Time Synchronisation on Arcnet Network

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Padraig Furlong

Time Synchronisation on Arcnet Network

Post by Padraig Furlong » Fri Nov 28, 2003 12:43 pm

Hi,
We have a number of Qnx4 PCs distributed over an arcnet network. One of the
PCs is getting its time from a GPS receiver. What is the recommended way to
distribute the time to the other Qnx4 PCs

Many thanks

Padraig

David Gibbs

Re: Time Synchronisation on Arcnet Network

Post by David Gibbs » Fri Nov 28, 2003 3:56 pm

Padraig Furlong <Padraig.Furlong@rte.ie> wrote:
Hi,
We have a number of Qnx4 PCs distributed over an arcnet network. One of the
PCs is getting its time from a GPS receiver. What is the recommended way to
distribute the time to the other Qnx4 PCs
The standard way of doing this is ntp -- but that uses TCP/IP for
communication, which isn't likely to work accross arcnet.

If sudden time jumps aren't a problem, I'd try something like:

rtc net <node_id_with_gps>

On a regular basis.

But, that will give sudden time jumps. If you can't have sudden time
jumps, I'd write a custom application that runs on a periodic basis
(timer driven, every 10 minutes? every hour? depends on how close
your time needs to be, and how quickly it drifts) that each time it
wakes up will get the local time, get the time on the GPS node, and
use qnx_adj_time() to resynch the two.

qnx_getclock() takes a pid/vc; it can be used to get the remote time.

-David
--
QNX Training Services
http://www.qnx.com/support/training/
Please followup in this newsgroup if you have further questions.

Padraig Furlong

Re: Time Synchronisation on Arcnet Network

Post by Padraig Furlong » Fri Nov 28, 2003 4:45 pm

David,
I thought that I might require some custom software.
Many thanks for your ideas

Padraig
"David Gibbs" <dagibbs@qnx.com> wrote in message
news:bq7r6h$jcs$1@nntp.qnx.com...
Padraig Furlong <Padraig.Furlong@rte.ie> wrote:
Hi,
We have a number of Qnx4 PCs distributed over an arcnet network. One of
the
PCs is getting its time from a GPS receiver. What is the recommended way
to
distribute the time to the other Qnx4 PCs

The standard way of doing this is ntp -- but that uses TCP/IP for
communication, which isn't likely to work accross arcnet.

If sudden time jumps aren't a problem, I'd try something like:

rtc net <node_id_with_gps

On a regular basis.

But, that will give sudden time jumps. If you can't have sudden time
jumps, I'd write a custom application that runs on a periodic basis
(timer driven, every 10 minutes? every hour? depends on how close
your time needs to be, and how quickly it drifts) that each time it
wakes up will get the local time, get the time on the GPS node, and
use qnx_adj_time() to resynch the two.

qnx_getclock() takes a pid/vc; it can be used to get the remote time.

-David
--
QNX Training Services
http://www.qnx.com/support/training/
Please followup in this newsgroup if you have further questions.

Stephen Thomas

Re: Time Synchronisation on Arcnet Network

Post by Stephen Thomas » Tue Dec 02, 2003 4:02 am

David Gibbs <dagibbs@qnx.com> wrote in message
news:bq7r6h$jcs$1@nntp.qnx.com...
Padraig Furlong <Padraig.Furlong@rte.ie> wrote:
Hi,
We have a number of Qnx4 PCs distributed over an arcnet network. One of
the
PCs is getting its time from a GPS receiver. What is the recommended way
to
distribute the time to the other Qnx4 PCs

The standard way of doing this is ntp -- but that uses TCP/IP for
communication, which isn't likely to work accross arcnet.

If sudden time jumps aren't a problem, I'd try something like:

rtc net <node_id_with_gps

On a regular basis.

But, that will give sudden time jumps. If you can't have sudden time
What about -r and -S options to minimize jumps?
jumps, I'd write a custom application that runs on a periodic basis
(timer driven, every 10 minutes? every hour? depends on how close
your time needs to be, and how quickly it drifts) that each time it
wakes up will get the local time, get the time on the GPS node, and
use qnx_adj_time() to resynch the two.

qnx_getclock() takes a pid/vc; it can be used to get the remote time.

-David
--
QNX Training Services
http://www.qnx.com/support/training/
Please followup in this newsgroup if you have further questions.

David Gibbs

Re: Time Synchronisation on Arcnet Network

Post by David Gibbs » Tue Dec 02, 2003 3:17 pm

Stephen Thomas <slthomas@corpdotolin.com> wrote:
David Gibbs <dagibbs@qnx.com> wrote in message
news:bq7r6h$jcs$1@nntp.qnx.com...
Padraig Furlong <Padraig.Furlong@rte.ie> wrote:
Hi,
We have a number of Qnx4 PCs distributed over an arcnet network. One of
the
PCs is getting its time from a GPS receiver. What is the recommended way
to
distribute the time to the other Qnx4 PCs

The standard way of doing this is ntp -- but that uses TCP/IP for
communication, which isn't likely to work accross arcnet.

If sudden time jumps aren't a problem, I'd try something like:

rtc net <node_id_with_gps

On a regular basis.

But, that will give sudden time jumps. If you can't have sudden time

What about -r and -S options to minimize jumps?
Yeah, that could work -- then you need cron running to run rtc on a
regular basis, too.

Custom application is probably lighter and easier.

-David
--
QNX Training Services
http://www.qnx.com/support/training/
Please followup in this newsgroup if you have further questions.

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