Re: [time-nuts] CSAC Project(was CSAC purchase)
Bob:
That makes sense, since you need some display short of the
included software. Might end up giany cell phone size?
Beyond my abilities, since I am a software guy, not hardware.
Ronald
Hi
One way or the other you will need some “smarts” to do aging compensation.
That implies adding a CPU of some sort to the “system” you are building. There
is no built in subsystem on the CSAC that will do any of this for you. You also
need some sort of display for your “wrist watch”. Having the CPU handle that
at the same time makes a lot of sense.
Bob
Hi
“Included software” on the CSAC is a pretty short list …. There
is not much past the “stuff” to set it on frequency and read out
a few alarms.
One thing that gets into a lot of these projects:
We are Time Nuts and spec things in terms of time. This error
over that period is some specific number. Maybe we look at
temperature rather than sit it on the shelf for a year. The number
is still a time error.
Pretty much everybody making devices spec’s them (and may think
of them) as frequency generating gizmos. They all spec a frequency
error over some condition (like a period of time). Unfortunately time
error and frequency error aren’t the same thing.
This also gets into things like control loops. Generally the input is a
time error and the output is a frequency control. Same basic gotcha
the input isn’t the same as the output. Fortunately they are related
very closely to each other.
Bob
On Jan 27, 2018, at 10:32 AM, Ronald Held ronaldheld@gmail.com wrote:
Bob:
That makes sense, since you need some display short of the
included software. Might end up giany cell phone size?
Beyond my abilities, since I am a software guy, not hardware.
Ronald
Hi
One way or the other you will need some “smarts” to do aging compensation.
That implies adding a CPU of some sort to the “system” you are building. There
is no built in subsystem on the CSAC that will do any of this for you. You also
need some sort of display for your “wrist watch”. Having the CPU handle that
at the same time makes a lot of sense.
Bob
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On 1/27/18 8:10 AM, Bob kb8tq wrote:
Hi
“Included software” on the CSAC is a pretty short list …. There
is not much past the “stuff” to set it on frequency and read out
a few alarms.
There's a half dozen serial ascii commands to the CSAC, and a
corresponding number of output messages. None are particularly "special"
- I can't imagine needing a "display" for the telemetry, except perhaps
as a novelty.
You'd want to periodically check the heater power, maybe?
I'd just expose a "diagnostic interface" on a CSAC based clock, and if
you want to fool with it (or change the frequency, etc.), you hook up
your external whatever.
LE Bluetooth Serial port perhaps?
You could write an App for a phone to talk to it, and I'm sure it will
be in the top10 on the iStore and GooglePlay within weeks. Your
retirement funding is assured. <grin>
One thing that gets into a lot of these projects:
We are Time Nuts and spec things in terms of time. This error
over that period is some specific number. Maybe we look at
temperature rather than sit it on the shelf for a year. The number
is still a time error.
Very much so. Even here on "time-nuts" we discuss more about "frequency"
- ADEV is a frequency error measure, after all.
Bob:
Interesting but too general for me. Has anyone used a CPU to read
the CSAC outputs for time/date, and for improving frequency stability?
Ronald
Hi
“Included software” on the CSAC is a pretty short list …. There
is not much past the “stuff” to set it on frequency and read out
a few alarms.
One thing that gets into a lot of these projects:
We are Time Nuts and spec things in terms of time. This error
over that period is some specific number. Maybe we look at
temperature rather than sit it on the shelf for a year. The number
is still a time error.
Pretty much everybody making devices spec’s them (and may think
of them) as frequency generating gizmos. They all spec a frequency
error over some condition (like a period of time). Unfortunately time
error and frequency error aren’t the same thing.
This also gets into things like control loops. Generally the input is a
time error and the output is a frequency control. Same basic gotcha
the input isn’t the same as the output. Fortunately they are related
very closely to each other.
Bob
Hi
Yes, I have set up a CPU to dump all the data from a CSAC. Everything
they list in their data sheet can easily be dumped via a standard UART
interface. The serial protocol works exactly the way they describe.
There is no “built in clock” so no ability to dump the time and date. You
can “improve” the frequency stability by sending whatever you want to the
tuning word. What you send and when you send it is entirely up to you.
The real issue is having something more accurate than the CSAC to
compare to when you do the frequency correction.
Bob
On Jan 27, 2018, at 7:29 PM, Ronald Held ronaldheld@gmail.com wrote:
Bob:
Interesting but too general for me. Has anyone used a CPU to read
the CSAC outputs for time/date, and for improving frequency stability?
Ronald
Hi
“Included software” on the CSAC is a pretty short list …. There
is not much past the “stuff” to set it on frequency and read out
a few alarms.
One thing that gets into a lot of these projects:
We are Time Nuts and spec things in terms of time. This error
over that period is some specific number. Maybe we look at
temperature rather than sit it on the shelf for a year. The number
is still a time error.
Pretty much everybody making devices spec’s them (and may think
of them) as frequency generating gizmos. They all spec a frequency
error over some condition (like a period of time). Unfortunately time
error and frequency error aren’t the same thing.
This also gets into things like control loops. Generally the input is a
time error and the output is a frequency control. Same basic gotcha
the input isn’t the same as the output. Fortunately they are related
very closely to each other.
