/*

*

* Arduino Synth

* Copyright 2012-2013 Jon Ronen-Drori

*

*

* A simple Arduino-based one-note synthesizer

* with vibrato, low-pass filter, resonance,

* distortion, and tremolo

*

* Inspiration and pieces of code taken from:

* - Auduino (http://code.google.com/p/tinkerit/wiki/Auduino)

* - Arduino Octosynth (http://www.instructables.com/id/The-Arduino-OctoSynth/)

* - sfxr (http://www.drpetter.se/project_sfxr.html)

* - Speaker PCM (http://www.arduino.cc/playground/Code/PCMAudio)

*

*

* This program is free software: you can redistribute it and/or modify

* it under the terms of the GNU General Public License as published by

* the Free Software Foundation, either version 3 of the License, or

* (at your option) any later version.

*

* This program is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

* GNU General Public License for more details.

*

* You should have received a copy of the GNU General Public License

* along with this program. If not, see <http://www.gnu.org/licenses/>.

*

*

*/

#include <avr/io.h>

#include <avr/interrupt.h>

#include <avr/pgmspace.h>

#include "Arduino.h"

// digital inputs

#define TONE1_PIN 9

#define TONE2_PIN 10

#define TONE3_PIN 11

#define TONE4_PIN 12

#define TONE5_PIN 13

//

// Note:

// TONE5_PIN should be changed if you really want to use an Arduino Uno...

// pin #13 is usually the LED and may not work properly as an input

//

#define LOWPASS_PIN 5

#define FREQ_PIN 6

#define DIST_PIN 7

#define TREM_PIN 8

// "analog" output

#define PWM_PIN 3

#define PWM_VALUE OCR2B

// interrupt on timer comparison

#define PWM_INTERRUPT TIMER1_COMPA_vect

#define ATTACK_CTRL 0

#define RELEASE_CTRL 1

#define VIBRATO_CTRL 2

#define RESONANCE_CTRL 3

void setup();

void loop();

static void reset_sample();

// 0 for rough sawtooth, 1 for sawtooth, 2 for sine, 3 for square

static const unsigned char g_wave_type = 1;

// tone frequency

static unsigned short g_base_freq;

static unsigned short g_curr_freq;

static unsigned short g_freq_ramp_cnt;

// base frequency generation

static unsigned short g_phase;

//

// envelope

//

// type: 0=amplitude, 1=low-pass, 2=frequency

static unsigned char g_env_type;

// stage: 0=attack, 1=sustain, 2=release, 3=silence

static unsigned char g_env_stage;

static unsigned short g_env_time;

static unsigned short g_env_lengths[2];

// low-pass filter

static unsigned char g_lpf_resonance;

static unsigned char g_lpf_freq;

static short g_lpf_prev;

static short g_lpf_prev_delta;

// vibrato

static unsigned short g_vib_phase;

static unsigned char g_vib_strength;

static short g_vib_fix_accum;

// tremolo and distortion

static unsigned short g_interrupt_cnt;

// buttons

static uint8_t g_button_status;

static uint8_t g_current_pitch_bit;

static uint8_t g_dist_status;

static uint8_t g_trem_status;

static const short phase_to_delta[4] = {1,-1,-1,1};

