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#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <util/delay.h>
#include <stdlib.h>
#include "font2.h"
#define SHUTDOWN_THRESHOLD 2048
volatile uint8_t disp[8];
int main (void)
{
uint16_t want_shutdown = 0;
// disable ADC to save power
PRR |= _BV(PRADC);
// dito
wdt_disable();
// Ports B and D drive the dot matrix display -> set all as output
DDRB = 0xff;
DDRD = 0xff;
PORTB = 0;
PORTD = 0;
// Enable pull-ups on PC3 and PC7 (button pins)
PORTC |= _BV(PC3) | _BV(PC7);
// Enable 8bit counter with prescaler=8 (-> timer frequency = 1MHz)
TCCR0A = _BV(CS01);
// raise timer interrupt on counter overflow (-> interrupt frequency = ~4kHz)
TIMSK0 = _BV(TOIE0);
disp[0] = font[0][1];
disp[1] = font[0][2];
disp[2] = font[0][3];
disp[3] = font[0][4];
disp[4] = font[0][5];
disp[5] = font[0][6];
disp[6] = font[0][7];
disp[7] = font[0][8];
#if 0
// smile!
disp[0] = 0x08;
disp[1] = 0x04;
disp[2] = 0x62;
disp[3] = 0x02;
disp[4] = 0x02;
disp[5] = 0x62;
disp[6] = 0x04;
disp[7] = 0x08;
disp[8] = 0x00;
disp[9] = 0x00;
disp[10] = 0x00;
disp[11] = 0x00;
disp[12] = 0x00;
disp[13] = 0x00;
disp[14] = 0x00;
disp[15] = 0x00;
disp[16] = 0x28;
disp[17] = 0x44;
disp[18] = 0x22;
disp[19] = 0x02;
disp[20] = 0x02;
disp[21] = 0x22;
disp[22] = 0x44;
disp[23] = 0x28;
disp[24] = 0x00;
disp[25] = 0x00;
disp[26] = 0x00;
disp[27] = 0x00;
disp[28] = 0x00;
disp[29] = 0x00;
disp[30] = 0x00;
disp[31] = 0x00;
#endif
sei();
while (1) {
// nothing to do here, go to idle to save power
SMCR = _BV(SE);
asm("sleep");
// both buttons are pressed
if ((PINC & (_BV(PC3) | _BV(PC7))) == 0) {
// naptime!
// But not before both buttons have been pressed for
// SHUTDOWN_THRESHOLD * 0.256 ms. And then, not before both have
// been released, because otherwise we'd go te sleep when
// they're pressed and wake up when they're released, which
// isn't really the point here.
if (want_shutdown < SHUTDOWN_THRESHOLD) {
want_shutdown++;
}
// TODO turn off display when want_shutdown >= SHUTDOWN_THRESHOLD
// to indicate we're about to shut down
} // both buttons released
else if ((PINC & _BV(PC3)) && (PINC & _BV(PC7))) {
if (want_shutdown >= SHUTDOWN_THRESHOLD) {
// actual naptime
// turn off display
PORTB = 0;
PORTD = 0;
// enable PCINT on PC3 (PCINT11) and PC7 (PCINT15) for wakeup
PCMSK1 |= _BV(PCINT15) | _BV(PCINT11);
PCICR |= _BV(PCIE1);
// go to power-down mode
SMCR = _BV(SM1) | _BV(SE);
asm("sleep");
// execution will resume here - disable PCINT again.
// Don't disable PCICR, something else might need it.
PCMSK1 &= ~(_BV(PCINT15) | _BV(PCINT11));
PCICR &= ~_BV(PCIE1);
}
want_shutdown = 0;
}
}
return 0;
}
/*
* 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 display[8];
uint8_t i;
if (++scroll == 512) {
scroll = 0;
if (++disp_offset == sizeof(disp)) {
disp_offset = 0;
}
for (i = 0; i < 8; i++) {
display[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 = display[active_col];
PORTB = _BV(active_col);
if (++active_col == 8)
active_col = 0;
}
ISR(PCINT1_vect)
{
// we use PCINT1 for wakeup, so we should catch it here (and do nothing)
}
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