3_OUTPUT TCCR3A |= _BV(COM3A1);
  51     #define DISABLE_AUDIO_COUNTER_3_OUTPUT TCCR3A &= ~(_BV(COM3A1) | _BV(COM3A0));
  52 #endif
  53
  54 #ifdef B5_AUDIO
  55     #define ENABLE_AUDIO_COUNTER_1_OUTPUT TCCR1A |= _BV(COM1A1);
  56     #define DISABLE_AUDIO_COUNTER_1_OUTPUT TCCR1A &= ~(_BV(COM1A1) | _BV(COM1A0));
  57 #endif
  58
  59 // Fast PWM Mode Controls
  60
  61 #ifdef C6_AUDIO
  62     #define TIMER_3_PERIOD     ICR3
  63     #define TIMER_3_DUTY_CYCLE OCR3A
  64 #endif
  65
  66 #ifdef B5_AUDIO
  67     #define TIMER_1_PERIOD     ICR1
  68     #define TIMER_1_DUTY_CYCLE OCR1A
  69 #endif
  70
  71
  72 // -----------------------------------------------------------------------------
  73
  74
  75 int voices = 0;
  76 int voice_place = 0;
  77 float frequency = 0;
  78 int volume = 0;
  79 long position = 0;
  80
  81 float frequencies[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  82 int volumes[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  83 bool sliding = false;
  84
  85 float place = 0;
  86
  87 uint8_t * sample;
  88 uint16_t sample_length = 0;
  89
  90 bool     playing_notes = false;
  91 bool     playing_note = false;
  92 float    note_frequency = 0;
  93 float    note_length = 0;
  94 uint8_t  note_tempo = TEMPO_DEFAULT;
  95 float    note_timbre = TIMBRE_DEFAULT;
  96 uint16_t note_position = 0;
  97 float (* notes_pointer)[][2];
  98 uint16_t notes_count;
  99 bool     notes_repeat;
 100 float    notes_rest;
 101 bool     note_resting = false;
 102
 103 uint8_t current_note = 0;
 104 uint8_t rest_counter = 0;
 105
 106 #ifdef VIBRATO_ENABLE
 107 float vibrato_counter = 0;
 108 float vibrato_strength = .5;
 109 float vibrato_rate = 0.125;
 110 #endif
 111
 112 float polyphony_rate = 0;
 113
 114 static bool audio_initialized = false;
 115
 116 audio_config_t audio_config;
 117
 118 uint16_t envelope_index = 0;
 119 bool glissando = true;
 120
 121 void audio_init()
 122 {
 123
 124     // Check EEPROM
 125     if (!eeconfig_is_enabled())
 126     {
 127         eeconfig_init();
 128     }
 129     audio_config.raw = eeconfig_read_audio();
 130
 131     // Set port PC6 (OC3A and /OC4A) as output
 132
 133     #ifdef C6_AUDIO
 134         DDRC |= _BV(PORTC6);
 135     #else
 136         DDRC |= _BV(PORTC6);
 137         PORTC &= ~_BV(PORTC6);
 138     #endif
 139
 140     #ifdef B5_AUDIO
 141         DDRB |= _BV(PORTB5);
 142     #else
 143         DDRB |= _BV(PORTB5);
 144         PORTB &= ~_BV(PORTB5);
 145     #endif
 146
 147     #ifdef C6_AUDIO
 148         DISABLE_AUDIO_COUNTER_3_ISR;
 149     #endif
 150
 151     #ifdef B5_AUDIO
 152         DISABLE_AUDIO_COUNTER_1_ISR;
 153     #endif
 154
 155     // TCCR3A / TCCR3B: Timer/Counter #3 Control Registers
 156     // Compare Output Mode (COM3An) = 0b00 = Normal port operation, OC3A disconnected from PC6
 157     // Waveform Generation Mode (WGM3n) = 0b1110 = Fast PWM Mode 14 (Period = ICR3, Duty Cycle = OCR3A)
 158     // Clock Select (CS3n) = 0b010 = Clock / 8
 159
 160     #ifdef C6_AUDIO
 161         TCCR3A = (0 << COM3A1) | (0 << COM3A0) | (1 << WGM31) | (0 << WGM30);
 162         TCCR3B = (1 << WGM33)  | (1 << WGM32)  | (0 << CS32)  | (1 << CS31) | (0 << CS30);
 163     #endif
 164
 165     #ifdef B5_AUDIO
 166         TCCR1A = (0 << COM1A1) | (0 << COM1A0) | (1 << WGM11) | (0 << WGM10);
 167         TCCR1B = (1 << WGM13)  | (1 << WGM12)  | (0 << CS12)  | (1 << CS11) | (0 << CS10);
 168     #endif
 169
 170     audio_initialized = true;
 171 }
 172
