/*
 avr-gcc \
     -mmcu=atmega168 -DF_CPU=8000000UL \
     -gdwarf-2 -std=gnu99 -Os -fwhole-program -flto -mstrict-X -fmerge-all-constants \
     -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums \
     -Wall -Wundef -Wno-main -Wno-comment -Werror=implicit-function-declaration \
     -fstack-usage -Wstack-usage=4 \
     -I. main.c \
     -o main.elf
 avrdude -p atmega168 -c usbasp   -U flash:w:main.elf
*/

#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define SHIFT_DS PB3
#define SHIFT_SH PB5
#define SHIFT_ST PB0

static uint8_t seg7data[4] = { 0, 0, 0, 0 };

static void shiftreg_set32() {
	for (signed int j = 3; j >= 0; j--) {
		uint8_t s = seg7data[j];
		for (signed int i = 7; i >= 0; i--) {
			if ((s >> i) & 1) {
				PORTB |= (1 << SHIFT_DS);
			} else {
				PORTB &= ~(1 << SHIFT_DS);
			}

			PORTB |= (1 << SHIFT_SH);
			PORTB &= ~(1 << SHIFT_SH);
		}
	}

	PORTB |= (1 << SHIFT_ST);
	PORTB &= ~(1 << SHIFT_ST);
}

static void shiftreg_zero32() {
	PORTB &= ~(1 << SHIFT_DS);
	for (int i = 0; i < 32; i++) {
		PORTB |= (1 << SHIFT_SH);
		PORTB &= ~(1 << SHIFT_SH);
	}
	PORTB |= (1 << SHIFT_ST);
	PORTB &= ~(1 << SHIFT_ST);
}

#define Db1 (1<<0)
#define De1 (1<<1)
#define Dd1 (1<<2)
#define Df1 (1<<3)
#define Da1 (1<<4)
#define Dg1 (1<<5)
#define Dp1 (1<<6)
#define Dc1 (1<<7)
#define Dp2 (1<<0)
#define De2 (1<<1)
#define Dc2 (1<<2)
#define Dg2 (1<<3)
#define Df2 (1<<4)
#define Db2 (1<<5)
#define Dd2 (1<<6)
#define Da2 (1<<7)

#define C10 (Da1 | Db1 | Dc1 | Dd1 | De1 | Df1)
#define C20 (Da2 | Db2 | Dc2 | Dd2 | De2 | Df2)

#define C11 (Db1 | Dc1)
#define C21 (Db2 | Dc2)

#define C12 (Da1 | Db1 | Dg1 | De1 | Dd1)
#define C22 (Da2 | Db2 | Dg2 | De2 | Dd2)

#define C13 (Da1 | Db1 | Dg1 | Dc1 | Dd1)
#define C23 (Da2 | Db2 | Dg2 | Dc2 | Dd2)

#define C14 (Df1 | Dg1 | Db1 | Dc1)
#define C24 (Df2 | Dg2 | Db2 | Dc2)

#define C15 (Da1 | Df1 | Dg1 | Dc1 | Dd1)
#define C25 (Da2 | Df2 | Dg2 | Dc2 | Dd2)

#define C16 (Da1 | Df1 | Dg1 | Dc1 | Dd1 | De1)
#define C26 (Da2 | Df2 | Dg2 | Dc2 | Dd2 | De2)

#define C17 (Da1 | Db1 | Dc1)
#define C27 (Da2 | Db2 | Dc2)

#define C18 (Da1 | Db1 | Dc1 | Dd1 | De1 | Df1 | Dg1)
#define C28 (Da2 | Db2 | Dc2 | Dd2 | De2 | Df2 | Dg2)

