CODESYS - the IEC 61131-3 automation software

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PostPosted: Fri May 22, 2015 7:31 pm 

Joined: Fri May 22, 2015 3:53 pm
Posts: 4
Is it possible to create a custom device file to describe the registers available in a Modbus RTU slave? If so, how is it done?

We use a lot of Automation Direct GS2 series VFDs, and I would like to spend the effort on creating a device description so that I can do each project more easily.

PostPosted: Fri May 29, 2015 3:49 pm 
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Joined: Fri Sep 02, 2011 8:02 pm
Posts: 301
That would be nice - I hope it is so. In the meantime, you can create a structure with name:register pairings to make your life a bit easier (e.g. Read(Register.CmdSpeed)). Or even a complete FB with properties for each register handling read/write requests implementing the structure. At least then you have a module you can export/import (or save as library) for future reuse.

Scott Cunningham
KEB America, Inc.

PostPosted: Mon Nov 13, 2017 1:52 pm 

Joined: Fri Nov 23, 2012 11:42 am
Posts: 54
It is possible to create custom modbus slaves, both TCP and RTU with varying levels of customisation.

At the simplest it is possible to have a custom device descriptor with a name associated with some or all of the registers and coils on the slave making integration easier - no more looking up register addresses.

The next level of integration can pre-define channels. i.e. as soon as the device is added to a project then the Channels are already defined, all thet is required is for the parameters to be mapped into the application.

A further level of integration allows the installation of the device to add a library to the Library Manager, and create a function block in the IOConfigGlobals and map parameters from the defined channels into the function block. If this is done for all required parameters then all that is required to use the device is to add it to the project and then use variables directly in the application.

In all of these cases it is then possible to modify the pre-defined channels and mappings and to add more channels as required in the same way as for any CODESYS device.

The effort to create a custom modbus slave varies significantly depending on the level of customisation, the number of registers and coils, and how the address space of the slave device is specified. I have created custom modbus devices for several device vendors already. If you wish to discuss this further please contact me

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