 173 void stop_all_notes()
 174 {
 175     dprintf("audio stop all notes");
 176
 177     if (!audio_initialized) {
 178         audio_init();
 179     }
 180     voices = 0;
 181
 182
 183     #ifdef C6_AUDIO
 184         DISABLE_AUDIO_COUNTER_3_ISR;
 185         DISABLE_AUDIO_COUNTER_3_OUTPUT;
 186     #endif
 187
 188     #ifdef B5_AUDIO
 189         DISABLE_AUDIO_COUNTER_1_ISR;
 190         DISABLE_AUDIO_COUNTER_1_OUTPUT;
 191     #endif
 192
 193     playing_notes = false;
 194     playing_note = false;
 195     frequency = 0;
 196     volume = 0;
 197
 198     for (uint8_t i = 0; i < 8; i++)
 199     {
 200         frequencies[i] = 0;
 201         volumes[i] = 0;
 202     }
 203 }
 204
 205 void stop_note(float freq)
 206 {
 207     dprintf("audio stop note freq=%d", (int)freq);
 208
 209     if (playing_note) {
 210         if (!audio_initialized) {
 211             audio_init();
 212         }
 213         for (int i = 7; i >= 0; i--) {
 214             if (frequencies[i] == freq) {
 215                 frequencies[i] = 0;
 216                 volumes[i] = 0;
 217                 for (int j = i; (j < 7); j++) {
 218                     frequencies[j] = frequencies[j+1];
 219                     frequencies[j+1] = 0;
 220                     volumes[j] = volumes[j+1];
 221                     volumes[j+1] = 0;
 222                 }
 223                 break;
 224             }
 225         }
 226         voices--;
 227         if (voices < 0)
 228             voices = 0;
 229         if (voice_place >= voices) {
 230             voice_place = 0;
 231         }
 232         if (voices == 0) {
 233             #ifdef C6_AUDIO
 234                 DISABLE_AUDIO_COUNTER_3_ISR;
 235                 DISABLE_AUDIO_COUNTER_3_OUTPUT;
 236             #endif
 237             #ifdef B5_AUDIO
 238                 DISABLE_AUDIO_COUNTER_1_ISR;
 239                 DISABLE_AUDIO_COUNTER_1_OUTPUT;
 240             #endif
 241             frequency = 0;
 242             volume = 0;
 243             playing_note = false;
 244         }
 245     }
 246 }
 247
 248 #ifdef VIBRATO_ENABLE
 249
 250 float mod(float a, int b)
 251 {
 252     float r = fmod(a, b);
 253     return r < 0 ? r + b : r;
 254 }
 255
 256 float vibrato(float average_freq) {
 257     #ifdef VIBRATO_STRENGTH_ENABLE
 258         float vibrated_freq = average_freq * pow(vibrato_lut[(int)vibrato_counter], vibrato_strength);
 259     #else
 260         float vibrated_freq = average_freq * vibrato_lut[(int)vibrato_counter];
 261     #endif
 262     vibrato_counter = mod((vibrato_counter + vibrato_rate * (1.0 + 440.0/average_freq)), VIBRATO_LUT_LENGTH);
 263     return vibrated_freq;
 264 }
 265
 266 #endif
 267
 268 #ifdef C6_AUDIO
 269 ISR(TIMER3_COMPA_vect)
 270 {
 271     float freq;
 272
 273     if (playing_note) {
 274         if (voices > 0) {
 275             if (polyphony_rate > 0) {
 276                 if (voices > 1) {
 277                     voice_place %= voices;
 278                     if (place++ > (frequencies[voice_place] / polyphony_rate / CPU_PRESCALER)) {
 279                         voice_place = (voice_place + 1) % voices;
 280                         place = 0.0;
 281                     }
 282                 }
 283
 284                 #ifdef VIBRATO_ENABLE
 285                     if (vibrato_strength > 0) {
 286                         freq = vibrato(frequencies[voice_place]);
 287                     } else {
 288                         freq = frequencies[voice_place];
