Jim,
I had the intent to try this, but never got around doing it. Thanks for
reminding me. Please share any enhancements.
I did exchange some emails with Lars, but as that project never got off
the ground, it faded out.
Cheers,
Magnus
On 09/21/2015 10:02 PM, Jim Harman wrote:
Hi Can,
For a simple analog solution, you might try a 74HC4046 phase detector
followed by a diode and RC network as used in Lars Walenius' GPSDO,
described here in the archives:
https://www.febo.com/pipermail/time-nuts/2014-February/082820.html
The phase detector produces a pulse whose width equals the time difference
between the two pulses. The RC network converts this to a voltage
proportional to the time difference, which you then measure with the MCU's
A/D converter. Using the rising edge of the signal at pin 14 as the
interrupt source triggers the A/D converter at the end of the pulse, which
corresponds to the peak of the analog signal.. The 1 meg resistor
discharges the capacitor between pulses.
Lars' code also includes a filtering algorithm which does a nice job of
controlling one of the oscillators to match the 1-PPS generated by the GPS.
I have enhanced this if you are interested.
On Mon, Sep 21, 2015 at 1:45 PM, Can Altineller <[email protected]>
wrote:
I probably need a hardware to measure the time pulses more precisely. I
thought of XOR'ing the clocks, and measuring both rising and falling edges
trough interrupts, but when the pulse is close enough, it will lead to same
condition.
Are there any solutions to this problem? Maybe an analog hack? And what
are the mostly used algorithms to tune an oscillator to another? Currently
my algorithm sign corrects the result difference, and adjusts aging
register simply by adding to it, then runs a conversion command each second
to add or substract the ppms.
This looks a lot of fun,
Best Regards,
Can Altineller
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