diff options
| -rw-r--r-- | main.c | 58 |
1 files changed, 46 insertions, 12 deletions
@@ -1,24 +1,32 @@ #include <avr/io.h> #include <avr/interrupt.h> +#include <avr/power.h> #include <avr/sleep.h> #include <avr/wdt.h> #include <util/delay.h> #include <stdlib.h> -volatile uint8_t disp[16]; +volatile uint8_t disp[32]; int main (void) { + // disable ADC to save power + power_adc_disable(); + + // dito wdt_disable(); + // Ports B and D drive the dot matrix display -> set all as output DDRB = 0xff; DDRD = 0xff; PORTB = 0; PORTD = 0; - TCCR0A = _BV(CS00); // no prescaler (/8 without software prescaler is okay too) - TIMSK0 = _BV(TOIE0); // interrupt on overflow + // Enable 8bit counter with prescaler=8 (-> timer frequency = 1MHz) + TCCR0A = _BV(CS01); + // raise timer interrupt on counter overflow (-> interrupt frequency = ~4kHz) + TIMSK0 = _BV(TOIE0); // smile! disp[0] = 0x08; @@ -29,24 +37,50 @@ int main (void) disp[5] = 0x62; disp[6] = 0x04; disp[7] = 0x08; - disp[8] = 0x28; - disp[9] = 0x44; - disp[10] = 0x22; - disp[11] = 0x02; - disp[12] = 0x02; - disp[13] = 0x22; - disp[14] = 0x44; - disp[15] = 0x28; + 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; sei(); while (1) { + // nothing to do here, go to sleep to save power sleep_enable(); + sleep_cpu(); } 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; @@ -55,7 +89,7 @@ ISR(TIMER0_OVF_vect) uint8_t buffer_col; - if (++scroll == 1024) { + if (++scroll == 256) { scroll = 0; if (++disp_offset == sizeof(disp)) { disp_offset = 0; |