[time-nuts] 1PPS to 32.768 khz
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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