RE: ASLO doesn't work

["Mercado, Ronaldo \(DLSLtd, RAL, LSCI\) via Tech-talk" <tech-talk at aps.anl.gov>]

I can confirm that Ben has correctly diagnosed that device support returns "2" (no convert) for float data types.

The code below comes from S7nodaveAiRecord.h of s7nodave (https://oss.aquenos.com/epics/s7nodave/ )
The comments have mode details.

    virtual long processRecord()
    {
        long status = S7nodaveInputRecord::processRecord();
        if (status == RECORD_STATUS_OK) {
            // If the PLC is using the float data-type, we do not want the                                                                                                               
            // VAL field of this record to be overwritten with a value                                                                                                                   
            // calculated using the RVAL field. Instead we use the VAL field                                                                                                             
            // directly. We signal this to the record's readValue routine by                                                                                                             
            // returning the special value RECORD_STATUS_OK_NO_CONVERT instead                                                                                                           
            // of RECORD_STATUS_OK.                                                                                                                                                      
            if (this->recordAddress->getPlcDataType() == plcDataTypeFloat) {
                return RECORD_STATUS_OK_NO_CONVERT;
            } else {
                return RECORD_STATUS_OK;
            }
        } else {
            return status;
        }
    };

Cheers,
Ronaldo

-----Original Message-----
From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Ben Franksen via Tech-talk
Sent: 17 September 2020 16:02
To: tech-talk at aps.anl.gov
Subject: Re: ASLO doesn't work

Am 17.09.20 um 11:10 schrieb Vishnu Patel via Tech-talk:
> I have tried to divide the value of ai record using ASLO field. But It doesn't work.
> 
> record(ai, "AI0") {
>     field(DTYP,"s7nodave")
>     field(INP,"@lcpcPLC DB6.DBD36 float")
>     field(LINR,"LINEAR")
>     field(HOPR,"20")
>     field(LOPR,"0")
>     field(ASLO,"0.001")
>     field(PREC,"4")
>     field(SCAN,"1 second")
>     field(EGU,"Bar")
>     field(EGUF,"32767")
>     field(EGUL,"-32768")
> }

None of the replies so far have offered an explanation of exactly /why/ this doesn't work. Judging from the aiRecord.c code and the format of the INP link, I venture that the device support indicates to the record support that it already did the conversion and wrote the VAL field by returning 2 instead of 0 from its read() method. To teh record support this indicates that it should completely ignore all conversion related fields (RVAL, LINR, EGUF, EGUL, ASLO, AOFF, ESLO, EOFF, ROFF).

Cheers
Ben


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