 289                     }
 290                 #else
 291                     freq = frequencies[voice_place];
 292                 #endif
 293             } else {
 294                 if (glissando) {
 295                     if (frequency != 0 && frequency < frequencies[voices - 1] && frequency < frequencies[voices - 1] * pow(2, -440/frequencies[voices - 1]/12/2)) {
 296                         frequency = frequency * pow(2, 440/frequency/12/2);
 297                     } else if (frequency != 0 && frequency > frequencies[voices - 1] && frequency > frequencies[voices - 1] * pow(2, 440/frequencies[voices - 1]/12/2)) {
 298                         frequency = frequency * pow(2, -440/frequency/12/2);
 299                     } else {
 300                         frequency = frequencies[voices - 1];
 301                     }
 302                 } else {
 303                     frequency = frequencies[voices - 1];
 304                 }
 305
 306                 #ifdef VIBRATO_ENABLE
 307                     if (vibrato_strength > 0) {
 308                         freq = vibrato(frequency);
 309                     } else {
 310                         freq = frequency;
 311                     }
 312                 #else
 313                     freq = frequency;
 314                 #endif
 315             }
 316
 317             if (envelope_index < 65535) {
 318                 envelope_index++;
 319             }
 320
 321             freq = voice_envelope(freq);
 322
 323             if (freq < 30.517578125) {
 324                 freq = 30.52;
 325             }
 326
 327             TIMER_3_PERIOD = (uint16_t)(((float)F_CPU) / (freq * CPU_PRESCALER));
 328             TIMER_3_DUTY_CYCLE = (uint16_t)((((float)F_CPU) / (freq * CPU_PRESCALER)) * note_timbre);
 329         }
 330     }
 331
 332     if (playing_notes) {
 333         if (note_frequency > 0) {
 334             #ifdef VIBRATO_ENABLE
 335                 if (vibrato_strength > 0) {
 336                     freq = vibrato(note_frequency);
 337                 } else {
 338                     freq = note_frequency;
 339                 }
 340             #else
 341                     freq = note_frequency;
 342             #endif
 343
 344             if (envelope_index < 65535) {
 345                 envelope_index++;
 346             }
 347             freq = voice_envelope(freq);
 348
 349             TIMER_3_PERIOD = (uint16_t)(((float)F_CPU) / (freq * CPU_PRESCALER));
 350             TIMER_3_DUTY_CYCLE = (uint16_t)((((float)F_CPU) / (freq * CPU_PRESCALER)) * note_timbre);
 351         } else {
 352             TIMER_3_PERIOD = 0;
 353             TIMER_3_DUTY_CYCLE = 0;
 354         }
 355
 356         note_position++;
 357         bool end_of_note = false;
 358         if (TIMER_3_PERIOD > 0) {
 359             end_of_note = (note_position >= (note_length / TIMER_3_PERIOD * 0xFFFF));
 360         } else {
 361             end_of_note = (note_position >= (note_length * 0x7FF));
 362         }
 363
 364         if (end_of_note) {
 365             current_note++;
 366             if (current_note >= notes_count) {
 367                 if (notes_repeat) {
 368                     current_note = 0;
 369                 } else {
 370                     DISABLE_AUDIO_COUNTER_3_ISR;
 371                     DISABLE_AUDIO_COUNTER_3_OUTPUT;
 372                     playing_notes = false;
 373                     return;
 374                 }
 375             }