static const unsigned char g_rand_shit[256] = {

127, 245, 223, 255, 254, 255, 255, 255, 255, 191, 254, 255, 255, 255, 255, 223,

255, 191, 254, 247, 255, 255, 255, 255, 223, 255, 61, 255, 183, 255, 255, 255,

255, 191, 249, 255, 255, 245, 255, 250, 215, 255, 255, 255, 127, 255, 255, 255,

255, 223, 255, 255, 255, 255, 255, 255, 255, 127, 255, 254, 243, 255, 239, 255,

237, 255, 255, 255, 255, 247, 255, 255, 255, 255, 187, 255, 251, 251, 255, 223,

255, 253, 255, 255, 255, 255, 127, 255, 191, 255, 255, 255, 255, 255, 223, 255,

255, 251, 123, 255, 253, 254, 239, 251, 255, 255, 223, 255, 255, 255, 255, 255,

251, 255, 251, 223, 255, 231, 251, 255, 255, 255, 221, 255, 251, 255, 255, 223,

255, 219, 255, 245, 255, 255, 255, 255, 255, 255, 251, 255, 59, 255, 255, 223,

255, 191, 255, 127, 255, 223, 255, 127, 255, 255, 255, 255, 255, 255, 255, 119,

255, 255, 255, 253, 255, 255, 253, 255, 255, 254, 252, 247, 255, 255, 255, 62,

255, 251, 247, 255, 189, 255, 255, 255, 255, 126, 251, 253, 255, 255, 191, 255,

255, 127, 222, 255, 159, 255, 255, 249, 255, 255, 191, 255, 254, 255, 255, 255,

255, 207, 221, 251, 253, 255, 255, 255, 190, 191, 255, 255, 255, 255, 127, 255,

255, 243, 255, 247, 255, 255, 253, 255, 255, 223, 255, 255, 255, 251, 255, 255,

255, 191, 255, 254, 191, 255, 255, 255, 251, 255, 255, 191, 255, 255, 255, 255

};

