[Icc-avr] Maxim MAX6917 alarm problem

[Paul Mateer]

Hi ...
I haven't used that chip, but on most you have to make sure you enable the
interrupt on the RTC and make sure you have the correct alarm rate plugged
into the registers.  Does the RTC actually keep time (is it actually
running)?  I had one chip where I had to short the external back-up battery
pin to ground momentaraliy before things would run.  You must also clear the
alarm interrupt on the RTC before another will occur too.

that's my 2 cents....


On 10/2/07, John Baraclough <j_baraclough at zetnet.co.uk> wrote:
>
> Hi Andy,
>
> First hang an LED on the 1Hz output to make sure the oscillator is
> running correctly. Then put an external 10k pull-up on PE4, just in
> case the internal pull-ups aren't working for some reason.
>
> All the best for now,
> John
>
> At 17:35 02/10/2007, you wrote:
> >Hi
> >
> >We're having trouble with the alarm on a MAX6917 I2C uP Supervisor/RTC
> >device.
> >
> >I2C comms to the device is working fine and we can read/write all RTC
> >registers. The ALM output of the MAX6917 is connected directly to the
> INT4
> >(PE4) input of a Mega2560 with internal pullup enabled.
> >
> >We just can't get this beast to generate an interrupt, either at a
> specific
> >time, or even once per second.
> >
> >We've tried this on three different boards and my h/w guy (who's just
> shoved
> >off on holiday) assures me that the design is good and that the boards
> are
> >not faulty.
> >
> >Any gotchas I'm missing ?  Or other suggestions ?
> >
> >TIA.
> >
> >Andy.
> >
> >--
> > >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> > >>
> > >>  Andy Syms        Technosoft Systems Ltd
> > >>
> > >>     email : asyms at technosoft.co.uk
> > >>     website : www.technosoft.co.uk
> > >>
> > >>       tel : +44 (0) 1483 799554
> > >>       fax : +44 (0) 1483 799664
> > >>
> > >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> >
> >
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-- 
Paul Mateer, AA9GG
Elan Engineering Corp.
www.elanengr.com
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