 376             if (!note_resting && (notes_rest > 0)) {
 377                 note_resting = true;
 378                 note_frequency = 0;
 379                 note_length = notes_rest;
 380                 current_note--;
 381             } else {
 382                 note_resting = false;
 383                 envelope_index = 0;
 384                 note_frequency = (*notes_pointer)[current_note][0];
 385                 note_length = ((*notes_pointer)[current_note][1] / 4) * (((float)note_tempo) / 100);
 386             }
 387
 388             note_position = 0;
 389         }
 390     }
 391
 392     if (!audio_config.enable) {
 393         playing_notes = false;
 394         playing_note = false;
 395     }
 396 }
 397 #endif
 398
 399 #ifdef B5_AUDIO
 400 ISR(TIMER1_COMPA_vect)
 401 {
 402     float freq;
 403
 404     if (playing_note) {
 405         if (voices > 0) {
 406             if (polyphony_rate > 0) {
 407                 if (voices > 1) {
 408                     voice_place %= voices;
 409                     if (place++ > (frequencies[voice_place] / polyphony_rate / CPU_PRESCALER)) {
 410                         voice_place = (voice_place + 1) % voices;
 411                         place = 0.0;
 412                     }
 413                 }
 414
 415                 #ifdef VIBRATO_ENABLE
 416                     if (vibrato_strength > 0) {
 417                         freq = vibrato(frequencies[voice_place]);
 418                     } else {
 419                         freq = frequencies[voice_place];
 420                     }
 421                 #else
 422                     freq = frequencies[voice_place];
 423                 #endif
 424             } else {
 425                 if (glissando) {
 426                     if (frequency != 0 && frequency < frequencies[voices - 1] && frequency < frequencies[voices - 1] * pow(2, -440/frequencies[voices - 1]/12/2)) {
 427                         frequency = frequency * pow(2, 440/frequency/12/2);
 428                     } else if (frequency != 0 && frequency > frequencies[voices - 1] && frequency > frequencies[voices - 1] * pow(2, 440/frequencies[voices - 1]/12/2)) {
 429                         frequency = frequency * pow(2, -440/frequency/12/2);
 430                     } else {
 431                         frequency = frequencies[voices - 1];
 432                     }
 433                 } else {
 434                     frequency = frequencies[voices - 1];
 435                 }
 436
 437                 #ifdef VIBRATO_ENABLE
 438                     if (vibrato_strength > 0) {
 439                         freq = vibrato(frequency);
 440                     } else {
 441                         freq = frequency;
 442                     }
 443                 #else
 444                     freq = frequency;
 445                 #endif
 446             }
 447
 448             if (envelope_index < 65535) {
 449                 envelope_index++;
 450             }
 451
 452             freq = voice_envelope(freq);
 453
 454             if (freq < 30.517578125) {
 455                 freq = 30.52;
 456             }
 457
 458             TIMER_1_PERIOD = (uint16_t)(((float)F_CPU) / (freq * CPU_PRESCALER));
 459             TIMER_1_DUTY_CYCLE = (uint16_t)((((float)F_CPU) / (freq * CPU_PRESCALER)) * note_timbre);
 460         }
 461     }
 462
 463     if (playing_notes) {
 464         if (note_frequency > 0) {
 465             #ifdef VIBRATO_ENABLE
 466                 if (vibrato_strength > 0) {
