EtherCAT + Nerves

I’ve worked with EtherCAT. Nerves uses Buildroot which includes an EtherCAT package igh-ethercat. It goes through the standard network stack. It also has a few hardware drivers such as e100 for better performance. To include it you need to make a custom Nerves system and add the package.

Ultimately, we found it didn’t have the performance we needed for our specific hardware. So we made a custom, private Nerves system that uses Acontis’s EtherCAT offering.

Thanks for the answer, you give me a good path to follow !!! :).

If you do not mind to tell us, did you used the nerves official supported hardware or another one?
I’m asking it because I’m planning to use a Rpi3 and I want to know if it’s worth to looking at igh-ethercat or directly to the Arcontis, or which were your performance limitations that igh-ethercat doesn’t accomplished?
Also I want to ask:
In your opinion, which package is more friendly to use (or to make an elixir wrapper)?

Thanks in advance…

We had problems with igh-ethercat with raspberry pi. It simply couldn’t compile the igh-ethercat package. We never figured out why. It worked with BeagleBone Black and that’s what we’re still using.

We needed sub-millisecond response times on EtherCAT. igh-ethercat doesn’t provide hardware drivers for BBB (or RPi). So it was taking several milliseconds for a round trip.

If you don’t need that level of performance, then go with igh-ethercat. It’s also open source. Actontis provides proprietary, enterprise-level solutions so you’ll be paying quite a bit for it.

Hi all, here is an update of this thread; first, I tried to build igh-ethernet package in buildroot for a rpi3, however, since rpi3 doesn’t have any igh-ethernet supported hardware. The igh-ethernet needs to be compiled with --enable-generic option, therefore, I needed to add a custom igh-ethernet package to buildroot, also I enabled udev, taskset packages. Despite this, I had these types of warnings during compilation:

depmod: WARNING: /home/alde/Documents/Elixir/Nerves/repos/valiot_system_rpi3/.nerves/artifacts/valiot_system_rpi3-portable-1.7.2-valiot.7/target/lib/modules/4.19.25/extra/devices/ec_generic.ko needs unknown symbol kernel_bind

depmod: WARNING: /home/alde/Documents/Elixir/Nerves/repos/valiot_system_rpi3/.nerves/artifacts/valiot_system_rpi3-portable-1.7.2-valiot.7/target/lib/modules/4.19.25/extra/master/ec_master.ko needs unknown symbol sched_setscheduler
.
.
.

The following error was shown during runtime:

iex(3)> cmd "modprobe ec_master"
modprobe: can't load module ec_master (extra/master/ec_master.ko): unknown symbol in module, or unknown parameter
1

At this point I thought it could be a kernel version issue, since when compiling a similar repository (for bbb), the compilation works without warnings, therefore, I lost interest in using igh-ethernet haha.

The second option was the arcontis software atemsys, which it appears to be easier to compile, so I added a custom package to buildroot, however, during compilation I had the same type of warning (only 1 warning) as before:

depmod: WARNING: /home/alde/Documents/Elixir/Nerves/repos/valiot_system_rpi3/.nerves/artifacts/valiot_system_rpi3-portable-1.7.2-valiot.7/target/lib/modules/4.19.25/extra/atemsys.ko needs unknown symbol of_find_compatible_node

Therefore, it also fails at runtime.

My third option was the SOEM project, I had no issue with this library (compiles with no warnings), however, this package is refered by the community more as a library than a master software, therefore, I think that its better to make an Elixir wrapper than add the package in buildroot.

Giving another chance to the previous options (atmsys, igh-ethernet) and looking the bbb project, it seems that by disabling CONFIG_TRIM_UNUSED_KSYMS=y in linux-x.x.defconfig both packages works in runtime !!!

The option CONFIG_TRIM_UNUSED_KSYMS=y seem to be to trim exported kernel symbols that are not used, which for me seems that it makes the opposite, I also do not know what kind of problems I am creating when disabling this option :(, Does anyone knows?

Currently, the problem in which I am working with igh-ethernet is to open a device /dev/EtherCAT0 that does not exist, but I think it’s a matter of executing some package commands and defining some rules in /etc/udev/rule.d (this directory does not exist either).

Does anyone know how to define these rules in Nerves?, or does it have to be done in Buildroot?

Regards.

If anyone is still stumbling upon this problem, I’ve written two libraries which are both running on <10ms cycle time on a Rpi4:

• igh_ethercat (a wrapper for IgH EtherCAT written with Zigler)
• ethercat (written in pure Elixir)