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I have thought a bit about this.

The least effort path is to take an existent Eta control module (the small board with the microprocessor) and work with the programming.. but I doubt the source is available.

The next path is to replace the xtal with your own TC xtal... if any watch is fed the correct pulses, no matter what happens after that, it will be HE. It is clever but has a lot less real estate for hardware as you still need a working xtal. Custom chip fab might make it as an 'end plug' ... not cheap in qty 1 but real cheap in qty 1,000,000 ;-)
 

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I have thought a bit about this.

The least effort path is to take an existent Eta control module (the small board with the microprocessor) and work with the programming.. but I doubt the source is available.
I mean.. Really, how hard can it be.o|

Given that RC watches are turning up everywhere I thought maybe rather than fighting it, it might be easier to control the source. If I had a non- portable, but very accurate time source connected to a small radio transmitter broadcasting on the same frequncies as standard time broadcasts then my watch could sync with my clock. Probably easier said than done ..

or
http://www.linuxdevices.com/articles/AT9330943155.html
http://www.linuxdevices.com/news/NS6580187845.html
 

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I mean.. Really, how hard can it be.o|
l
Reverse engineering ROMs is doable... but a real pain. I could probably borrow the equipment, but who as multiple months to devote to it??

The Linux watch is a miniature computer... that's easy in some respects.
 

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Discussion Starter #5
Ahh, but with an AB sensor, you also get temp for free and the temp always reads roughly the case temperature, so it's probably a good way to feed compensation into the regulation circuitry without using a TC crystal.

I am all for Linux but I think for this application, a simple run to completion model would work. Compared to what one does in an RTOS, none of this stuff is time-critical. Monitor sensors once or twice a second, update the display once a second. Any modern microcontroller should be able to do this.

A friend of mine recommended the TI 430 series microcontrollers with built in LCD controller.

And there is always one of these:

http://www.yeswatch.com/wrist-watch/timekeeper/tech_specs.html
 
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