 467                     freq = vibrato(note_frequency);
 468                 } else {
 469                     freq = note_frequency;
 470                 }
 471             #else
 472                     freq = note_frequency;
 473             #endif
 474
 475             if (envelope_index < 65535) {
 476                 envelope_index++;
 477             }
 478             freq = voice_envelope(freq);
 479
 480             TIMER_1_PERIOD = (uint16_t)(((float)F_CPU) / (freq * CPU_PRESCALER));
 481             TIMER_1_DUTY_CYCLE = (uint16_t)((((float)F_CPU) / (freq * CPU_PRESCALER)) * note_timbre);
 482         } else {
 483             TIMER_1_PERIOD = 0;
 484             TIMER_1_DUTY_CYCLE = 0;
 485         }
 486
 487         note_position++;
 488         bool end_of_note = false;
 489         if (TIMER_1_PERIOD > 0) {
 490             end_of_note = (note_position >= (note_length / TIMER_1_PERIOD * 0xFFFF));
 491         } else {
 492             end_of_note = (note_position >= (note_length * 0x7FF));
 493         }
 494
 495         if (end_of_note) {
 496             current_note++;
 497             if (current_note >= notes_count) {
 498                 if (notes_repeat) {
 499                     current_note = 0;
 500                 } else {
 501                     DISABLE_AUDIO_COUNTER_1_ISR;
 502                     DISABLE_AUDIO_COUNTER_1_OUTPUT;
 503                     playing_notes = false;
 504                     return;
 505                 }
 506             }
 507             if (!note_resting && (notes_rest > 0)) {
 508                 note_resting = true;
 509                 note_frequency = 0;
 510                 note_length = notes_rest;
 511                 current_note--;
 512             } else {
 513                 note_resting = false;
 514                 envelope_index = 0;
 515                 note_frequency = (*notes_pointer)[current_note][0];
 516                 note_length = ((*notes_pointer)[current_note][1] / 4) * (((float)note_tempo) / 100);
 517             }
 518
 519             note_position = 0;
 520         }
 521     }
 522
 523     if (!audio_config.enable) {
 524         playing_notes = false;
 525         playing_note = false;
 526     }
 527 }
 528 #endif
 529
 530 void play_note(float freq, int vol) {
 531
 532     dprintf("audio play note freq=%d vol=%d", (int)freq, vol);
 533
 534     if (!audio_initialized) {
 535         audio_init();
 536     }
 537
 538     if (audio_config.enable && voices < 8) {
 539         #ifdef C6_AUDIO
 540             DISABLE_AUDIO_COUNTER_3_ISR;
 541         #endif
 542         #ifdef B5_AUDIO
 543             DISABLE_AUDIO_COUNTER_1_ISR;
 544         #endif
 545
 546         // Cancel notes if notes are playing
 547         if (playing_notes)
 548             stop_all_notes();
 549
 550         playing_note = true;
 551
 552         envelope_index = 0;
 553
 554         if (freq > 0) {
 555             frequencies[voices] = freq;
 556             volumes[voices] = vol;
 557             voices++;
 558         }
 559
 560         #ifdef C6_AUDIO
 561             ENABLE_AUDIO_COUNTER_3_ISR;
 562             ENABLE_AUDIO_COUNTER_3_OUTPUT;
 563         #endif
 564         #ifdef B5_AUDIO
 565             ENABLE_AUDIO_COUNTER_1_ISR;
 566             ENABLE_AUDIO_COUNTER_1_OUTPUT;
 567         #endif
 568     }
 569
 570 }
 571
 572 void play_notes(float (*np)[][2], uint16_t n_count, bool n_repeat, float n_rest)
 573 {
 574
 575     if (!audio_initialized) {
 576         audio_init();
