[Etherlab-users] Communication in External Mode in Simulink

[Laurens Jacobs]

Dear EtherLab users and developers

I'm currently setting up a real-time Linux machine to be used with a custom EtherCAT slave. So far, I have successfully installed and configured the EtherCAT master, PdServ, and the EtherLab library for use with Simulink. I had to make some minor changes in the includes of the build configuration to make things work, but I'm at the point where I can build a Simulink model for stand-alone use and run it on my machine. I can verify by my external hardware the executable is doing exactly what it is supposed to do, so that's great. I can also build the Simulink model for 'monitoring and tuning', which is what I eventually would like to do in order to log data and change parameters online. The build process for that also works fine, but whenever I try to "connect" to the target hardware (which is the real-time Linux machine itself essentially), it throws the following error:

 > External mode MEX-file 'noextcomm' does not exist or is not on the MATLAB path. Note that the MEX-file name entered should not have a file extension.

I was wondering if anyone has experienced this issue before and knows how to resolve it. I read that it is a known issue (see, e.g., <https://github.com/SchapplM/etherlab-examples/blob/master/SETUP_ETHERCAT.MD#meldung-external-mode-mex-file-noextcomm>, which I also used as a guideline to configure my Simulink model parameters) but there is no real root-cause mentioned, nor do the suggestions listed there resolve the problem. Apart from that link, there seems to be little information to be found online about this issue. I'm willing to further debug the problem myself, but it is unclear to me how this 'noextcomm' binary is used - I can't find any references in the source or header files in the MATLAB root, nor in the EtherLab source files. If anyone has any pointers in that direction, sharing them would be greatly appreciated. I will also get in touch with Mathworks support to see whether they can shed a brighter light on this (as there is not much about it in the documentation). 

For the sake of completeness, here are the versions I'm using:
- EtherCAT Master 1.6.1 (release, 419f6216)
- PdServ at the latest master branch (f3195b28)
- EtherLab at the latest master branch (8dfa661f)
- MATLAB 9.7.0.1737446 (R2019b) Update 9 + Simulink version 10.0
- Linux 6.1.112-rt43 #1 SMP PREEMPT_RT

Best regards
Laurens

--
Laurens Jacobs | Postdoctoral researcher - Mechatronics & control systems
http://www.mech.kuleuven.be/meco
Division RAM, Dept. of Mechanical Engineering, KU Leuven
laurens.jacobs at kuleuven.be, +32 16 37 35 44