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https://github.com/sjlongland/polyphonic-synthesizer.git
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107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
/*!
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* Polyphonic synthesizer for microcontrollers: Atmel ATTiny85 port.
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* (C) 2016 Stuart Longland
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*
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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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*
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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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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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* MA 02110-1301 USA
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*/
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#include "poly.h"
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#include "fifo.h"
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#include <avr/io.h>
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#include <util/delay.h>
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#include <avr/interrupt.h>
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#define SAMPLE_LEN 16
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static volatile uint8_t sample_buffer[SAMPLE_LEN];
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static struct fifo_t sample_fifo;
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int main(void) {
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struct poly_evt_t poly_evt;
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/* Turn on all except ADC */
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PRR = (1 << PRADC);
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/* Start up PLL */
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PLLCSR = (1 << PLLE);
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while (!(PLLCSR & (1<<PLOCK)));
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PLLCSR |= (1<<PCKE);
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fifo_init(&sample_fifo, sample_buffer, SAMPLE_LEN);
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/* Reset the synthesizer */
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poly_reset();
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/* Enable output on PB4 (PWM out) */
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DDRB |= (1 << 4) | (1 << 3);
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PORTB |= (1 << 4) | (1 << 3);
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/* Timer 1 configuration for PWM */
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OCR1B = 128; /* Initial PWM value */
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OCR1C = 255; /* Maximum PWM value */
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TCCR1 = (1 << CS10); /* No prescaling, max speed */
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GTCCR = (1 << PWM1B) /* Enable PWM */
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| (2 << COM1B0); /* Clear output bit on match */
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/* Timer 0 configuration for sample rate interrupt */
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TCCR0A = (2 << WGM00); /* CTC mode */
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TCCR0B = (1 << CS00); /* No prescaling */
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OCR0A = F_CPU / _POLY_FREQ; /* Sample rate */
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TIMSK |= (1 << OCIE0A); /* Enable interrupts */
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/* Configure the synthesizer */
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poly_evt.flags = POLY_EVT_TYPE_ENABLE;
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poly_evt.value = 1;
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poly_load(&poly_evt);
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poly_evt.flags = POLY_EVT_TYPE_IFREQ;
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poly_evt.value = 1000;
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poly_load(&poly_evt);
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poly_evt.flags = POLY_EVT_TYPE_IAMP;
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poly_evt.value = 255;
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poly_load(&poly_evt);
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poly_evt.flags = POLY_EVT_TYPE_ASCALE;
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poly_evt.value = 8;
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poly_load(&poly_evt);
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sei();
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while(1) {
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poly_evt.flags = POLY_EVT_TYPE_TIME;
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poly_evt.value = 64000;
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poly_load(&poly_evt);
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while (poly_remain) {
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while (sample_fifo.stored_sz < SAMPLE_LEN) {
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int16_t s = poly_next();
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fifo_write_one(&sample_fifo,
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128 + (s >> 9));
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}
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PORTB ^= (1 << 3);
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}
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}
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return 0;
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}
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ISR(TIM0_COMPA_vect) {
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uint8_t sample = fifo_read_one(&sample_fifo);
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if (sample >= 0)
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OCR1B = sample;
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else
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OCR1B = 128;
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}
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