/* TODO: for some reason, this doesn't work properly

const prog_int16_t mysin_table[2048] = {

0, 3, 6, 9, 12, 15, 18, 21,

25, 28, 31, 34, 37, 40, 43, 47,

50, 53, 56, 59, 62, 65, 69, 72,

75, 78, 81, 84, 87, 90, 94, 97,

100, 103, 106, 109, 112, 115, 119, 122,

125, 128, 131, 134, 137, 140, 144, 147,

150, 153, 156, 159, 162, 165, 168, 171,

175, 178, 181, 184, 187, 190, 193, 196,

199, 202, 205, 209, 212, 215, 218, 221,

224, 227, 230, 233, 236, 239, 242, 245,

248, 251, 254, 257, 260, 264, 267, 270,

273, 276, 279, 282, 285, 288, 291, 294,

297, 300, 303, 306, 309, 312, 315, 318,

321, 324, 327, 330, 333, 336, 339, 342,

344, 347, 350, 353, 356, 359, 362, 365,

368, 371, 374, 377, 380, 383, 386, 388,

391, 394, 397, 400, 403, 406, 409, 412,

414, 417, 420, 423, 426, 429, 432, 434,

437, 440, 443, 446, 449, 451, 454, 457,

460, 463, 466, 468, 471, 474, 477, 479,

482, 485, 488, 491, 493, 496, 499, 501,

504, 507, 510, 512, 515, 518, 521, 523,

526, 529, 531, 534, 537, 539, 542, 545,

547, 550, 553, 555, 558, 561, 563, 566,

568, 571, 574, 576, 579, 581, 584, 587,

589, 592, 594, 597, 599, 602, 604, 607,

609, 612, 615, 617, 620, 622, 625, 627,

629, 632, 634, 637, 639, 642, 644, 647,

649, 652, 654, 656, 659, 661, 664, 666,

668, 671, 673, 675, 678, 680, 683, 685,

687, 690, 692, 694, 696, 699, 701, 703,

706, 708, 710, 712, 715, 717, 719, 721,

724, 726, 728, 730, 732, 735, 737, 739,

741, 743, 745, 748, 750, 752, 754, 756,

758, 760, 762, 765, 767, 769, 771, 773,

775, 777, 779, 781, 783, 785, 787, 789,

791, 793, 795, 797, 799, 801, 803, 805,

807, 809, 811, 813, 814, 816, 818, 820,

822, 824, 826, 828, 829, 831, 833, 835,

837, 839, 840, 842, 844, 846, 847, 849,

851, 853, 854, 856, 858, 860, 861, 863,

865, 866, 868, 870, 871, 873, 875, 876,

878, 879, 881, 883, 884, 886, 887, 889,

890, 892, 894, 895, 897, 898, 900, 901,

903, 904, 906, 907, 908, 910, 911, 913,

914, 916, 917, 918, 920, 921, 922, 924,

925, 927, 928, 929, 930, 932, 933, 934,

936, 937, 938, 939, 941, 942, 943, 944,

946, 947, 948, 949, 950, 951, 953, 954,

955, 956, 957, 958, 959, 960, 962, 963,

964, 965, 966, 967, 968, 969, 970, 971,

972, 973, 974, 975, 976, 977, 978, 978,

979, 980, 981, 982, 983, 984, 985, 986,

986, 987, 988, 989, 990, 990, 991, 992,

993, 994, 994, 995, 996, 997, 997, 998,

999, 999, 1000, 1001, 1001, 1002, 1003, 1003,

1004, 1004, 1005, 1006, 1006, 1007, 1007, 1008,

1008, 1009, 1009, 1010, 1010, 1011, 1011, 1012,

1012, 1013, 1013, 1014, 1014, 1015, 1015, 1015,

1016, 1016, 1017, 1017, 1017, 1018, 1018, 1018,

1019, 1019, 1019, 1019, 1020, 1020, 1020, 1020,

1021, 1021, 1021, 1021, 1022, 1022, 1022, 1022,

1022, 1022, 1023, 1023, 1023, 1023, 1023, 1023,

1023, 1023, 1023, 1023, 1023, 1023, 1023, 1023,

1023, 1023, 1023, 1023, 1023, 1023, 1023, 1023,

1023, 1023, 1023, 1023, 1023, 1023, 1023, 1022,

1022, 1022, 1022, 1022, 1022, 1021, 1021, 1021,

1021, 1020, 1020, 1020, 1020, 1019, 1019, 1019,

1019, 1018, 1018, 1018, 1017, 1017, 1017, 1016,

1016, 1015, 1015, 1015, 1014, 1014, 1013, 1013,

1012, 1012, 1011, 1011, 1010, 1010, 1009, 1009,

1008, 1008, 1007, 1007, 1006, 1006, 1005, 1004,

1004, 1003, 1003, 1002, 1001, 1001, 1000, 999,

999, 998, 997, 997, 996, 995, 994, 994,

993, 992, 991, 990, 990, 989, 988, 987,

986, 986, 985, 984, 983, 982, 981, 980,

979, 978, 978, 977, 976, 975, 974, 973,

972, 971, 970, 969, 968, 967, 966, 965,

964, 963, 962, 960, 959, 958, 957, 956,

955, 954, 953, 951, 950, 949, 948, 947,

946, 944, 943, 942, 941, 939, 938, 937,

936, 934, 933, 932, 930, 929, 928, 927,

925, 924, 922, 921, 920, 918, 917, 916,

914, 913, 911, 910, 908, 907, 906, 904,

903, 901, 900, 898, 897, 895, 894, 892,

890, 889, 887, 886, 884, 883, 881, 879,

878, 876, 875, 873, 871, 870, 868, 866,

865, 863, 861, 860, 858, 856, 854, 853,

851, 849, 847, 846, 844, 842, 840, 839,

837, 835, 833, 831, 829, 828, 826, 824,

822, 820, 818, 816, 814, 813, 811, 809,

807, 805, 803, 801, 799, 797, 795, 793,

