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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"
#include "font.h"
Display display;
Display::Display()
{
disp_buf[0] = 0xff;
disp_buf[1] = 0xfb;
disp_buf[2] = 0xdd;
disp_buf[3] = 0xfd;
disp_buf[4] = 0xdd;
disp_buf[5] = 0xfb;
disp_buf[6] = 0xff;
disp_buf[7] = 0xff;
char_pos = -1;
}
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);
}
void Display::multiplex()
{
static uint16_t scroll;
uint8_t i, glyph_len;
uint8_t *glyph_addr;
/*
* 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;
if (++scroll == 512) {
scroll = 0;
for (i = 0; i < 7; i++) {
disp_buf[i] = disp_buf[i+1];
}
glyph_addr = (uint8_t *)pgm_read_ptr(&font[(uint8_t)display.string[str_pos]]);
glyph_len = pgm_read_byte(&glyph_addr[0]);
char_pos++;
if (char_pos > glyph_len) {
char_pos = 0;
str_pos++;
}
if (display.string[str_pos] == 0) {
str_pos = 0;
}
if (char_pos == 0) {
disp_buf[7] = 0xff; // whitespace
} else {
disp_buf[7] = ~pgm_read_byte(&glyph_addr[char_pos]);
}
}
}
void Display::reset()
{
for (int i = 0; i < 8; i++)
disp_buf[i] = 0xff;
str_pos = 0;
char_pos = -1;
}
/*
* 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)
{
display.multiplex();
}
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