textadv/src/dac.c

/* Copyright © 2020 tyrolyean
 *
 * 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.h"
#include "dac.h"
#include "structures.h"

#include <stdbool.h>

uint8_t dac_mode = DAC_MODE_SINE;
int16_t dac_frequency_deviation = 0;

void write_to_dac(uint8_t addr, uint8_t data){


	set_addr(addr);
	DATA_DDR_REG = 0xFF;
	DATA_REG = data;
	CTRL_REG &= ~(1<<WR_SHIFT) & ~(1<<CS_DAC_SHIFT);

	_delay_us(BUS_HOLD_US);	/*Wait for the data and signal lanes to become stable*/

	CTRL_REG |= 1<<CS_DAC_SHIFT;
	CTRL_REG |= 1<<WR_SHIFT;
	return;
}

uint8_t read_from_dac(uint8_t addr){

	uint8_t data = 0x00;

	set_addr(addr);
	DATA_DDR_REG = 0x00;

	/* Sometimes the avr "forgets" to alter the port register for one cycle
	 * which usually isn't a problem but has lead to instability. Worthy 
	 * one clock cycle */
	DATA_REG = 0x00;
	CTRL_REG &= ~(1<<RD_SHIFT) & ~(1<<CS_DAC_SHIFT);

	_delay_us(BUS_HOLD_US);	/* Wait for the data and signal lanes to become
	                         * stable*/
	data = PINF;
	CTRL_REG |= 1<<CS_DAC_SHIFT | 1<<RD_SHIFT;
	return data;
}

void feed_dac(){
	/* Internal counter for positioning inside the currently playing
	 * waveform */
	static uint8_t threash = 0x00;
	/* Used to generate the desired frequency offset if the waveform should
	 * be made "longer" --> the frequency made lower from baseline 
	 */
	static int16_t freq_delay_cnt = 0x00;
	switch(dac_mode){
		
		default:
		case DAC_MODE_SILENT:
			for(uint8_t i = 0; i  < 0xFF; i++){
				write_to_dac(i%2, 0);
			}
			
		break;
		
		case DAC_MODE_SINE:
		/* Generates a sine from a predetermined sine table in program
		 * space */
			for(uint8_t i = 0; i  < (0xFF/2); i++){
				write_to_dac(1, 
					pgm_read_byte(&sine_table[threash]));
				write_to_dac(0, 
					pgm_read_byte(&sine_table[threash]));
				
				if(dac_frequency_deviation >=0){
					freq_delay_cnt++;
					if(freq_delay_cnt >=
						dac_frequency_deviation){
						freq_delay_cnt = 0;
						threash++;
						
					}
					
				}else{
					threash -= dac_frequency_deviation;
				}
				
			}
				break;
		case DAC_MODE_SQUARE:
		/* Generates a square wave tone */
			for(uint8_t i = 0; i  < (0xFF/2); i++){
				if(threash > (0xFF/2)){
					write_to_dac(0, 0xFF);
					write_to_dac(1, 0xFF);
				}else{
					write_to_dac(0, 0);
					write_to_dac(1, 0);
				}
				if(dac_frequency_deviation >=0){
					freq_delay_cnt++;
					if(freq_delay_cnt >=
						dac_frequency_deviation){
						freq_delay_cnt = 0;
						threash++;
						
					}
					
				}else{
					threash -= dac_frequency_deviation;
				}
			}
				break;
		case DAC_MODE_SAW:
			/* Generates a saw wave tone */
			for(uint8_t i = 0; i  < (0xFF/2); i++){
				write_to_dac(0, threash);
				write_to_dac(1, threash);
				if(dac_frequency_deviation >=0){
					freq_delay_cnt++;
					if(freq_delay_cnt >=
						dac_frequency_deviation){
						freq_delay_cnt = 0;
						threash++;
						
					}
					
				}else{
					threash -= dac_frequency_deviation;
				}
			}
		break;
		case DAC_MODE_NOISE:
		/* Generates white noise from a predetermined LUT
		 */
			for(uint8_t i = 0; i  < (0xFF/2); i++){
				static uint16_t noise_cnt = 0;
				write_to_dac(1, 
					pgm_read_byte(&noise_table[noise_cnt]));
				write_to_dac(0, 
					pgm_read_byte(&noise_table[noise_cnt]));
				
				noise_cnt++; /* Doesn't have frequency diversion 
				            */
				if(noise_cnt >= 1024){
					noise_cnt = 0;
				}
				
			}
				break;
		case DAC_MODE_TRIANGLE:
			/* Generates a triangle wave tone */
			for(uint8_t i = 0; i  < (0xFF/2); i++){
				static int8_t direction = 1;
				if((threash == 0xFF) | !threash){
					direction = -direction;
				}
				write_to_dac(0, threash);
				write_to_dac(1, threash);
				if(dac_frequency_deviation >=0){
					freq_delay_cnt++;
					if(freq_delay_cnt >=
						dac_frequency_deviation){
						freq_delay_cnt = 0;

						threash += direction;
						
					}
					
				}else{
					if((dac_frequency_deviation *    
                                                direction) > 
						(0xFF - threash)){
						threash = 0xFF;
						continue;
					}
					threash = (dac_frequency_deviation * 
						direction);
				}
			}
		break;
	}

	return;
}

void routine_dac(){
	
	uint8_t received = read_from_dac(0x00);
	if(!(received & (0x01<<0))){
		feed_dac();
	}
	return;	
}