791, 789, 787, 785, 783, 781, 779, 777,

775, 773, 771, 769, 767, 765, 762, 760,

758, 756, 754, 752, 750, 748, 745, 743,

741, 739, 737, 735, 732, 730, 728, 726,

724, 721, 719, 717, 715, 712, 710, 708,

706, 703, 701, 699, 696, 694, 692, 690,

687, 685, 683, 680, 678, 675, 673, 671,

668, 666, 664, 661, 659, 656, 654, 652,

649, 647, 644, 642, 639, 637, 634, 632,

629, 627, 625, 622, 620, 617, 615, 612,

609, 607, 604, 602, 599, 597, 594, 592,

589, 587, 584, 581, 579, 576, 574, 571,

568, 566, 563, 561, 558, 555, 553, 550,

547, 545, 542, 539, 537, 534, 531, 529,

526, 523, 521, 518, 515, 512, 510, 507,

504, 501, 499, 496, 493, 491, 488, 485,

482, 479, 477, 474, 471, 468, 466, 463,

460, 457, 454, 451, 449, 446, 443, 440,

437, 434, 432, 429, 426, 423, 420, 417,

414, 412, 409, 406, 403, 400, 397, 394,

391, 388, 386, 383, 380, 377, 374, 371,

368, 365, 362, 359, 356, 353, 350, 347,

344, 342, 339, 336, 333, 330, 327, 324,

321, 318, 315, 312, 309, 306, 303, 300,

297, 294, 291, 288, 285, 282, 279, 276,

273, 270, 267, 264, 260, 257, 254, 251,

248, 245, 242, 239, 236, 233, 230, 227,

224, 221, 218, 215, 212, 209, 205, 202,

199, 196, 193, 190, 187, 184, 181, 178,

175, 171, 168, 165, 162, 159, 156, 153,

150, 147, 144, 140, 137, 134, 131, 128,

125, 122, 119, 115, 112, 109, 106, 103,

100, 97, 94, 90, 87, 84, 81, 78,

75, 72, 69, 65, 62, 59, 56, 53,

50, 47, 43, 40, 37, 34, 31, 28,

25, 21, 18, 15, 12, 9, 6, 3,

0, -3, -6, -9, -12, -15, -18, -21,

-25, -28, -31, -34, -37, -40, -43, -47,

-50, -53, -56, -59, -62, -65, -69, -72,

-75, -78, -81, -84, -87, -90, -94, -97,

-100, -103, -106, -109, -112, -115, -119, -122,

-125, -128, -131, -134, -137, -140, -144, -147,

-150, -153, -156, -159, -162, -165, -168, -171,

-175, -178, -181, -184, -187, -190, -193, -196,

-199, -202, -205, -209, -212, -215, -218, -221,

-224, -227, -230, -233, -236, -239, -242, -245,

-248, -251, -254, -257, -260, -264, -267, -270,

-273, -276, -279, -282, -285, -288, -291, -294,

-297, -300, -303, -306, -309, -312, -315, -318,

-321, -324, -327, -330, -333, -336, -339, -342,

-344, -347, -350, -353, -356, -359, -362, -365,

-368, -371, -374, -377, -380, -383, -386, -388,

-391, -394, -397, -400, -403, -406, -409, -412,

-414, -417, -420, -423, -426, -429, -432, -434,

-437, -440, -443, -446, -449, -451, -454, -457,

-460, -463, -466, -468, -471, -474, -477, -479,

-482, -485, -488, -491, -493, -496, -499, -501,

-504, -507, -510, -512, -515, -518, -521, -523,

-526, -529, -531, -534, -537, -539, -542, -545,

-547, -550, -553, -555, -558, -561, -563, -566,

-568, -571, -574, -576, -579, -581, -584, -587,

-589, -592, -594, -597, -599, -602, -604, -607,

-609, -612, -615, -617, -620, -622, -625, -627,

-629, -632, -634, -637, -639, -642, -644, -647,

-649, -652, -654, -656, -659, -661, -664, -666,

-668, -671, -673, -675, -678, -680, -683, -685,

-687, -690, -692, -694, -696, -699, -701, -703,

-706, -708, -710, -712, -715, -717, -719, -721,

-724, -726, -728, -730, -732, -735, -737, -739,

-741, -743, -745, -748, -750, -752, -754, -756,

-758, -760, -762, -765, -767, -769, -771, -773,

-775, -777, -779, -781, -783, -785, -787, -789,

-791, -793, -795, -797, -799, -801, -803, -805,

-807, -809, -811, -813, -814, -816, -818, -820,

-822, -824, -826, -828, -829, -831, -833, -835,

-837, -839, -840, -842, -844, -846, -847, -849,

-851, -853, -854, -856, -858, -860, -861, -863,

-865, -866, -868, -870, -871, -873, -875, -876,

-878, -879, -881, -883, -884, -886, -887, -889,

-890, -892, -894, -895, -897, -898, -900, -901,

-903, -904, -906, -907, -908, -910, -911, -913,

-914, -916, -917, -918, -920, -921, -922, -924,

-925, -927, -928, -929, -930, -932, -933, -934,

-936, -937, -938, -939, -941, -942, -943, -944,

-946, -947, -948, -949, -950, -951, -953, -954,

-955, -956, -957, -958, -959, -960, -962, -963,

-964, -965, -966, -967, -968, -969, -970, -971,

-972, -973, -974, -975, -976, -977, -978, -978,

