Ignition monitor: Initial commit

Implemented:
* sleep mode
* monitoring portb pin3
* switching portb pin4

Missing:
* shutdown guard time

src/main.c

@@ -0,0 +1,42 @@
+#include <stdint.h>
+
+#define F_CPU 1000000UL
+
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <avr/sleep.h>
+#include <avr/wdt.h>
+#include <util/delay.h>
+
+#define IGNITION_PIN    4
+#define POWER_PIN       3
+
+int main(void)
+{
+    DDRB = 0xff;
+    DDRB &= ~(1 << IGNITION_PIN);
+    PORTB |= (1 << PB0) | (1 << PB1) | (1 << PB2);
+
+    wdt_enable(WDTO_8S);
+    while(1) {
+        wdt_reset();
+        if(PINB & (1 << IGNITION_PIN)) {
+            PORTB |= (1 << POWER_PIN);
+        } else {
+            if(PINB & (1 << POWER_PIN)) {
+                for(uint8_t i = 0; i < 100; ++i) {
+                    wdt_reset();
+                    _delay_ms(100);
+                }
+                PORTB &= ~(1 << POWER_PIN);
+            }
+            wdt_enable(WDTO_8S);
+            set_sleep_mode(SLEEP_MODE_PWR_DOWN);
+            sleep_enable();
+            sleep_cpu();
+            sleep_disable();
+        }
+    }
+
+    return 0;
+}