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/*
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"Tri-Shape", a wave shaping oscilatorfor Ginkosynthese's "grains" module.
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By Kassen Oud
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LICENSE:
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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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, see <http://www.gnu.org/licenses/>.
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DESCRIPION;
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A triangle-based osclitator with wave-folding and hard-clipping features.
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MANUAL;
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Knob 1 / mod 1; Wave folding
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Amplifies the base triangle wave, then once it hits the limits of the
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range "folds" it back in the opposite direction. With enough
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amplification this will happen again at the other side, creating a
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rich spectrum.
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Knob 2/ mod 2; Hard Cliping
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Amplifies the signal (after the folding) and clips the result. This is
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done asymetrically for a "deeper" and more "balsy" sound. Thanks to
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Rob Bothof for that trick.
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Knob 3: Base Tuning.
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Sets the base pitch.
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Mod 3; Pitch Modulation
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This CV gets added to the value set by Knob 3.
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*/
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//the libraries we use
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <avr/pgmspace.h>
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//variables
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uint16_t phase_accumulator; //keeps track of the phase
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uint16_t phase_inc; //phase increase per sample
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bool flip = false; //keeps track of the output's polarity
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uint16_t wrap = 1; // amount of wave-folding
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uint16_t drive = 32; //amount of clipping for positive signal
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uint16_t top_drive = 32; //same for negative signal
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uint16_t output = 127; //the value we write out
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uint16_t last_out = 127; //last value we wrote out
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// Map inputs
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#define DRIVE_CONTROL (A1)
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#define WRAP_CONTROL (A2)
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#define PITCH_KNOB (A0)
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#define PITCH_CV (A3)
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// Changing these will also requires rewriting setup()
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// Output is on pin 11
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#define PWM_PIN 11
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#define PWM_VALUE OCR2A
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#define LED_PORT PORTB
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#define LED_BIT 5
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#define PWM_INTERRUPT TIMER2_OVF_vect
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//maps cv to samples of phase increase each time we output a new value
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//this might need tuning in the future
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const uint16_t freqTable[] PROGMEM = {
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69, 69, 69, 69, 70, 70, 70, 70, 70, 71, // 0 to 9
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71, 71, 71, 72, 72, 72, 72, 73, 73, 73, //
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73, 74, 74, 74, 74, 75, 75, 75, 75, 76, //
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76, 76, 76, 77, 77, 77, 77, 78, 78, 78, //
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78, 79, 79, 79, 79, 80, 80, 80, 81, 81, //
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81, 81, 82, 82, 82, 82, 83, 83, 83, 84, //
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84, 84, 84, 85, 85, 85, 86, 86, 86, 86, //
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87, 87, 87, 88, 88, 88, 88, 89, 89, 89, //
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90, 90, 90, 91, 91, 91, 91, 92, 92, 92, //
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93, 93, 93, 94, 94, 94, 95, 95, 95, 96, //
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96, 96, 97, 97, 97, 97, 98, 98, 98, 99, // 100 to 109
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99, 99, 100, 100, 100, 101, 101, 101, 102, 102, //
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102, 103, 103, 104, 104, 104, 105, 105, 105, 106, //
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106, 106, 107, 107, 107, 108, 108, 109, 109, 109, //
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110, 110, 110, 111, 111, 111, 112, 112, 113, 113, //
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113, 114, 114, 114, 115, 115, 116, 116, 116, 117, //
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117, 118, 118, 118, 119, 119, 120, 120, 120, 121, //
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121, 122, 122, 122, 123, 123, 124, 124, 124, 125, //
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125, 126, 126, 127, 127, 127, 128, 128, 129, 129, //
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130, 130, 130, 131, 131, 132, 132, 133, 133, 134, //
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134, 134, 135, 135, 136, 136, 137, 137, 138, 138, // 200 to 209
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139, 139, 139, 140, 140, 141, 141, 142, 142, 143, //
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143, 144, 144, 145, 145, 146, 146, 147, 147, 148, //
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148, 149, 149, 150, 150, 151, 151, 152, 152, 153, //
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153, 154, 154, 155, 155, 156, 156, 157, 157, 158, //
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158, 159, 159, 160, 161, 161, 162, 162, 163, 163, //
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164, 164, 165, 165, 166, 167, 167, 168, 168, 169, //
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169, 170, 171, 171, 172, 172, 173, 173, 174, 175, //
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175, 176, 176, 177, 178, 178, 179, 179, 180, 181, //
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181, 182, 182, 183, 184, 184, 185, 185, 186, 187, //
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187, 188, 189, 189, 190, 190, 191, 192, 192, 193, // 300 to 309
