[time-nuts] PICPET- was Affordable (cheap) COTS (etc)

Tom Van Baak tvb at LeapSecond.com
Fri Jan 24 17:20:35 EST 2014


Brian,

> Well, my disciplining code is going to run as an FLL rather than
> a PLL to generate the correction for the OCXO or the Rb reference.

The Propeller should work fine for a GPSDO. AFAIK no one has done this yet and I encourage you to try. The Parallax Propeller chip gets mentioned on the list once a year. Being an old Basic Stamp and SX guy, I have a soft spot for the Propeller too.

Do you plan an external DAC or will you obtain high resolution with some sort of PWM-only solution? Maybe we should take this off-list while the Q&A is sorted out.

> Most people use a 5MHz crystal and the x16 PLL to clock the processors
> at 80MHz. I have been told that the Propeller will run at 100MHz just fine.

My plans were to use the Propeller for a multi-channel, higher-resolution, time/frequency counter. As such the ADEV when the internal 16x PLL is enabled is of some interest. Then again, I should stop worrying and just measure it.

> I just thought that, while the PLL would have a bit more jitter, having the
> extra 3 bits of resolution would be useful in accumulating the error.

Yes, I would agree.

The only issue I can see with the Propeller is that once you complete your GPSDO you'd have a thousand times more interested users world-wide if you had done it with an Arduino or RPi. I'm not saying the Propeller isn't a unique and interesting chip, it's just that in the past 5 years Arduino and RPi (and others) have completely taken over the hobbyist world. The holy grail would be a turn-key Arduino GPSDO shield. Or Rpi GPSDO/NTP server.

Anyway, let's take this off-list. If anyone else is interested, let me know too.

Thanks,
/tvb



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