Chronodot alarm programming

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sjn3
 
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Chronodot alarm programming

Post by sjn3 »

Has anyone had any successes programming the Chronodot's (http://www.adafruit.com/products/255) alarm registers?

I'd like to try using one to power up an Uno (via a latching circuit) which would grab measurements, perform tasks, and then shut itself down (saving lots of battery power) until re-powered by the 'dot. Thanks!

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Re: Chronodot alarm programming

Post by adafruit_support_rick »

The chronodot documentation is here.
http://docs.macetech.com/doku.php/chronodot_v2.0
I don't know anything about an alarm register. Are you sure you're not confusingthe square-wave output with a programmable alarm?

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sjn3
 
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Re: Chronodot alarm programming

Post by sjn3 »

No, I don't believe I'm confused. According to the chip's PDF (http://datasheets.maxim-ic.com/en/ds/DS3231.pdf), page 12, you can have alarms trigger on date/hour/minute/second, or day-of-week/hour/minute, or repeat triggering every n'th second or n'th minute or n'th hour..etc. Pretty powerful for someone who wants to build a long-term or infrequent timing application. The output is an open-drain pin which, logically, SHOULD be able to work off of the battery, but their register setup makes it plain that the chip must be powered to handle the alarm functions. Still it's not so bad drawing 200-300µa for this instead of the Uno being constantly on and sucking down several hundred milliamps (plus the other components' draw) while doing nothing in between events.

I've started fiddling with it, trying to work through the various registers, and wondered if anyone has had success doing it. And NOW I see another posting in one of the other forums (http://forums.adafruit.com/viewtopic.php?f=22&t=43382) about alarm programming on a Chornodot [sic].

I guess all searches-before-posting ought to include reasonable misspellings...? :lol:

Thanks for the reply.

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Re: Chronodot alarm programming

Post by adafruit_support_rick »

Well, ya learn something new every day. I didn't know about that. Thanks!

It's pretty easy to set up the CPU to sleep pending an external interrupt. Is the battery backup on the Chronodot enough, or do you need to keep external power applied?

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sjn3
 
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Re: Chronodot alarm programming

Post by sjn3 »

And you've just told ME something new - I didn't think you could sleep the CPU and now I've got something else to learn.

Again, the chip's docs seem to imply that the chip HAS to be powered to do it - the battery runs the oscillator, freq stabilization, and the counter but I can t see why it couldn't toggle one single FET for a fraction of a second too...

Further experimentation will tell.

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Re: Chronodot alarm programming

Post by adafruit_support_rick »

See the Arduino Playground page on Sleep. Check out the "Level Interrupt" section re: using an external interrupt to wake.

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