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194, 194, 195, 196, 196, 197, 198, 198, 199, 200, //
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200, 201, 202, 202, 203, 204, 204, 205, 206, 206, //
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207, 208, 208, 209, 210, 211, 211, 212, 213, 213, //
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214, 215, 216, 216, 217, 218, 218, 219, 220, 221, //
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221, 222, 223, 224, 224, 225, 226, 227, 227, 228, //
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229, 230, 231, 231, 232, 233, 234, 234, 235, 236, //
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237, 238, 238, 239, 240, 241, 242, 242, 243, 244, //
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245, 246, 246, 247, 248, 249, 250, 251, 251, 252, //
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253, 254, 255, 256, 257, 257, 258, 259, 260, 261, //
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262, 263, 264, 264, 265, 266, 267, 268, 269, 270, // 400 to 409
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271, 272, 273, 273, 274, 275, 276, 277, 278, 279, //
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280, 281, 282, 283, 284, 285, 286, 287, 288, 288, //
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289, 290, 291, 292, 293, 294, 295, 296, 297, 298, //
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299, 300, 301, 302, 303, 304, 305, 306, 307, 308, //
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310, 311, 312, 313, 314, 315, 316, 317, 318, 319, //
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320, 321, 322, 323, 324, 325, 327, 328, 329, 330, //
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331, 332, 333, 334, 335, 337, 338, 339, 340, 341, //
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342, 343, 345, 346, 347, 348, 349, 350, 352, 353, //
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354, 355, 356, 357, 359, 360, 361, 362, 363, 365, //
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366, 367, 368, 370, 371, 372, 373, 375, 376, 377, // 500 to 509
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378, 380, 381, 382, 383, 385, 386, 387, 389, 390, //
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391, 393, 394, 395, 397, 398, 399, 401, 402, 403, //
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405, 406, 407, 409, 410, 411, 413, 414, 416, 417, //
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418, 420, 421, 423, 424, 425, 427, 428, 430, 431, //
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433, 434, 436, 437, 438, 440, 441, 443, 444, 446, //
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447, 449, 450, 452, 453, 455, 456, 458, 460, 461, //
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463, 464, 466, 467, 469, 470, 472, 474, 475, 477, //
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478, 480, 482, 483, 485, 486, 488, 490, 491, 493, //
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495, 496, 498, 500, 501, 503, 505, 506, 508, 510, //
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511, 513, 515, 517, 518, 520, 522, 524, 525, 527, // 600 to 609
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529, 531, 532, 534, 536, 538, 540, 541, 543, 545, //
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547, 549, 551, 552, 554, 556, 558, 560, 562, 564, //
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566, 567, 569, 571, 573, 575, 577, 579, 581, 583, //
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585, 587, 589, 591, 593, 595, 597, 599, 601, 603, //
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605, 607, 609, 611, 613, 615, 617, 619, 621, 623, //
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625, 627, 630, 632, 634, 636, 638, 640, 642, 644, //
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647, 649, 651, 653, 655, 658, 660, 662, 664, 666, //
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669, 671, 673, 675, 678, 680, 682, 685, 687, 689, //
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691, 694, 696, 698, 701, 703, 705, 708, 710, 713, //
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715, 717, 720, 722, 725, 727, 729, 732, 734, 737, // 700 to 709
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739, 742, 744, 747, 749, 752, 754, 757, 759, 762, //
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764, 767, 770, 772, 775, 777, 780, 783, 785, 788, //
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791, 793, 796, 799, 801, 804, 807, 809, 812, 815, //
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817, 820, 823, 826, 828, 831, 834, 837, 840, 842, //
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845, 848, 851, 854, 857, 860, 862, 865, 868, 871, //
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874, 877, 880, 883, 886, 889, 892, 895, 898, 901, //
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904, 907, 910, 913, 916, 919, 922, 925, 928, 932, //
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935, 938, 941, 944, 947, 950, 954, 957, 960, 963, //
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966, 970, 973, 976, 979, 983, 986, 989, 993, 996, //
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999,1003,1006,1009,1013,1016,1020,1023,1027,1030, // 800 to 809
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1033,1037,1040,1044,1047,1051,1054,1058,1061,1065, //
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1069,1072,1076,1079,1083,1087,1090,1094,1098,1101, //
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1105,1109,1112,1116,1120,1124,1127,1131,1135,1139, //
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1143,1146,1150,1154,1158,1162,1166,1170,1174,1178, //
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1182,1186,1189,1193,1197,1201,1206,1210,1214,1218, //
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1222,1226,1230,1234,1238,1242,1247,1251,1255,1259, //
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1263,1268,1272,1276,1280,1285,1289,1293,1298,1302, //
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1306,1311,1315,1320,1324,1328,1333,1337,1342,1346, //
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1351,1355,1360,1365,1369,1374,1378,1383,1388,1392, //
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1397,1402,1406,1411,1416,1421,1425,1430,1435,1440, // 900 to 909
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1444,1449,1454,1459,1464,1469,1474,1479,1484,1489, //
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1494,1499,1504,1509,1514,1519,1524,1529,1534,1539, //
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1545,1550,1555,1560,1565,1571,1576,1581,1587,1592, //
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1597,1603,1608,1613,1619,1624,1630,1635,1641,1646, //
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1652,1657,1663,1668,1674,1679,1685,1691,1696,1702, //
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1708,1714,1719,1725,1731,1737,1742,1748,1754,1760, //
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1766,1772,1778,1784,1790,1796,1802,1808,1814,1820, //
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1826,1832,1838,1845,1851,1857,1863,1869,1876,1882, //
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1888,1895,1901,1907,1914,1920,1927,1933,1940,1946, //
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1953,1959,1966,1972,1979,1986,1992,1999,2006,2012, // 1000 to 1009