-979, -980, -981, -982, -983, -984, -985, -986,

-986, -987, -988, -989, -990, -990, -991, -992,

-993, -994, -994, -995, -996, -997, -997, -998,

-999, -999, -1000, -1001, -1001, -1002, -1003, -1003,

-1004, -1004, -1005, -1006, -1006, -1007, -1007, -1008,

-1008, -1009, -1009, -1010, -1010, -1011, -1011, -1012,

-1012, -1013, -1013, -1014, -1014, -1015, -1015, -1015,

-1016, -1016, -1017, -1017, -1017, -1018, -1018, -1018,

-1019, -1019, -1019, -1019, -1020, -1020, -1020, -1020,

-1021, -1021, -1021, -1021, -1022, -1022, -1022, -1022,

-1022, -1022, -1023, -1023, -1023, -1023, -1023, -1023,

-1023, -1023, -1023, -1023, -1023, -1023, -1023, -1023,

-1024, -1023, -1023, -1023, -1023, -1023, -1023, -1023,

-1023, -1023, -1023, -1023, -1023, -1023, -1023, -1022,

-1022, -1022, -1022, -1022, -1022, -1021, -1021, -1021,

-1021, -1020, -1020, -1020, -1020, -1019, -1019, -1019,

-1019, -1018, -1018, -1018, -1017, -1017, -1017, -1016,

-1016, -1015, -1015, -1015, -1014, -1014, -1013, -1013,

-1012, -1012, -1011, -1011, -1010, -1010, -1009, -1009,

-1008, -1008, -1007, -1007, -1006, -1006, -1005, -1004,

-1004, -1003, -1003, -1002, -1001, -1001, -1000, -999,

-999, -998, -997, -997, -996, -995, -994, -994,

-993, -992, -991, -990, -990, -989, -988, -987,

-986, -986, -985, -984, -983, -982, -981, -980,

-979, -978, -978, -977, -976, -975, -974, -973,

-972, -971, -970, -969, -968, -967, -966, -965,

-964, -963, -962, -960, -959, -958, -957, -956,

-955, -954, -953, -951, -950, -949, -948, -947,

-946, -944, -943, -942, -941, -939, -938, -937,

-936, -934, -933, -932, -930, -929, -928, -927,

-925, -924, -922, -921, -920, -918, -917, -916,

-914, -913, -911, -910, -908, -907, -906, -904,

-903, -901, -900, -898, -897, -895, -894, -892,

-890, -889, -887, -886, -884, -883, -881, -879,

-878, -876, -875, -873, -871, -870, -868, -866,

-865, -863, -861, -860, -858, -856, -854, -853,

-851, -849, -847, -846, -844, -842, -840, -839,

-837, -835, -833, -831, -829, -828, -826, -824,

-822, -820, -818, -816, -814, -813, -811, -809,

-807, -805, -803, -801, -799, -797, -795, -793,

-791, -789, -787, -785, -783, -781, -779, -777,

-775, -773, -771, -769, -767, -765, -762, -760,

-758, -756, -754, -752, -750, -748, -745, -743,

-741, -739, -737, -735, -732, -730, -728, -726,

-724, -721, -719, -717, -715, -712, -710, -708,

-706, -703, -701, -699, -696, -694, -692, -690,

-687, -685, -683, -680, -678, -675, -673, -671,

-668, -666, -664, -661, -659, -656, -654, -652,

-649, -647, -644, -642, -639, -637, -634, -632,

-629, -627, -625, -622, -620, -617, -615, -612,

-609, -607, -604, -602, -599, -597, -594, -592,

-589, -587, -584, -581, -579, -576, -574, -571,

-568, -566, -563, -561, -558, -555, -553, -550,

-547, -545, -542, -539, -537, -534, -531, -529,

-526, -523, -521, -518, -515, -512, -510, -507,

-504, -501, -499, -496, -493, -491, -488, -485,

-482, -479, -477, -474, -471, -468, -466, -463,

-460, -457, -454, -451, -449, -446, -443, -440,

-437, -434, -432, -429, -426, -423, -420, -417,

-414, -412, -409, -406, -403, -400, -397, -394,

-391, -388, -386, -383, -380, -377, -374, -371,

-368, -365, -362, -359, -356, -353, -350, -347,

-344, -342, -339, -336, -333, -330, -327, -324,

-321, -318, -315, -312, -309, -306, -303, -300,

-297, -294, -291, -288, -285, -282, -279, -276,

-273, -270, -267, -264, -260, -257, -254, -251,

-248, -245, -242, -239, -236, -233, -230, -227,

-224, -221, -218, -215, -212, -209, -205, -202,

-199, -196, -193, -190, -187, -184, -181, -178,

-175, -171, -168, -165, -162, -159, -156, -153,

-150, -147, -144, -140, -137, -134, -131, -128,

-125, -122, -119, -115, -112, -109, -106, -103,

-100, -97, -94, -90, -87, -84, -81, -78,

-75, -72, -69, -65, -62, -59, -56, -53,

-50, -47, -43, -40, -37, -34, -31, -28,

-25, -21, -18, -15, -12, -9, -6, -3

};

*/

void setup()

{

pinMode(PWM_PIN, OUTPUT);

// Set up Timer 2 to do pulse width modulation on the speaker

// pin.

