Re: Help getting modbus module started

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

Hi Christian,

> But how do i have to define the ai(?)-record in FUrecords.db now, to read a single word from the given address 0x2103 using the IN_int function as defined above ?

You are using absolute Modbus addressing because you set the modbusStartAddress argument to drvModbusAsynConfigure to -1.   That means that the "offset" parameter in the record INP link field is the absolute Modbus address, 0x2103 in your case.  That is explained here: https://epics-modules.github.io/modbus/#epics-device-support

The record definition depends on what you want to do with the value in that register.  Perhaps the simplest is just to read it into a longin record.  

This is the example here: https://github.com/epics-modules/modbus/blob/master/modbusApp/Db/longin.template

# longin record template for register inputs

record(longin,"$(P)$(R)") {

    field(DTYP,"asynUInt32Digital")

    field(INP,"@asynMask($(PORT) $(OFFSET) 0xFFFF)")

    field(SCAN,"$(SCAN)")

}

You could load this as follows, for example:

dbLoadRecords("$(MODBUS)/db/longin.template", "P=IOC:, R=longin1, PORT=IN_int, OFFSET=0x2103, SCAN=1 second")

Note that because you are using absolute addressing the driver will not periodically poll, and you therefore cannot use SCAN=I/O Intr, you need to use a periodic scan rate, or Passive and arrange to processes the record some other way.

If the register contains an integer value that you want to convert to a double in engineering units then you could use an ai record with LINEAR conversion like this example: 

https://github.com/epics-modules/modbus/blob/master/modbusApp/Db/ai.template

# ai record template for register inputs

record(ai, "$(P)$(R)") {

    field(DTYP,"asynInt32")

    field(INP,"@asynMask($(PORT) $(OFFSET) $(BITS))MODBUS_DATA")

    field(LINR,"LINEAR")

    field(EGUL,"$(EGUL)")

    field(EGUF,"$(EGUF)")

    field(HOPR,"$(EGUF)")

    field(LOPR,"$(EGUL)")

    field(PREC,"$(PREC)")

    field(SCAN,"$(SCAN)")

}

The meaning of the BITS argument in the INP field is explained here: https://epics-modules.github.io/modbus/#asynint32.  If your A/D was 12-bit unipolar you would set BITS=12.  The EGU* fields set the values of the engineering units for the minimum and maximum values of the A/D, e.g. 0 and 4095 for a 12-bit A/D.  PREC is the number of digits you want EPICS to display, and the other fields are as above.

Mark

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Christian Pauly via Tech-talk <tech-talk at aps.anl.gov>
Sent: Tuesday, February 14, 2023 6:56 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: Help getting modbus module started

 

Great, thanks for the quick help !
Now it works, the ioc starts and is running.

But now i am stuck with defining a record using the modbus interface.

As a simpe start, I would like to read a single word (int16) from a
given address 0x2103 of master device with id=1, using modbus read
function type 3.
the relevant part of my st.cmd at the moment looks like this:

drvAsynSerialPortConfigure("RS485", "/dev/ttyUSB0", 0, 0, 0)
asynSetOption("RS485",0,"baud","9600")
asynSetOption("RS485",0,"parity","none")
asynSetOption("RS485",0,"bits","7")
asynSetOption("RS485",0,"stop","2")
asynOctetSetOutputEos("RS485",0,"\r\n")
asynOctetSetInputEos("RS485",0,"\r\n")
modbusInterposeConfig("RS485",2,1000,5)
drvModbusAsynConfigure(IN_int,"RS485",1,3,-1,1,UINT16,1000,0)
asynSetTraceIOMask("RS485",0,4)

## Load record instances
dbLoadTemplate "FUrecords.db"

But how do i have to define the ai(?)-record in FUrecords.db now, to
read a single word from the given address 0x2103 using the IN_int
function as defined above ?
without using template- and substitution files like in all examples i
found so far ?? (for sure that is the more clever way, but before i try
to understand that part i would like to have a running example first)

Thanks again for any help !

Christian





On 2/14/23 20:23, Pierrick M Hanlet via Tech-talk wrote:
> I almost forgot, you'll also need to add modbus to your
> $TOP/configure/RELEASE file (assuming that you have the modbus module).
> This may not be precisely worded, but when adding a module, you need to
> define its path in $TOP/configure/RELEASE and then
> add the modules (lib / dbd) to the $TOP/xxxApp/src/Makefile.
> Cheers,
> Pierrick
>
>
>
> On 2/14/23 13:02, Pierrick M Hanlet via Tech-talk wrote:
>> Hi Christian,
>> You will also need to add some things to your xxxApp/src/Makefile:
>> - xxx_DBD+=modbusSupport.dbd
>> - xxx_DBD+=drvAsynSerialPort.dbd
>> - xxx_LIBS+=modbus
>>
>> I think that this should do it for you.
>> Good luck,
>> Pierrick
>>
>>
>> On 2/14/23 11:38, Christian Pauly via Tech-talk wrote:
>>> Hi folks
>>>
>>> I am trying hard to set up a Raspberry running an EPICS IOC for a
>>> Delta VFD motor driver / frequency inverter. The device is controlled
>>> via modbus, using a large set of individual 16bit integer read/write
>>> registers for configuration, and few more registers for control.
>>> At the moment it is configured to talk Modbus ASCII via RS485, and
>>> with a simple Python program using minimalmodbus-lib i can talk to the
>>> controller.
>>>
>>> Now i started with a fresh EPICS 3.15.7 base, (in ~/EPICS/base) and
>>> installed ASYN-R4-43 (~/EPICS/modules/asyn-R4-43) and modbus
>>> (~/EPICS/modules/modbus_R3-2).
>>> I initiated a new application ~/EPICS/projects/FUcontrol,
>>> ran "makeBaseApp.pl -t example FUcontrol", "makeBaseApp.pl -i -t
>>> example FUcontrol" - and thats basically it.
>>>
>>> And now i am stuck how to include modbus (includes / libs / dbd files)
>>> into my exampleApp.
>>>
>>> I kind of managed to include ASYN already by adding
>>>     ASYN=... to the RELEASE file
>>>
>>> and to the Makefile:
>>>     FUcontrol_LIBS += asyn
>>>
>>> In my ioc startup st.cmd i can run the commands
>>> drvAsynSerialPortConfigure("RS485", "/dev/ttyUSB0", 0, 0, 0)
>>> to configure the interface.
>>>
>>> But if i add
>>> modbusInterposeConfig("RS485",2,1000,0)
>>> i get an error on startup claiming that modnusinterposeconfig can not
>>> be found.
>>>
>>>
>>> So:
>>> Is there any simple step-by-step instructions how to add modbus to an
>>> existing ioc application ?
>>> I could not find anything "simple" in the documentation. I saw the
>>> examples which come with modbus, but all these already look quite
>>> complicated to me...
>>>
>>> Or any good advise on how to continue from here ?
>>>
>>> Thanks for any help !
>>>
>>> Christian
>>>
>>>
>>>
>>>
>>>
>