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<== Date ==> <== Thread ==>

Subject: RE: [EXTERNAL] Beckhoff BK9000 support survey
From: "Pearson, Matthew R. via Tech-talk" <tech-talk@aps.anl.gov>
To: "Dunning, Michael" <mdunning@slac.stanford.edu>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Thu, 27 Jun 2019 16:23:33 +0000
Hi,

> 
> One version uses only the epics modbus module.  This has no driver so requires
> less maintenance, but makes setting up IOCs more time consuming and results in
> a lot of code duplication.
> 

If the only problem with this method is the code duplication in each IOC then it's best to move the database into templates in a support module. Then all the IOC has to do is include them in a substitutions file. You could have one template per module type. And if there is common database code between modules then separate that out into common template files that are included in the per-module templates.

Then in the IOC startup script you may have a large list of calls to drvModbusAsynConfigure in order to setup the modbus ports for different address ranges. You can also put this in the support module, and just include it in the IOC st.cmd, passing in macros as necessary. For example, this is what I do for one of my applications for the Moxa ioLogik modules:

#E1214 Unit (6 DI and 6 Relay)
epicsEnvSet("IP_ADDR","192.168.200.177:502")
epicsEnvSet("IP_PORT","m1ip")
epicsEnvSet("PORT","m1")
< $(MOXA)/st_scripts/st_common.cmd

Where st_common.cmd is just a list of calls to drvModbusAsynConfigure. You may or may not need a different list for each type of module, depending on the modbus registry maps. 

> Another version uses asynPortDriver and some custom modbus code.  This is
> designed to make setting up IOCs easier, but requires maintenance of the driver
> code.

I would only do this if the application is complex enough that you need to move logic from the database down into C++ code. I'd still make use of the standard modbus support module and use it like a library to handle the modbus protocol (since it's been around for 10+ years and is well tested, that would be my starting point).

> 
> Another uses custom epics device support.  This requires writing device support
> for each bus terminal, and has resulted in a pretty ugly codebase.  This is our
> least favored solution going forward.
> 

There's no need to write support this way anymore, since Asyn gives you the device support for free. 

Cheers,
Matt



Replies:
Re: [EXTERNAL] Beckhoff BK9000 support survey Eric Norum via Tech-talk
Re: [EXTERNAL] Beckhoff BK9000 support survey Mark Rivers via Tech-talk
References:
Beckhoff BK9000 support survey Dunning, Michael via Tech-talk

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