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#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <util/delay.h>
#include <stdlib.h>
#include "display.h"
Display display;
extern volatile uint8_t disp[8];
void Display::disable()
{
TIMSK0 &= ~_BV(TOIE0);
PORTB = 0;
PORTD = 0;
}
void Display::enable()
{
// Ports B and D drive the dot matrix display -> set all as output
DDRB = 0xff;
DDRD = 0xff;
// Enable 8bit counter with prescaler=8 (-> timer frequency = 1MHz)
TCCR0A = _BV(CS01);
// raise timer interrupt on counter overflow (-> interrupt frequency = ~4kHz)
TIMSK0 = _BV(TOIE0);
}
/*
* Draws a single display column. This function should be called at least once
* per millisecond.
*
* Current configuration:
* Called every 256 microseconds. The whole display is refreshed every 2048us,
* giving a refresh rate of ~500Hz
*/
ISR(TIMER0_OVF_vect)
{
static uint8_t active_col = 0;
static uint16_t scroll = 0;
static uint8_t disp_offset = 0;
static uint8_t disp_buf[8];
uint8_t i;
if (++scroll == 512) {
scroll = 0;
if (++disp_offset == sizeof(disp)) {
disp_offset = 0;
}
for (i = 0; i < 8; i++) {
disp_buf[i] = ~disp[(disp_offset + i) % sizeof(disp)];
}
}
/*
* To avoid flickering, do not put any code (or expensive index
* calculations) between the following three lines.
*/
PORTB = 0;
PORTD = disp_buf[active_col];
PORTB = _BV(active_col);
if (++active_col == 8)
active_col = 0;
}
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