This instructable show how to use an ATtiny85 to create a tiny watch core that can run over 1 year before recharge or replace battery.
The instruction to make the watch case may be in next instructable.
I have made a few Arduino watch before, but I found the watch using ATmega boards or ATmega chips are a little bit too big to wear. So I would like to make it with a smaller chips.
I have choose ATtiny85 just because I can easy to get one.
The challenges for using ATtiny85 are:
- It only have 8K flash memory
- It only have 5 IO pins (I would like to keep the 6th IO pin as reset for easy re-programming)
- Since the above 2 limitations, it is hard to find a complete source code for an ATtiny watch on the web
I design to develop a tailor-make code to complete these challenge, it include:
- Power control to make the watch can run over 1 year
- Revise a time library to utilize WDT for power saving purpose
- Trim down a display library to meet 8K binary limitation
- Customizable font type
- Basic UI for adjust time just like a normal digit watch