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

Daniel Mendes dmendesf at gmail.com
Thu Aug 1 17:48:32 EDT 2013


This is true, but what´s needed to generate the sync packets? I think 
they call them "Grand Masters", and cost a lot of money... Is there any 
cheap approach for this end of the problem?

Daniel

Em 31/07/2013 08:03, Bob Camp escreveu:
> Hi
>
> A number of the chip guys will sell you micro's that have one or more 1588 ethernet ports on them. Some of them are in the sub $10 range. With a bit of Time Nut attention, they seem to be capable of well under 1 us performance. If you have a daisy chain network they will do what you need without any switches.
>
> As mentioned above, if your network has modern (gigabit rather than 10 megabit) switches on it, you can likely get to 1 us without any fancy time stamping switches. There are a few other minor details you would want to pay attention to, but they are manageable for a shop floor network.
>
> Bob
>
> On Jul 31, 2013, at 12:19 AM, 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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