[Etherlab-users] Running a large number of slaves

Wed Apr 21 10:10:18 CEST 2021

Hello again,

I tried running the ethercat master with a large PDO domain, but with no success.

Following
https://sourceforge.net/u/uecasm/etherlab-patches/ci/default/tree/#readme
I built the ethercat master with Gavin's patch set.

I'm running on a x86 Intel Atom dual core with linux kernel 3.18.48. Ethernet adapter is igb.

To achieve a very large PDO volume I created 2 ecat slaves, each with PDO data worth of 917 bytes.

When connecting only 1 slave, and running examples/user/ec_user_example I can raise the slave to OP and exchange data between the master and slave over PDO.

When connecting 2 slaves the start up process of the ethercat master gets stuck after

EtherCAT DEBUG 0-main-0: Checking system time offset.

And according to a wireshark capture the communication completely stops even though the application is still running cyclically.

Can you please help me setup a functional system?

Thanks,

Nir.
________________________________
From: Etherlab-users <etherlab-users-bounces at etherlab.org> on behalf of Geller, Nir <nir.geller at servotronix.com>
Sent: Wednesday, March 31, 2021 1:48 PM
To: Gavin Lambert <gavin.lambert at tomra.com>; Richard Hacker <ha at igh.de>; etherlab-users at etherlab.org <etherlab-users at etherlab.org>
Subject: Re: [Etherlab-users] Running a large number of slaves

Hi Gavin,

This sounds promising.

With regard to cyclic real time performance, does fragmentation work properly and efficiently with slaves that support DC?

Thanks,

Nir.

-----Original Message-----
From: Gavin Lambert <gavin.lambert at tomra.com>
Sent: Tuesday, March 30, 2021 9:40 AM
To: Geller, Nir <nir.geller at servotronix.com>; Richard Hacker <ha at igh.de>; etherlab-users at etherlab.org
Subject: RE: [Etherlab-users] Running a large number of slaves

Yes, it splits to multiple packets automatically.  Just be careful to not use more data than your cycle rate will allow.

Note that initialization and configuration of a large number of slaves is very slow by default, as it occurs in series.
The unofficial patchset changes this to occur in parallel (for groups at a time rather than the whole network, to avoid creating too many packets at once).

Gavin Lambert
Senior Software Developer

COMPAC SORTING EQUIPMENT LTD | 4 Henderson Pl | Onehunga | Auckland 1061 | New Zealand
Switchboard: +49 2630 96520 | https://www.tomra.com

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-----Original Message-----
From: Geller, Nir
Sent: Tuesday, 30 March 2021 1:23 am
To: Richard Hacker <ha at igh.de>; etherlab-users at etherlab.org
Subject: Re: [Etherlab-users] Running a large number of slaves

Hi,

Thanks for your reply.

You mean that in the case of a large amount of PDO data ( > 1500), a single invoke of ecrt_master_send(master) will result several frames sent out 1 after another?

Nir.

-----Original Message-----
From: Etherlab-users <etherlab-users-bounces at etherlab.org> On Behalf Of Richard Hacker
Sent: Monday, March 29, 2021 3:09 PM
To: etherlab-users at etherlab.org
Subject: Re: [Etherlab-users] Running a large number of slaves

EtherCAT and the master are not limited to the ethernet packet size.
EtherCAT frames are automatically divided into smaller ethernet packets as required. As long as you're not exceeding physical limits, (like sending ~1,5kb at a rate of 1kHz), you should be fine.

Physically EtherCAT can address ~64k slaves on a network.

On 2021-03-29 13:22, Geller, Nir wrote:
> Hi There,
>
> I'm trying to setup one ethercat master with a very large number of
> ethercat slaves.
>
> The first obstacle I'm thinking about is a very large amount of data
> sent over PDO each cycle, that will definitely exceed 1500 bytes.
>
> In order to address this issue I want to understand if it is possible
> to send more than one frame each cycle?
>
> Another method could be using jumbo frames. Does the ethercat master
> support that?
>
> Does anybody have practical experience with such a setup?
>
> Thanks,
>
> Nir.
>
>

Mit freundlichem Gruß

Richard Hacker

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