Experimental Physics and
Industrial Control System

"Dunning, Michael via Tech-talk" <[email protected]> · Thu, 27 Jun 2019 14:38:00 -0700

Thanks everybody for the responses so far.

I should add that, as Davide mentioned, for some modules we need to
access the Beckhoff "hidden" registers which can only be accessed
through other registers.  This makes the modbus "driver" approach
necessary if we want to cover all modules.  In our case we've needed
to access these registers for changing configuration parameters, e.g.
changing thermocouple types or ADC scaling, or for motor
configuration.

Mark - thanks for pointing out the new C++ version of modbus.  It
sounds like we could get rid of our custom modbus driver code and
instead call modbus functions directly from our asynPortDriver.  This
should simplify things and make maintenance a bit easier.  This
definitely sounds like something we should pursue.

Thanks again to all who have responded.

Mike

Michael Dunning
SLAC National Accelerator Laboratory
2575 Sand Hill Road
Menlo Park, CA 94025
(650) 926-5200
On Thu, Jun 27, 2019 at 11:52 AM Mark Rivers <[email protected]> wrote:
>
> > 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
>
> In the new asynPortDriver branch you can do the following:
>
>
>
>         drvAsynIPPortConfigure("Koyo1","camaro:502",0,0,1);
>         asynSetOption("Koyo1", 0, "disconnectOnReadTimeout", "Y");
>
>
>
>         modbusInterposeConfig("Koyo1", modbusLinkTCP, 5000, 0);
>
>
>
>         // Use absolute addressing, modbusStartAddress=-1.
>         drvModbusAsyn *pModbus = new drvModbusAsyn("K1", "Koyo1", 0, 2, -1, 256, dataTypeUInt16, 0, "Koyo");
>
>         // Write 10 bits at address 2048
>         memset(data, 0, sizeof(data));
>         data[0] = 1;
>         data[2] = 1;
>         data[4] = 1;
>         data[6] = 1;
>         data[8] = 1;
>         printf(" Writing [1 0 1 0 1 0 1 0 1 0] to adddress 2048\n");
>         /* asynStatus doModbusIO(int slave, int function, int start, epicsUInt16 *data, int len); */
>         pModbus->doModbusIO(0, MODBUS_WRITE_MULTIPLE_COILS, 2048, data, 10);
>
>
>
>         Because the drvModbusAsyn constructor was called with startAddress=-1 doModbusIO can write to any address with any function code.
>
> Mark
>
> Sent from my iPhone
>
> On Jun 27, 2019, at 12:23 PM, Pearson, Matthew R. via Tech-talk <[email protected]<mailto:[email protected]>> wrote:
>
> 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
>
>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System