Litmer: 8 seconds watchdog with power-down sleep mode

Played with power-down sleep mode. It's very low power consumption mode, cpu is not running. Then played with watchdog timer. Set it to 8 seconds with prescaler and enabled interrupt. So every 8 seconds watchdog wakeups cpu and run interrupt. In this interrupt code I going to check rtc time and compare it with on/off times stored in eeprom and then take action.

I will probably make a battery backup for this device, so it can run on AC when available or on battery and charge battery when on AC. So lower power consumption is better. Take a look at code at:code.avrnoob.com/litmer.