LinuxCNC with EtherCat on a Beckhoff CX2040 [Part 2]

In my previous post on this topic I successfully managed to get LinuxCNC with EtherCat running on a Beckhoff CX2040. That was over a year ago and since then I didn’t have the time to dig deeper into the matter. Until now, and a lot has changed in the meantime …

Last weekend I attended DDos at the Odenwilusenz Hackerspace in Beringen, Switzerland. In the days before that, I planned to reactivate my setup and bring it along.

When I started the system, everything worked exactly like when I left it. So I added a Beckhoff EL1804 and as Beckhoff EL2828 just to find out that the used version of the linuxcnc-ethercat does not sopport these two types.

An attempt to update to the latest version failed. So I looked at the LinuxCNC website to check out what’s the latest version. I ran 2.8.4 and the latest release was 2.9.3 which, to my surprise now comes from a debian repo along withthe latest version of linuxcn-ethercat. And that also includes the CCAT driver which I had to build from source the last time.

So I decided to start all over and install the 2.9.3 ISO on a new CF card.

Installation 🔗

The installation was straight forward as expected. After booting the system for the first time, I got an error at the attempt to do a system update.

The reason is a missing or wrong GPG key in the sources.list

However, the recommended solution from the LinuxCNC forum didn’t work for me, but I was able to use the instructions from the Etherlab website

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export KEYRING=/usr/share/keyrings/etherlab.gpg
curl -fsSL https://download.opensuse.org/repositories/science:/EtherLab/Debian_12/Release.key | gpg --dearmor | sudo tee "$KEYRING" >/dev/null
echo "deb [signed-by=$KEYRING] https://download.opensuse.org/repositories/science:/EtherLab/Debian_12/ ./" | sudo tee /etc/apt/sources.list.d/etherlab.list > /dev/null

This adds a new file called etherlab.list to /etc/apt/sources.list.d/, which requires that the original .list file is deleted.

After that I was able ti update and upgrade with

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sudo apt update
sudo apt upgrade

I installed LinuxCNC and linuxcnc-ethercat from the repo

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sudo apt install ethercat-master libethercat-dev linuxcnc-ethercat

Then I enabled and started the EtherCat Master

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sudo systemctl enable ethercat.service
sudo systemctl start ethercat.service

That failed because I was missing configuration in /etc/ethercat.conf. The config file requires two settings MASTER0_DEVICE and DEVICE_MODULES. To get the MAC of eth0 which is the CCAT simply run ip a and read the MAC address from there.

I set MASTER0_DEVICE="00:01:05:1e:6b:8e" and DEVICE_MODULES="ccat"

Luckily the Etherlab master comes with prebuild ccat drivers.

After a reboot there was still no /dev/EtherCAT device 🤔

So I ran sudo systemctl restart ethercat.service and that worked.

The LinuxCNC forum recommends to add a udev rule for correct permissions, so I added /etc/udev/rules.d/99-ethercat.rules with this content:

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KERNEL=="EtherCAT[0-9]", MODE="0777"

After another reboot /dev/EtherCAT was gone again. sudo systemctl restart ethercat.service brought it back.

At the time of writing this I was not able to figure out whats causing this and how to fix it other than running a sudo systemctl restart ethercat.service after every system start.

Testing EtherCat 🔗

I quickly checked if the master was running

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ethercat master

Master0
  Phase: Idle
  Active: no
  Slaves: 3
  Ethernet devices:
    Main: 00:01:05:1e:6b:8e (attached)
      Link: UP
      Tx frames:   18587429
      Tx bytes:    1299386046
      Rx frames:   18587422
      Rx bytes:    1596784378
      Tx errors:   0
      Tx frame rate [1/s]:    122    121    121
      Tx rate [KByte/s]:      7.1    7.1    7.1
      Rx frame rate [1/s]:    122    121    121
      Rx rate [KByte/s]:      9.1    9.0    9.0
    Common:
      Tx frames:   18587429
      Tx bytes:    1299386046
      Rx frames:   18587422
      Rx bytes:    1596784378
      Lost frames: 7
      Tx frame rate [1/s]:    122    121    121
      Tx rate [KByte/s]:      7.1    7.1    7.1
      Rx frame rate [1/s]:    122    121    121
      Rx rate [KByte/s]:      9.1    9.0    9.0
      Loss rate [1/s]:          0      0      0
      Frame loss [%]:         0.0    0.0    0.0
  Distributed clocks:
    Reference clock:   Slave 0
    DC reference time: 0
    Application time:  0
                       2000-01-01 00:00:00.000000000

Nice 😎

Creating a test config 🔗

I started LinuxCNC with the sim.axis config to have a template to start with.

In the [HAL] section of axis.ini I added a HALFILE = ethercat.hal.

Next I created two new files in the same folder, ethercat.hal and ethercat-config.xml.

The first looks like this:

loadusr -W lcec_conf ethercat-conf.xml
loadrt lcec
addf lcec.read-all              servo-thread
addf lcec.write-all             servo-thread

The later like this

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<masters>
    <master idx="0" appTimePeriod="1000000" refClockSyncCycles="-1" name="master0">
        <slave idx="0" type="EL1018" name="DI1"/>
        <slave idx="1" type="EL2008" name="DO1"/>
    </master>
</masters>

I switched my setup back to the old EL1018 and EL2008 terminals because I knew they were working in the old setup.

After starting LinuxCNC with this config I was able to see inputs in the Show HAL configuration menu under Pins -> lcec -> Master0.

Overall a very easy setup compared to what I had to do last time.

Nice work from the people at LinuxCNC , Etherlab/IgH and linuxcnc-ethercat