[time-nuts] GPSDO Alternatives

Lizeth Norman normanlizeth at gmail.com
Thu Dec 6 23:34:17 UTC 2012


Bob et al:
Have been following this thread with interest.
Re the input capture versus interrupt, I do believe (at least the 2560
does this) that you can do both. It's been a while since I looked. a
look at the hardware manual. Was interested in this feature to do
hardware timing.
Norm

On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp <lists at rtty.us> wrote:
> Hi
>
> That would be an input capture rather than an interrupt.
>
> Bob
>
> On Dec 6, 2012, at 6:16 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
>
>>
>> albertson.chris at gmail.com said:
>>> You'd have to seriously divide down the output from the 10MHz OCXO if you
>>> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>>> at the higher clock rate you'd still have poor resolution.
>>
>>> I image each interrupt handler would sample some internal counter and the
>>> background task would look at the delta between the two and adjust the DAC
>>> to drive the OCXO to close the difference.   The resolution would be
>>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 second
>>> period it might wrk well enough.  I can't know without doing a more detailed
>>> design
>>
>> Do some of the counter/timer modules have an option to run the counter off an
>> internal clock and copy the value into another register on an external signal?
>>
>> That avoids any interrupt latency.
>>
>>
>>
>>
>> --
>> These are my opinions.  I hate spam.
>>
>>
>>
>>
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>
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