Bob
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and follow the instructions there.
Jim:
Hmm, I was kit thinking that way. How rich could I get writing
an app that is only used for CSACs? Seems a small market ,IMO.
Monitoring sounds easier thenSW to drive a display.
Ronald
There's a half dozen serial ascii commands to the CSAC, and a
corresponding number of output messages. None are particularly "special"
- I can't imagine needing a "display" for the telemetry, except perhaps
as a novelty.
You'd want to periodically check the heater power, maybe?
I'd just expose a "diagnostic interface" on a CSAC based clock, and if
you want to fool with it (or change the frequency, etc.), you hook up
your external whatever.
LE Bluetooth Serial port perhaps?
You could write an App for a phone to talk to it, and I'm sure it will
be in the top10 on the iStore and GooglePlay within weeks. Your
retirement funding is assured. <grin>
Mark:
Sounds like a good idea. I have none,but some Time-nuts have more
than one. Maybe one will loan one out?
Ronald
Bob:
Now there is a snproblem, as I own nothing more accurate the data
dumping may prove usefulssni learn more.
Ronald
Hi
Yes, I have set up a CPU to dump all the data from a CSAC. Everything
they list in their data sheet can easily be dumped via a standard UART
interface. The serial protocol works exactly the way they describe.
There is no “built in clock” so no ability to dump the time and date. You
can “improve” the frequency stability by sending whatever you want to the
tuning word. What you send and when you send it is entirely up to you.
The real issue is having something more accurate than the CSAC to
compare to when you do the frequency correction.
Bob
Hi
A GPS PPS output will (most likely) be more accurate than the CSAC
each time you go back to dock with the charger. A GPS module to do
everything you would ever want to do is a sub $100 sort of item. You
would still need a bit of hardware to “glue” things together (but not a lot)
and some code running on the MCU of your choice to supervise the process.
Accuracy wise, a GPS PPS is very hard to beat.
Bob
On Jan 28, 2018, at 6:19 PM, Ronald Held ronaldheld@gmail.com wrote:
Jim:
Hmm, I was kit thinking that way. How rich could I get writing
an app that is only used for CSACs? Seems a small market ,IMO.
Monitoring sounds easier thenSW to drive a display.
Ronald
There's a half dozen serial ascii commands to the CSAC, and a
corresponding number of output messages. None are particularly "special"
- I can't imagine needing a "display" for the telemetry, except perhaps
as a novelty.
You'd want to periodically check the heater power, maybe?
I'd just expose a "diagnostic interface" on a CSAC based clock, and if
you want to fool with it (or change the frequency, etc.), you hook up
your external whatever.
LE Bluetooth Serial port perhaps?
You could write an App for a phone to talk to it, and I'm sure it will
be in the top10 on the iStore and GooglePlay within weeks. Your
retirement funding is assured. <grin>
Mark:
Sounds like a good idea. I have none,but some Time-nuts have more
than one. Maybe one will loan one out?
Ronald
Bob:
Now there is a snproblem, as I own nothing more accurate the data
dumping may prove usefulssni learn more.
Ronald
Hi
Yes, I have set up a CPU to dump all the data from a CSAC. Everything
they list in their data sheet can easily be dumped via a standard UART
interface. The serial protocol works exactly the way they describe.
There is no “built in clock” so no ability to dump the time and date. You
can “improve” the frequency stability by sending whatever you want to the
tuning word. What you send and when you send it is entirely up to you.
The real issue is having something more accurate than the CSAC to
compare to when you do the frequency correction.
Bob
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and follow the instructions there.
Bob:
Right now I own nothing that outputs a GPS PPS. GPS watches I own do
not have that option. Maybe for infrequent resets, an independent
GPS unit is better from a design and construction POV?
Ronald
Hi
A GPS PPS output will (most likely) be more accurate than the CSAC
each time you go back to dock with the charger. A GPS module to do
everything you would ever want to do is a sub $100 sort of item. You
would still need a bit of hardware to “glue” things together (but not a lot)
and some code running on the MCU of your choice to supervise the process.
Accuracy wise, a GPS PPS is very hard to beat.
Bob
Hi
As mentioned multiple times in the archives. As you get into the single digit
milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off
and one that is 1 ms off are both “good enough” if you are looking at it with a
normal eyeball.
From a design standpoint 1 ms / day / week is way different that 1 ns over the
same sort of period. Design constraints do make a big difference. It’s important
in any project to get them sorted early.
If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t
going to even get into the roundoff error. You will need the GPS gizmo to
keep the CSAC calibrated. It is only a question of how often the beast gets
used.
Bob
On Jan 28, 2018, at 7:45 PM, Ronald Held ronaldheld@gmail.com wrote:
Bob:
Right now I own nothing that outputs a GPS PPS. GPS watches I own do
not have that option. Maybe for infrequent resets, an independent
GPS unit is better from a design and construction POV?
Ronald
Hi
A GPS PPS output will (most likely) be more accurate than the CSAC
each time you go back to dock with the charger. A GPS module to do
everything you would ever want to do is a sub $100 sort of item. You
would still need a bit of hardware to “glue” things together (but not a lot)
and some code running on the MCU of your choice to supervise the process.
Accuracy wise, a GPS PPS is very hard to beat.
Bob
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.