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2019,2026,2033,2040,2046,2053,2060,2067,2074,2081, // 1010 to 1019
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2088,2095,2102,2109 , // 1020 to 1023
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};
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uint16_t mapFreq(uint16_t input)
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{
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return pgm_read_word_near(freqTable + input);
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}
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//sets up pins and configures the samplerate and frequency of the PWM output
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void setup()
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{
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TCCR2A = _BV(COM2A1) | _BV(WGM20);
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TCCR2B = _BV(CS20);
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TIMSK2 = _BV(TOIE2);
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pinMode(PWM_PIN,OUTPUT);
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PWM_VALUE = 127;
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}
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//reads modulation inputs
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void loop()
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{
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//calculate the pitch
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int pwmv = min( 1023, analogRead(PITCH_CV) + analogRead(PITCH_KNOB));
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//look up the phase increase per sample
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phase_inc = mapFreq(pwmv);
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//read the control for wave-folding
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wrap = min( 64 + (analogRead(WRAP_CONTROL) >> 1), 511);
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//read the control for clipping and calculate the two amounts of overdrive
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drive = min( 32 + (analogRead(DRIVE_CONTROL) >> 1), 511);
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top_drive = max( 32, drive >>1);
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}
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//Actual sound generation happens here.
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//This involves rather a lot of bitwise operations, if you're looking to get
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//into writing code for the Grains I'd suggest not starting here; "PWM-Saw" is
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//far more "friendly". That's a nice way of saying "Here be Dragons".
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//I'm writing numbers out as literal trains of 0's and 1's because we make fair
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//ampount of use of those. Also note that a lot of the structure for this is
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//caused by avoiding signed integers, while we do want a symetrical signal.
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//Hence; we treat it as a unipolar signal, keep track of the polarity it should
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//be and apply that at the end.
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//I drew the process out on graph paper using multicoloured fineliner.
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//If you're serious about following all of this that might help.
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SIGNAL(PWM_INTERRUPT)
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{
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//increase the phase
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phase_accumulator += phase_inc;
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//2nd half of the phase will be the negative part of the cycle
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flip = phase_accumulator & 0b1000000000000000;
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//turn the phase acumulator into 4 up-ramps
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output = (phase_accumulator & 0b0011111111111111);
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//get these into 7 bit range. "flip" will be the 8th bit of the output
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output = output >> 7;
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//invert the 2nd and 4th of our 4 up-ramps to create our triangle wave
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if (phase_accumulator & 0b0100000000000000) output = (uint16_t)127 - output;
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//amplify the signal for the wave-wrapping
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output *= wrap;
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output = output >> 6;
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//detect whether folding will be more involved than inverting the range
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//from 128 to 254
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if (output & 0b1111111100000000)
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{
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//values between 255 and 511 fold back past the "0" line
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if (output & 0b0000000100000000) flip = !flip;
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//mask out bits beyond which the process just repeats
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output &= 0b0000000011111111;
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}
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//actual folding
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if (output > (uint16_t)127)
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{
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output = 127 - (output & 0b0000000001111111);
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}
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//apply the signal gain for asymetrical clipping
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output *= flip?drive:top_drive;
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output = output >> 5;
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//clip
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if (output > (uint16_t)127) output = (uint16_t)127;
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//turn our 7bit unipolar value into a 8bit bipolar one
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if ( flip ) output = (uint16_t)127 - output;
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else output += (uint16_t)127;
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//slight amount of smoothing
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output = (output + last_out) >> 1;
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last_out = output;
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//write out the output
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PWM_VALUE = output;
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}
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Reference in New Issue