134 lines
2.1 KiB
C
134 lines
2.1 KiB
C
#include <inttypes.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <util/delay.h>
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#include <stdlib.h>
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#include "main.h"
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volatile uint8_t sample_pending;
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// sample rate is 8M / (5 * 64) = 25000
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enum {
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synth_channel_count = 2
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};
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typedef struct {
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uint16_t phase;
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uint16_t speed;
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} synth_channel_t;
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typedef struct {
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synth_channel_t channels[synth_channel_count];
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uint16_t output;
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} synth_t;
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static synth_t synth;
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//25kHz
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ISR(TIMER0_OVF_vect)
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{
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PORTC ^= 0b1;
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OCR1B = (++OCR1B % 0x1000);
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sample_pending = 1;
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}
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static void synth_init(void)
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{
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// some test values
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synth.channels[0].phase = 0;
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synth.channels[0].speed = 1153;
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synth.channels[1].phase = 0;
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synth.channels[1].speed = 1728;
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}
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static inline void synth_mix(void)
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{
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synth.output = 0;
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for (int i = 0; i < synth_channel_count; i++) {
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synth_channel_t *chan = &synth.channels[i];
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chan->phase += chan->speed;
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synth.output += (chan->phase >> 8) & 0xff;
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}
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}
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static void init_sampletimer(void)
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{
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// Timer 0
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//
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//set timer0 to CTC & prescaler 64 == 125k
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TCCR0A = (1 << WGM01);
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TCCR0B = (1 << CS00) | (1 << CS01);
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//count up to 5 :
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OCR0A = 5;
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//enable interrupt
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TIMSK0 |= (1 << TOIE0);
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}
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static inline void init_pwm(void)
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{
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//PB2 set to output:
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DDRB |= (1 << PORTB2);
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OCR1B = 0x100; //preselect some default
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ICR1 = 0x1000; // TOP-wert
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TCCR1A = (1 << COM1B1) | (1 << WGM11); // only b-chan , fastpwm (mode 14)
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TCCR1B = (1 << WGM13) | (1 << WGM12) | (1 << CS10); //Fastpwm, no prescale
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return;
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}
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static void init_leds(void)
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{
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//enable LED channels as output
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DDRC |= (1 << PORTC0) | (1 << PORTC2) | (1 << PORTC3) | (1 << PORTC1);
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PORTC = 1; //one led is on...
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return;
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}
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inline void setleds(uint8_t state)
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{
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//set leds according to
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PORTC |= (state | 0b00001111);
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PORTC &= ~(state | 0b11110000);
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return;
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}
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static void init_motor(void)
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{
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//vibration motor on B1:
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DDRB |= (1 << PORTB1);
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}
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int main(void)
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{
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//hardware initialisation:
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init_leds();
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init_motor();
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init_pwm();
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init_sampletimer();
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sample_pending = 0;
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synth_init();
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sei();
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while(1);
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while(1) {
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while (0 == sample_pending) ;
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sample_pending = 0;
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synth_mix();
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}
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//never get here
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return 0;
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}
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