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Discussion of precise time and frequency measurement

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Re: pps pulse timestamp device

HM
Hal Murray
Mon, Feb 12, 2024 4:27 AM

As others have pointed out, the TICC is a wonderful tool for your problem.
It's a lot more expensive than a Teensy but a lot cheaper than typical lab
gear with equivalent resolution.  It needs an external 10 MHz clock.  It has
much higher resolution than your ns.

I think your ns is a nasty case.  It falls in a hole between easy for a CPU
and what you get with expensive lab gear.

If you need better than a ns, the TICC is wonderful.

If you need less than a a ns, you might make do with something like a Teensy.
Are you happy writing that sort of software?  Check the data sheet and see how
fast the counters actually run.  Often the counters connected to IO pins run
slower than the CPU speed.

The TI ARM chip on the BeagleBone series of boards has a pair of
fast-but-not-smart CPUs designed for this sort of thing.  I've never used
them.  I'm pretty sure there is Linux software available for timestamping, but
a quick search didn't find any.

What are you trying to measure?  Do you want the pulse to pulse jitter or the
offset of the PPS from a GPS relative to some wonderful truth?

With a TICC, you can measure the pulse-to-pulse jitter with a stable reference
clock (crystal)  that isn't exactly 10 MHz.  (If you stand on your head, you
can turn things inside out and use a PPS from a GPS to measure the frequency
of a TICC's external clock.)

If you want to measure relative to some truth, feed a PPS from that truth into
the second channel on the TICC.

--
These are my opinions.  I hate spam.

As others have pointed out, the TICC is a wonderful tool for your problem. It's a lot more expensive than a Teensy but a lot cheaper than typical lab gear with equivalent resolution. It needs an external 10 MHz clock. It has much higher resolution than your ns. I think your ns is a nasty case. It falls in a hole between easy for a CPU and what you get with expensive lab gear. If you need better than a ns, the TICC is wonderful. If you need less than a a ns, you might make do with something like a Teensy. Are you happy writing that sort of software? Check the data sheet and see how fast the counters actually run. Often the counters connected to IO pins run slower than the CPU speed. The TI ARM chip on the BeagleBone series of boards has a pair of fast-but-not-smart CPUs designed for this sort of thing. I've never used them. I'm pretty sure there is Linux software available for timestamping, but a quick search didn't find any. What are you trying to measure? Do you want the pulse to pulse jitter or the offset of the PPS from a GPS relative to some wonderful truth? With a TICC, you can measure the pulse-to-pulse jitter with a stable reference clock (crystal) that isn't exactly 10 MHz. (If you stand on your head, you can turn things inside out and use a PPS from a GPS to measure the frequency of a TICC's external clock.) If you want to measure relative to some truth, feed a PPS from that truth into the second channel on the TICC. -- These are my opinions. I hate spam.
JS
Juan Solano
Thu, Feb 15, 2024 6:19 AM

Hal,

thanks for the advice.

I am trying to measure pulse to pulse jitter of a PPS signal that I am
generating myself on a couple of different embedded linux systems,
basically this is a learning project where I write a linux kernel
driver to produce this PPS.

I have a Teensy and some stm32 dev boards that I could use,
however I would rather get something tried and tested to timestamp,
otherwise there are too many unknowns, I will not know if/where I have
made a mistake and on which side.

The TICC seems to be a great option, just trying to convince myself
that I can justify the cost going forward :)

Cheers,
Juan.

Hal, thanks for the advice. I am trying to measure pulse to pulse jitter of a PPS signal that I am generating myself on a couple of different embedded linux systems, basically this is a learning project where I write a linux kernel driver to produce this PPS. I have a Teensy and some stm32 dev boards that I could use, however I would rather get something tried and tested to timestamp, otherwise there are too many unknowns, I will not know if/where I have made a mistake and on which side. The TICC seems to be a great option, just trying to convince myself that I can justify the cost going forward :) Cheers, Juan.
BC
Bob Camp
Thu, Feb 15, 2024 4:48 PM

Hi

If this is simply for some testing:

There are a lot of frequency counters out there that will do this sort of thing. Plug in and dump the data out the GPIB or serial port. Not much messing around.

Bob

On Feb 15, 2024, at 1:19 AM, Juan Solano via time-nuts time-nuts@lists.febo.com wrote:

Hal,

thanks for the advice.

I am trying to measure pulse to pulse jitter of a PPS signal that I am
generating myself on a couple of different embedded linux systems,
basically this is a learning project where I write a linux kernel
driver to produce this PPS.

I have a Teensy and some stm32 dev boards that I could use,
however I would rather get something tried and tested to timestamp,
otherwise there are too many unknowns, I will not know if/where I have
made a mistake and on which side.

The TICC seems to be a great option, just trying to convince myself
that I can justify the cost going forward :)

Cheers,
Juan.


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Hi If this is simply for some testing: There are a lot of frequency counters out there that will do this sort of thing. Plug in and dump the data out the GPIB or serial port. Not much messing around. Bob > On Feb 15, 2024, at 1:19 AM, Juan Solano via time-nuts <time-nuts@lists.febo.com> wrote: > > Hal, > > thanks for the advice. > > I am trying to measure pulse to pulse jitter of a PPS signal that I am > generating myself on a couple of different embedded linux systems, > basically this is a learning project where I write a linux kernel > driver to produce this PPS. > > I have a Teensy and some stm32 dev boards that I could use, > however I would rather get something tried and tested to timestamp, > otherwise there are too many unknowns, I will not know if/where I have > made a mistake and on which side. > > The TICC seems to be a great option, just trying to convince myself > that I can justify the cost going forward :) > > Cheers, > Juan. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com
EK
Erik Kaashoek
Thu, Feb 15, 2024 5:05 PM

If I was ready I could recommend this device but alas, not yet
Contains a GPSDO and two fully independent channels for frequency / time
measurements.
Battery powered with 4" display
USB connection to computer for logging measurement data and local
storage on SD card.
As pictured it is measuring time difference of two PPS inputs with 40 ps
resolution

If I was ready I could recommend this device but alas, not yet Contains a GPSDO and two fully independent channels for frequency / time measurements. Battery powered with 4" display USB connection to computer for logging measurement data and local storage on SD card. As pictured it is measuring time difference of two PPS inputs with 40 ps resolution