#define C19 (Dg1 | Df1 | Da1 | Db1 | Dc1 | Dd1)
#define C29 (Dg2 | Df2 | Da2 | Db2 | Dc2 | Dd2)

static const __flash uint16_t num1[10] = { C10, C11, C12, C13, C14, C15, C16, C17, C18, C19 };
static const __flash uint16_t num2[10] = { C20, C21, C22, C23, C24, C25, C26, C27, C28, C29 };

static void disp_num(uint8_t which /* 0 or 1 */, uint8_t num) {
	uint8_t nh = num2[num / 10];
	uint8_t nl = num1[num % 10];

	seg7data[which*2 + 0] = nl;
	seg7data[which*2 + 1] = nh;
}

volatile uint16_t duty1 = 1500;
volatile uint16_t duty2 = 1500;
ISR(TIMER1_COMPA_vect) {
	if (!OCR1A) {
		OCR1A = duty2;
	} else {
		OCR1A = 0;
	}
}
ISR(TIMER1_COMPB_vect) {
	if (!OCR1B) {
		OCR1B = duty1;
	} else {
		OCR1B = 0;
	}
}

/* Converts poti value from ADC-range to microseconds 0.5 ... 2.5 */
static uint16_t adc2us(uint16_t av) {
	return 500 + (((uint32_t)av * 2000) >> 10);
}

/* Display microseconds value in display.
 * For 1000-2000us, the hundreds and tens are shown (ex.: 1536 us -> 53)
 * Outside of this range, also shows hundreds and tens :) but additionally in
 * main() some blinking is done to indicate "out of normal range"
 */
static void disp_dv(uint8_t which, uint16_t dv) {
	disp_num(which, (dv % 1000) / 10);
}

void main() {
	DDRB |= (1 << SHIFT_DS) | (1 << SHIFT_SH) | (1 << SHIFT_ST);
	ADMUX = (1 << REFS0); /* AVcc */
	ADCSRA = (1 << ADEN);

	DDRB |= (1 << PB1) | (1 << PB2);
	/* Setup timer: ICR is TOP for CTC mode, 20ms */
	ICR1 = 20000;
	OCR1A = 0;
	OCR1B = 0;
	TCCR1A = (1 << COM1A0) | (1 << COM1B0);
	TCCR1B = (1 << WGM13) | (1 << WGM12) | (1 << CS11);
	TIMSK1 |= (1 << OCIE1A) | (1 << OCIE1B);
	sei();

	uint16_t blink_ctr = 0;

	while (1) {
		/* read pot 1 */
		ADMUX = (1 << REFS0) | (1 << MUX0);
		_delay_us(10);
		ADCSRA |= (1 << ADSC);
		while (ADCSRA & (1 << ADSC)) { }
		uint16_t av1 = ADC;

		/* read pot 2 */
		ADMUX = (1 << REFS0) | (0 << MUX0);
		_delay_us(10);
		ADCSRA |= (1 << ADSC);
		while (ADCSRA & (1 << ADSC)) { }
		uint16_t av2 = ADC;


		uint16_t dv1 = adc2us(av1);
		uint16_t dv2 = adc2us(av2);
		duty1 = dv1;
		duty2 = dv2;

		blink_ctr++;

		if (blink_ctr & (1 << 10)) {
			disp_num(0, dv1 / 100);
			disp_num(1, dv2 / 100);
			seg7data[1] |= Dp2;
			seg7data[3] |= Dp2;
		} else {
			disp_dv(0, dv1);
			disp_dv(1, dv2);
			if (blink_ctr & (1 << 7)) {
				if ((dv1 < 1000) || (dv1 >= 2000)) {
					seg7data[0] = 0;
					seg7data[1] = 0;
				}
				if ((dv2 < 1000) || (dv2 >= 2000)) {
					seg7data[2] = 0;
					seg7data[3] = 0;
				}
			}
		}
		shiftreg_set32();

		_delay_us(1000);
		/* display dimming to prevent it from heating up too much (disabled for now) */
		if (0) for (int x = 0; x < 10; x++) {
			shiftreg_zero32();
			_delay_us(2500-700);
			shiftreg_set32();
			_delay_us(700);
		}
	}
}