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#include <avr/interrupt.h>
#include <avr/io.h>
#include <stdint.h>
#include <util/delay.h>
#include "display.h"
#include "rtc.h"
void display_setup() {
// Set prescaler CS01 + CS00 (F_CPU / 64) + CTC
// For 32768Hz -> 32768/64 = 512Hz
TCCR0B = (1 << CS01) | (1 << CS00) | (1 << WGM02);
TCCR0A = (1 << WGM01) | (1 << WGM00);
TCNT0 = 0; // Start counting from 0
OCR0A = 1; // 0-1 = 2 counts before timer interrupt (512/2 = 256Hz)
OCR0B = 0;
TIFR0 = (1 << OCF0A) | (1 << OCF0B) | (1 << TOV0); // Clear interrupt flags
TIMSK0 = (1 << OCIE0A); // Enable timer overflow interrupt
// Draw startup state
DDRA |= 0b11111111;
DDRB |= 0b11111111;
PORTA = (1 << PA7);
PORTB = (1 << PB2);
}
volatile uint8_t current_digit = 0;
// Render current digit
void display_render(void) {
write_time(current_digit);
// Cycle through the 4 digits
current_digit = (current_digit + 1) % 4;
}
// Special segments index position
#define SPECIAL_SEGMENT_1 5
#define SPECIAL_SEGMENT_2 6
// Special segment masked pins
#define SPECIAL_SEGMENT_MASK_1 ((1 << 5) | (1 << 10))
#define SPECIAL_SEGMENT_MASK_2 ((1 << 6) | (1 << 7))
// All special segment pings
#define SPECIAL_SEGMENT_PINS (SPECIAL_SEGMENT_MASK_1 | SPECIAL_SEGMENT_MASK_2)
// Digit position -> special segment pin
static uint8_t special_segment_pins[] = {5, 10, 6, 7};
// Digit position -> special segment anti-pin (pair of pin)
static uint8_t special_segment_antipins[] = {10, 5, 7, 6};
void write_time(uint8_t digit_index) {
// reset pins
uint16_t ddr = ~SPECIAL_SEGMENT_PINS;
uint16_t port = 0;
uint8_t digits[] = {seconds_digit1, seconds_digit2, minutes_digit1,
minutes_digit2};
uint8_t digit = digits[digit_index];
uint16_t segments = digit_masks[digit];
uint8_t pin = special_segment_pins[digit_index];
uint8_t antipin = special_segment_antipins[digit_index];
uint8_t segment_pin =
digit_index / 2 == 0 ? SPECIAL_SEGMENT_1 : SPECIAL_SEGMENT_2;
uint8_t other_segment_pin =
digit_index / 2 == 0 ? SPECIAL_SEGMENT_2 : SPECIAL_SEGMENT_1;
uint16_t other_segment_mask =
digit_index / 2 == 0 ? SPECIAL_SEGMENT_MASK_2 : SPECIAL_SEGMENT_MASK_1;
// Activate special segment
ddr |= (1 << pin);
port = segments | (1 << pin);
if (segments & (1 << segment_pin)) {
// If seg inactive, enable other input and enable pull up res
ddr &= ~(1 << antipin);
port |= (1 << antipin);
} else {
// If seg active, enable other output and set to 0
ddr |= (1 << antipin);
port &= ~(1 << antipin);
}
// Activate other special segment
if ((segments & (1 << other_segment_pin)) == 0) {
ddr |= other_segment_mask;
port &= ~other_segment_mask;
}
DDRA = ddr;
DDRB = ddr >> 8;
PORTA = port;
PORTB = port >> 8;
}
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