[time-nuts] Industrial control systems and IEEE 1588v2 time sync

Peter Bell bell.peter at gmail.com
Wed Jul 31 04:53:40 UTC 2013


I was involved in some work on industrial controls that used 1588 for
timing.  We only needed microsecond accuracy, and it did that easily - the
basic hardware is simple, we were using STM32 microcontrollers with the
DP83640 PHY.  Since the MCU required a PHY anyway, the additional cost for
the IEEE1588 support was about $3.50/unit ($5 rather than $1.50 in 1000 up
quantities).

The PHY chip also has a (programmable) clock output locked to the 1588
timing, but it appeared to have quite a lot of phase noise on it - I didn't
bother doing any detailed measurements because we weren't actually using it.



On Wed, Jul 31, 2013 at 12:19 PM, Bill Hawkins <bill at iaxs.net> wrote:

> Group,
>
> Has anyone used IEEE 1588 to synchronize clocks on an Ethernet network?
>
> I was involved in the design of time sync for Foundation Fieldbus circa
> 2000.
> We needed one millisecond accuracy, so we went with SNTP on local
> networks.
> I've just seen an ad for a switch that can do 1588, and looked up what
> it does.
>
> Microsecond accuracy is impressive, but what does it cost?
>
> Industrial sensors are generally sampled at about 10 millisecond
> intervals out
> to several seconds. SNTP would appear to be very adequate for time
> stamps as
> there is uncertainty introduced by when the computer gets around to
> sampling
> the sensor in its sampling and control cycle.
>
> Any thoughts appreciated.
>
> Bill Hawkins
>
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