Encoded 1PPS signals
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS input
for calibration purposes. However I would like to be able to provide more
time information than just the second pulses. It occurs to me that full time
info could be encoded onto a 1PPS stream by changing the width of the pulse
itself. The rising edge can be left unchanged to indicate the precise
second, but the trailing edge can vary between (say) 100mSec and 300mSec,
and this could encode 60 bits (with suitable idle pulses etc for
synchronisation) in each minute. Using this I could encode full date and
time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone developed
something along this line?
If no, I plan to implement something suitable myself, and will publish it
should it be useful to others.
Regards
Clayton
(VK1TKA)
Yes, already done: the DCF77 VLF time transmitter and others.
On Tue, Jun 26, 2012 at 3:15 PM, Clayton G clayton@isnotcrazy.com wrote:
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS
input for calibration purposes. However I would like to be able to provide
more time information than just the second pulses. It occurs to me that
full time info could be encoded onto a 1PPS stream by changing the width of
the pulse itself. The rising edge can be left unchanged to indicate the
precise second, but the trailing edge can vary between (say) 100mSec and
300mSec, and this could encode 60 bits (with suitable idle pulses etc for
synchronisation) in each minute. Using this I could encode full date and
time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone
developed something along this line?
If no, I plan to implement something suitable myself, and will publish it
should it be useful to others.
Regards
Clayton
(VK1TKA)
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On 6/26/2012 9:15 AM, Clayton G wrote:
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS
input for calibration purposes. However I would like to be able to
provide more time information than just the second pulses. It occurs
to me that full time info could be encoded onto a 1PPS stream by
changing the width of the pulse itself. The rising edge can be left
unchanged to indicate the precise second, but the trailing edge can
vary between (say) 100mSec and 300mSec, and this could encode 60 bits
(with suitable idle pulses etc for synchronisation) in each minute.
Using this I could encode full date and time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone
developed something along this line?
If no, I plan to implement something suitable myself, and will publish
it should it be useful to others.
Regards
Clayton
(VK1TKA)
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and follow the instructions there.
I think you describe modifying IRIG. Just a thought
Regards
Paul.
Hi Clayton:
Check out WWVB.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
Clayton G wrote:
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS input for calibration purposes. However I would
like to be able to provide more time information than just the second pulses. It occurs to me that full time info
could be encoded onto a 1PPS stream by changing the width of the pulse itself. The rising edge can be left unchanged
to indicate the precise second, but the trailing edge can vary between (say) 100mSec and 300mSec, and this could
encode 60 bits (with suitable idle pulses etc for synchronisation) in each minute. Using this I could encode full date
and time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone developed something along this line?
If no, I plan to implement something suitable myself, and will publish it should it be useful to others.
Regards
Clayton
(VK1TKA)
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.
Hi
I suspect that encoding 10 bits via AM PWM is likely to be a bit exciting
from a signal to noise standpoint on the receiving end. Back in the good old
days a 1/3 2/3 width switch was a normal way to encode a single bit.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Clayton G
Sent: Tuesday, June 26, 2012 9:16 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Encoded 1PPS signals
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS input
for calibration purposes. However I would like to be able to provide more
time information than just the second pulses. It occurs to me that full time
info could be encoded onto a 1PPS stream by changing the width of the pulse
itself. The rising edge can be left unchanged to indicate the precise
second, but the trailing edge can vary between (say) 100mSec and 300mSec,
and this could encode 60 bits (with suitable idle pulses etc for
synchronisation) in each minute. Using this I could encode full date and
time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone developed
something along this line?
If no, I plan to implement something suitable myself, and will publish it
should it be useful to others.
Regards
Clayton
(VK1TKA)
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.
Am 26.06.2012 18:12, schrieb Bob Camp:
fo could be encoded onto a 1PPS stream by changing the width of the pulse
itself. The rising edge can be left unchanged to indicate the precise
second, but the trailing edge can vary between (say) 100mSec and 300mSec,
and this could encode 60 bits (with suitable idle pulses etc for
synchronisation) in each minute. Using this I could encode full date and
time into the 1PPS stream.
My question is, does such a standard already exist, or has anyone developed
something along this line?
If no, I plan to implement something suitable myself, and will publish it
should it be useful to others.
You could recycle the DCF77 format:
http://www.ptb.de/cms/en/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77.html
There seem to be decoders for it on the net.
regards, Gerhard
On Tue, Jun 26, 2012 at 6:15 AM, Clayton G clayton@isnotcrazy.com wrote:
Hi Nuts,
I have been building an LF transmitter, and have provision for a 1PPS
input for calibration purposes. However I would like to be able to provide
more time information than just the second pulses. It occurs to me that
full time info could be encoded onto a 1PPS stream by changing the width of
the pulse itself. The rising edge can be left unchanged to indicate the
precise second, but the trailing edge can vary between (say) 100mSec and
300mSec, and this could encode 60 bits (with suitable idle pulses etc for
synchronisation) in each minute. Using this I could encode full date and
time into the 1PPS stream.
There are a few better ways to do this. The general term is "time code".
IRIG is one common time code and there are others, such as that used by
WWVB. It is not hard to create a good time code stream. If you look at
the source code distribution for NTP in the "test" directory there is a C
source code for a time code generator (the one used by WWVB) and it will
output the signal using an audio interface. Assuming you have the PPS
signal going to a Linux or BSD based computer the time code can be accurate
at the "handful of microseconds" level
The other point is "why?" You do not need to encode anything on top of
the PPS. Here is a very simple example: If you run a local oscillator at
even (say) 1kHz and keep it phase locked to the incoming PPS you now have a
digital millisecond counter that is tied to the PPS. If you run a 1Mhz
oscillator you have a microsecond counter. No need at all to encode time
on the PPS signal you get that from the local counter. It is not hard
at all to keep this accurate at the "few uSec level."
In simpler terms, the PPS leading edge already gives you sub uSec time
because you can run a fast-ticking clock and count the ticks after the
leading edge of the PPS. Also at the same time you count ticks from
leading edge to leading edge and adjust your local "ticker" to keep it at
the correct rate.
Chris Albertson
Redondo Beach, California