[Etherlab-users] Embedded PC with out of the box support for igh-ethercat

[Graeme Foot]

Hi Nicola,

We've been using Beckhoff CX2020's for around 12 years on over 300 machines running at 1000Hz (1ms).  They are now end of life'ing so have nearly completed updating our system to be able to work with CX5230's (needed new Linux kernel etc).  They are a bit slower than the CX2020's but have the power we need for our machines.  We run them headless connected to a Windows HMI PC.

If we need more power or a faster cycle in the future we've also briefly tested the new Ryzen CX2033 which looks like it runs around 3 times faster than the CX5230 for our system.

We build our system using Buildroot with the EtherLab EtherCAT master and RTAI.  We've never used an arm based CPU, just x86 (and now x86_64).

So, the Beckhoff PC's in our experience are fine for Linux.  Each system has an order code for purchasing it with a blank disk (aka no operating system or TwinCAT).  You just need to get past the hard sell.  Of course you are on your own once you buy it if it's not a hardware issue as they know nothing except TwinCAT, but that's the case with any PC you go with.

A summary of our system:
* CX2020 (soon to be CX5230)
* Linux 2.6.32 32bit (and now Linux 4.19 64bit)
* Our application uses approx. 21-35% of CPU time @ 1000Hz on CX2020 (25-63% on the CX5230, slower CPU and 64bit is a bit slower than 32bit Linux)
* RTAI
* thttpd to provide a web based configuration and diagnostic interface
* The majority of the root filesystem is provided by initrd with mount points for a small amount of config files that need permanent storage (CFast cards).  So very minimal and infrequent HDD access and no problems with power outages or storage corruptions.  On a normal machine shutdown we do send a halt command to Linux to be nice.  We have had one CFast card release it's magic smoke, but we don't know why, we suspect it was a hardware failure.
* A couple of decades ago we had UPS's on a few machines, but the UPS's would fail more often than there were power cuts.  Also our machines can't do anything without power, so for us its just better to let the system turn off.
* We've used FSoE on four machines (using the EK1960 and various other TwinSAFE modules).  It was a machine with complex safety requirements (light curtains, deadman switches, bypasses plus other).  I wrote a Mailbox Gateway server for the EtherLab master so you could download the safety program to the TwinSAFE PLC (using the TwinSAFE Loader program supplied by Beckhoff) via the EtherLab master.  We looked at the costings of FSoE vs a standard Safety Relay on our standard machines a while back and although it was close FSoE was more expensive and more complex so we stayed with Safety Relays.

Regards,
Graeme


-----Original Message-----
From: Etherlab-users <etherlab-users-bounces at etherlab.org> On Behalf Of Fontana Nicola
Sent: Friday, November 24, 2023 9:37 PM
To: etherlab-users at etherlab.org
Subject: [Probable Spam] [Etherlab-users] Embedded PC with out of the box support for igh-ethercat

Hi all,

I'm in the process of trying to "standardize" the hardware stack I'm using

My requirements are:

1. a PC easily connectable to EtherCAT
2. native support for igh-ethercat
3. OPC/UA server via open62541
4. reliable 5 ms scan time

Lately I'm using Beckhoff CX9020-0100 but its performances are (mildly
put) crap. I fear to use other Beckhoff solutions because they seem to not support Linux natively (the fact that they keep pushing for TwinCAT is quite annoying).

I am also quite interested to know what do you use in general, how do you handle power outages (or more general the poweroff procedure) to avoid storage corruptions and if you use FSoE. Those would be a really great FAQs.

Thank you.
--
Nicola

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