Real-Time Clock
ISL1208 Real-Time Clock
Once progress began on the wireless, we shifted focus to the core of any alarm clock, the clock mechanism itself. We ended up choosing the Intersil ISL1208 Real-Time Clock. This chip is addressable over I2C, can store an alarm, and raise an external interrupt when the alarm is triggered. This RTC could also use a super capacitor as a backup source, using only 1.2uA in a low power mode. In this mode the clock can continue counting and maintain accurate time and alarm values for up to 30 days, when the rest of the device is unpowered.