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106 lines
2.7 KiB
106 lines
2.7 KiB
#include <avr/io.h>
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#include "mmc.h"
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void timer_init_mega16(void)
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{
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ICR1 = (1 << 11) - 1;/* 11 bit pwm */
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OCR1A = 0;
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TCCR1A = (1 << COM1A1) | (1 << CS10) | (1 << WGM11);/* fast pwm, non inverted, top in ICR1 */
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TCCR1B = (1 << WGM13) | (1 << WGM12) | (1 << CS10);/* fast pwm, top in ICR1, */
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DDRD |= (1 << PD5);/* set pwm pin as output */
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TIMSK = 1 << TOIE1;/* interrupt at top */
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}
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void timer_init_tiny45(void)
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{
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PLLCSR = 1 << PLLE;/* pll enable */
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delay_us(100);
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while(!(PLLCSR & (1 << PLOCK))) {;}/* wait for lock */
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PLLCSR |= 1 << PCKE;/* use pll */
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OCR1C = 0xff;
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/* output pin: OC1A = PB1 = 6 */
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OCR1A = 0;
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TCCR1 = (1 << PWM1A) | (1 << COM1A1) | (1 << CS10);/* pwm enable, non inverted, no prescaler */
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DDRB |= (1 << PB1);
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/* output pin: OC1B = PB5 = 3 */
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//OCR1B = 0;
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//TCCR1 = (1 << CS10);/* no prescaler */
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//GTCCR = (1 << PWM1B) | (1 << COM1B1);/* pwm enable, non inverted */
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//DDRB |= (1 << PB5);
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TIMSK = 1 << TOIE1;/* interrupt on overflow */
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}
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void timer_init_tiny26(void)
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{
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PLLCSR = 1 << PLLE;/* pll enable */
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delay_us(100);
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while(!(PLLCSR & (1 << PLOCK))) {;}/* wait for lock */
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PLLCSR |= 1 << PCKE;/* use pll */
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OCR1C = 0xff;/* unused */
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/* output pin: OC1A = PB1 = 1 or OC1B = PB3 = 2 */
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OCR1A = 0;
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TCCR1A = (1 << COM1A1) (1 << PWM1A);/* pwm enable, not inverted */
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TCCR1B = (1 << CS10);/* fast pwm, no prescaler */
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DDRB |= (1 << PB1);
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TIMSK = 1 << TOIE1;/* interrupt on overflow */
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}
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uint8_t length[4];/* remaining samples */
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uint8_t mmc_position[4];/* current reading position on mmc */
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uint8_t overflows = 1;/* remaining counter overflows until next sample */
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#define SAMPLE_BITS 11
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#define BUFFER_SIZE 92
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#define REFRESH_AMOUNT 64
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#define REFRESH_SIZE (BUFFER_SIZE - REFRESH_AMOUNT)
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uint8_t buffer[BUFFER_SIZE];/* buffer for mmc data */
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uint8_t pos = 0;/* current playing position */
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uint8_t refresh_buffer = 0;/* position to start buffer refreshing */
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timerinterrupt()
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{
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//if(!(TIFR & (1 << TOV1))) {continue;}/* interrupt flag polling */
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//TIFR |= (1 << TOV1);/* done by hardware */
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overflows--;
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if(!overflows)
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{
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overflows = 1 << (SAMPLE_BITS - 8);
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pos = (pos + 1) % BUFFER_SIZE;
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}
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/* TODO: a-law decoding */
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/* TODO: 11bit PWM emulation */
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OCR1A = buffer[pos];/* play next sample */
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}
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void main(void)
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{
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if(mmc_init() != 0) {/* mmc fail */;}
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timer_init_tiny26();
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sei();
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for(;;)
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{
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if(pos == refresh_buffer)/* refresh buffer if running low */
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{
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mmc_read(mmc_position, buffer + (ref + REFRESH_SIZE) % BUFFER_SIZE, BUFFER_SIZE - ref, buffer, REFRESH_AMOUNT - (BUFFER_SIZE - ref));
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/* pos on sd , first buffer address , 1st buffer size ,2nd buf, 2nd buffer size */
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refresh_buffer = (refresh_buffer + REFRESH_AMOUNT) % BUFFER_SIZE;
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}
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}
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}
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