// Use internal clock (datasheet p.160)

ASSR &= ~(_BV(EXCLK) | _BV(AS2));

// Set fast PWM mode (p.157)

TCCR2A |= _BV(WGM21) | _BV(WGM20);

TCCR2B &= ~_BV(WGM22);

// Do non-inverting PWM on pin OC2B (p.155)

// On the Arduino this is pin 3.

TCCR2A = (TCCR2A | _BV(COM2B1)) & ~_BV(COM2B0);

TCCR2A &= ~(_BV(COM2A1) | _BV(COM2A0));

// No prescaler (p.158)

TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

// Set initial pulse width to the first sample.

PWM_VALUE = 0x80;

// Set up Timer 1 to send a sample every interrupt.

cli();

// disable Timer0 - this means that delay() is no longer available

TIMSK0 &= (~TOIE0);

// Set CTC mode (Clear Timer on Compare Match) (p.133)

// Have to set OCR1A *after*, otherwise it gets reset to 0!

TCCR1B = (TCCR1B & ~_BV(WGM13)) | _BV(WGM12);

TCCR1A = TCCR1A & ~(_BV(WGM11) | _BV(WGM10));

// No prescaler (p.134)

TCCR1B = (TCCR1B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

// Set the compare register (OCR1A).

// OCR1A is a 16-bit register, so we have to do this with

// interrupts disabled to be safe.

OCR1A = 976; // 16e6 / 16384

// Enable interrupt when TCNT1 == OCR1A (p.136)

TIMSK1 |= _BV(OCIE1A);

// set up the initial values for all the controls

g_env_lengths[0] = 0;

g_env_lengths[1] = 0;

g_env_type=0;

g_base_freq = 440;

g_freq_ramp_cnt = 0;

g_lpf_resonance = 0;

g_vib_strength = 0;

// set the parameters but don't start playing

reset_sample();

// play notes

pinMode(TONE1_PIN, INPUT);

digitalWrite(TONE1_PIN, HIGH);

pinMode(TONE2_PIN, INPUT);

digitalWrite(TONE2_PIN, HIGH);

pinMode(TONE3_PIN, INPUT);

digitalWrite(TONE3_PIN, HIGH);

pinMode(TONE4_PIN, INPUT);

digitalWrite(TONE4_PIN, HIGH);

pinMode(TONE5_PIN, INPUT);

digitalWrite(TONE5_PIN, HIGH);

g_button_status = 0; // no buttons are pressed

g_current_pitch_bit = 0; // no buttons are pressed

// low-pass

pinMode(LOWPASS_PIN, INPUT);

digitalWrite(LOWPASS_PIN, HIGH);

// distortion

pinMode(FREQ_PIN, INPUT);

digitalWrite(FREQ_PIN, HIGH);

// distortion

pinMode(DIST_PIN, INPUT);

digitalWrite(DIST_PIN, HIGH);

g_dist_status = 0; // not pressed

// tremolo

pinMode(TREM_PIN, INPUT);

digitalWrite(TREM_PIN, HIGH);

g_trem_status = 0; // not pressed

// now enable interrupts

sei();

}

static unsigned char get_button_status()

{

unsigned char ans = 0;

if (digitalRead(TONE1_PIN) == LOW) ans |= 0x01;

if (digitalRead(TONE2_PIN) == LOW) ans |= 0x02;

if (digitalRead(TONE3_PIN) == LOW) ans |= 0x04;

if (digitalRead(TONE4_PIN) == LOW) ans |= 0x08;

if (digitalRead(TONE5_PIN) == LOW) ans |= 0x10;

return ans;

}

static unsigned short get_base_freq(unsigned char status)

{

if (status & 0x10) return 320;

if (status & 0x08) return 360;

if (status & 0x04) return 400;

if (status & 0x02) return 480;

return 540;

}

void loop()

{

uint8_t new_status;

uint8_t tmp;

uint8_t tmp_pitch_bit;

