[time-nuts] 1PPS to 32.768 khz

Hal Murray hmurray at megapathdsl.net
Wed Oct 19 06:29:09 EDT 2016

davidwhess at gmail.com said:
> I think a PIC might be fast enough to DDS it.  The output bandpass filter
> will cure a lot of sin.  Using a dedicated switched capacitor filter would
> be fun but more expensive. 

There are two parts to a DDS like setup.  One is the math for the DDS and 
then spining for the right number of cycles.  The other is a PLL to measure 
the speed of the clock driving the CPU and tweaking the DDS "constants" so it 
tracks the PPS.  It might be fun to do that with a fixed number of cycles.  
Or maybe you can use a counter/timer to count cycles.

You don't need any filtering.  The goal is not to make a pretty picture on a 
spectrum analyzer.  All you have to do is get the long term timing right so 
the clock doesn't drift.

These are my opinions.  I hate spam.

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