 577     }
 578
 579     if (audio_config.enable) {
 580
 581         #ifdef C6_AUDIO
 582             DISABLE_AUDIO_COUNTER_3_ISR;
 583         #endif
 584         #ifdef B5_AUDIO
 585             DISABLE_AUDIO_COUNTER_1_ISR;
 586         #endif
 587
 588         // Cancel note if a note is playing
 589         if (playing_note)
 590             stop_all_notes();
 591
 592         playing_notes = true;
 593
 594         notes_pointer = np;
 595         notes_count = n_count;
 596         notes_repeat = n_repeat;
 597         notes_rest = n_rest;
 598
 599         place = 0;
 600         current_note = 0;
 601
 602         note_frequency = (*notes_pointer)[current_note][0];
 603         note_length = ((*notes_pointer)[current_note][1] / 4) * (((float)note_tempo) / 100);
 604         note_position = 0;
 605
 606
 607         #ifdef C6_AUDIO
 608             ENABLE_AUDIO_COUNTER_3_ISR;
 609             ENABLE_AUDIO_COUNTER_3_OUTPUT;
 610         #endif
 611         #ifdef B5_AUDIO
 612             ENABLE_AUDIO_COUNTER_1_ISR;
 613             ENABLE_AUDIO_COUNTER_1_OUTPUT;
 614         #endif
 615     }
 616
 617 }
 618
 619 bool is_playing_notes(void) {
 620     return playing_notes;
 621 }
 622
 623 bool is_audio_on(void) {
 624     return (audio_config.enable != 0);
 625 }
 626
 627 void audio_toggle(void) {
 628     audio_config.enable ^= 1;
 629     eeconfig_update_audio(audio_config.raw);
 630     if (audio_config.enable)
 631         audio_on_user();
 632 }
 633
 634 void audio_on(void) {
 635     audio_config.enable = 1;
 636     eeconfig_update_audio(audio_config.raw);
 637     audio_on_user();
 638 }
 639
 640 void audio_off(void) {
 641     audio_config.enable = 0;
 642     eeconfig_update_audio(audio_config.raw);
 643 }
 644
 645 #ifdef VIBRATO_ENABLE
 646
 647 // Vibrato rate functions
 648
 649 void set_vibrato_rate(float rate) {
 650     vibrato_rate = rate;
 651 }
 652
 653 void increase_vibrato_rate(float change) {
 654     vibrato_rate *= change;
 655 }
 656
 657 void decrease_vibrato_rate(float change) {
 658     vibrato_rate /= change;
 659 }
 660
 661 #ifdef VIBRATO_STRENGTH_ENABLE
 662
 663 void set_vibrato_strength(float strength) {
 664     vibrato_strength = strength;
 665 }
 666
 667 void increase_vibrato_strength(float change) {
 668     vibrato_strength *= change;
 669 }
 670
 671 void decrease_vibrato_strength(float change) {
 672     vibrato_strength /= change;
 673 }
 674
 675 #endif  /* VIBRATO_STRENGTH_ENABLE */
 676
 677 #endif /* VIBRATO_ENABLE */
 678
 679 // Polyphony functions
 680
 681 void set_polyphony_rate(float rate) {
 682     polyphony_rate = rate;
 683 }
 684
 685 void enable_polyphony() {
 686     polyphony_rate = 5;
 687 }
 688
 689 void disable_polyphony() {
 690     polyphony_rate = 0;
 691 }
 692
 693 void increase_polyphony_rate(float change) {
 694     polyphony_rate *= change;
 695 }
 696
 697 void decrease_polyphony_rate(float change) {
 698     polyphony_rate /= change;
 699 }
 700
 701 // Timbre function
 702
 703 void set_timbre(float timbre) {
 704     note_timbre = timbre;
 705 }
 706
 707 // Tempo functions
 708
 709 void set_tempo(uint8_t tempo) {
 710     note_tempo = tempo;
 711 }
 712
 713 void decrease_tempo(uint8_t tempo_change) {
 714     note_tempo += tempo_change;
 715 }
 716
 717 void increase_tempo(uint8_t tempo_change) {
 718     if (note_tempo - tempo_change < 10) {
 719         note_tempo = 10;
 720     } else {
 721         note_tempo -= tempo_change;
 722     }
 723 }