//

// the loop updates the sound parameters

//

// since we don't want all the parameters updated when playing,

// some parameters are updated only on silence and on sustain,

// and others are updated only on silence

//

// envelopes are updated only on silence and sustain

if ((g_env_stage != 0) && (g_env_stage != 2)) {

g_env_lengths[0] = analogRead(ATTACK_CTRL) * 16;

g_env_lengths[1] = analogRead(RELEASE_CTRL) * 16;

g_env_type =

(digitalRead(LOWPASS_PIN) == LOW) ? 1 :

((digitalRead(FREQ_PIN) == LOW) ? 2 : 0);

}

// vibrato and resonance are always welcome

tmp = (uint8_t)(analogRead(VIBRATO_CTRL) / 4);

g_vib_strength = (tmp > 20) ? tmp : 0;

tmp = analogRead(RESONANCE_CTRL) / 4;

g_lpf_resonance = (tmp > 20) ? tmp : 0;

// so are tremolo and distortion

g_trem_status = digitalRead(TREM_PIN)==LOW ? 1 : 0;

g_dist_status = digitalRead(DIST_PIN)==LOW ? 1 : 0;

//

// pitch buttons

//

new_status = get_button_status();

// is the current pitch released?

if ((g_env_stage < 2) && ((g_current_pitch_bit & new_status) == 0)) {

g_env_stage = 2;

}

// are all buttons released?

if (new_status == 0) {

g_current_pitch_bit = 0x00;

}

// or is a different pitch selected?

else if (new_status != g_button_status) {

tmp_pitch_bit = g_current_pitch_bit;

// if a new button is pressed - select it

if (new_status & (~g_button_status)) {

tmp_pitch_bit = new_status & (~g_button_status);

}

// or if the current pitch is released - select another

else if ((new_status & (~g_current_pitch_bit)) == 0) {

tmp_pitch_bit = new_status;

}

// select only one pitch

tmp_pitch_bit &= (~(tmp_pitch_bit-1));

// if it's really a different pitch, play it

if (tmp_pitch_bit != g_current_pitch_bit) {

g_current_pitch_bit = tmp_pitch_bit;

// change the pitch with interrupts disabled

cli();

g_base_freq = get_base_freq(g_current_pitch_bit);

reset_sample();

g_env_stage = 0;

sei();

}

}

g_button_status = new_status;

}

static void reset_sample()

{

g_phase = 0;

g_freq_ramp_cnt = 0;

g_curr_freq = g_base_freq;

if (g_env_type == 2) {

g_curr_freq = g_base_freq / (g_env_lengths[0]/64 + 1);

if (g_curr_freq < 80) g_curr_freq = 80;

}

// reset filters

g_lpf_prev = 0;

g_lpf_prev_delta = 0;

g_lpf_freq = ((g_env_type == 1) ? 1 : 255); // zero if lpf envelope, else max

// reset vibrato

g_vib_phase = 0;

g_vib_fix_accum = 0;

// reset tremolo, distortion, and shit

g_interrupt_cnt = 0;

// reset envelope

g_env_stage=3;

g_env_time=0;

}

/* interrupt handler - that's where the synthesis happens */

SIGNAL(PWM_INTERRUPT)

{

short sample;

unsigned short fp;

unsigned char env_vol = 0xff;

unsigned char tmp;

unsigned char* p_env_item;

unsigned short vibrated_freq;

short vib_fix;

// use another oscillator with a lower frequency for the vibrato

g_vib_phase += 20;

if(g_vib_strength)

{

// vib_fix should be between -0x80 and 0x7f

g_vib_fix_accum += phase_to_delta[g_vib_phase/0x4000];

vib_fix = ((g_vib_fix_accum / 0x80) * (short)g_vib_strength) / 0x10;

// fix the frequency according to the vibrato

if ((vib_fix < 0) && ((unsigned short)(-vib_fix) >= g_curr_freq)) {

vibrated_freq = 1;

}

else {

vibrated_freq = g_curr_freq + vib_fix;

}

}

else {

vibrated_freq = g_curr_freq;

}

//

// volume/low-pass envelope

//

p_env_item = (g_env_type==0) ? &env_vol : &g_lpf_freq;

// this is performed anyway - for all env types

if (g_env_stage == 3) {

// at stage three there's nothing to play

*p_env_item = 0;

env_vol = 0;

}

else if (g_env_type < 2) {

// compute by stage, keeping *p_env_item between zero and 0xff

if (g_env_stage == 0) {

g_env_time++;

if (g_env_time >= g_env_lengths[0]) {

g_env_time = 0;

g_env_stage = 1;

}

*p_env_item=(unsigned char)(g_env_time / (g_env_lengths[0]/0x100 + 1));

}

else if (g_env_stage == 2) {

g_env_time++;

if (g_env_time >= g_env_lengths[1]) {

g_env_time = 0;

g_env_stage = 3;

}

// p_env_item can only decrease on stage 2

tmp = 255-(unsigned char)(g_env_time/ (g_env_lengths[1]/0x100 + 1));

if (tmp < *p_env_item) {

*p_env_item = tmp;

}

}

else { // g_env_stage == 1

*p_env_item = 255;

}

}

g_interrupt_cnt++;

// tremolo adjustments

if (g_trem_status) {

// do the shit at ~16Hz

if (g_interrupt_cnt & 0x200) {

env_vol /= 2;

}

}

// distortion adjustments

if (g_dist_status) {

env_vol &= g_rand_shit[g_interrupt_cnt & 0xFF];

}

//

// phase of the current wave

//

g_phase += vibrated_freq;

if (g_phase & 0xC000)

{

g_phase &= 0x3FFF;

//

// wave length wraparound

// this is a good time to make changes in the frequency

//

// fix the frequency according to the ramp

if (g_env_type == 2) {

if (g_env_stage == 0) {

g_freq_ramp_cnt += (0xff - g_env_lengths[0]/64);

g_curr_freq += 3+(g_freq_ramp_cnt/32);

g_freq_ramp_cnt &= 0x001f;

if (g_curr_freq > g_base_freq) {

g_curr_freq = g_base_freq;

g_env_stage = 1;

g_freq_ramp_cnt = 0;

}

}

else if (g_env_stage == 1) {

g_curr_freq = g_base_freq;

}

else if (g_env_stage == 2) {

g_freq_ramp_cnt += (0xff - g_env_lengths[1]/64);

g_curr_freq += 5+(g_freq_ramp_cnt/32);

g_freq_ramp_cnt &= 0x001f;

if (g_curr_freq >= 4000) {

g_env_stage = 3;

}

}

else if (g_env_stage == 3) {

env_vol = 0;

}

}

}

//

// current sample computation

//

// base waveform

fp = g_phase >> 3; // keep fp between zero and 2047

sample = 0;

if (g_wave_type < 2)

{

if (g_wave_type == 0) { // rough sawtooth

sample = (short)1023-(short)fp;

}

else { // sawtooth

sample = (fp < 1024) ? (short)1023-(short)fp*2 : (short)fp*2-3072;

}

}

//else if (g_wave_type == 2) { // sine

// sample = (short)pgm_read_word(&mysin_table[fp]);

//}

else { // square

sample = (fp & 1024) ? 1023 : -1023;

}

// sample is between -1024 and 1023

//

// low-pass filter

//

// start with the resonance - multiply g_lpf_prev_delta by the factor

g_lpf_prev_delta /= 0x10;

g_lpf_prev_delta *= g_lpf_resonance;

g_lpf_prev_delta /= 0x10;

//

// now add the low-pass part

//

// since sample and g_lpf_prev are both between -1024 and 1023,

// we can be sure that g_lpf_prev_delta will not be

// incremented/decremented by more than 2047

//

g_lpf_prev_delta +=

((((short)sample-(short)g_lpf_prev) / 0x10) * (short)g_lpf_freq) / 0x10;

if (g_lpf_prev_delta > 2047) g_lpf_prev_delta = 2047;

else if (g_lpf_prev_delta < -2048) g_lpf_prev_delta = -2048;

// accumulate it to the filter's output

g_lpf_prev += g_lpf_prev_delta;

if (g_lpf_prev > 1023) g_lpf_prev = 1023;

if (g_lpf_prev < -1024) g_lpf_prev = -1024;

// filter output

sample = g_lpf_prev;

// now sample is between -1024 and 1023

// scale it between -128 and 127

sample = sample / 8;

// adjust with the volume envelope

sample *= env_vol;

sample = sample / 256;

PWM_VALUE=(unsigned char)(sample + 128);

}