Experimental Physics and
Industrial Control System

<[email protected]> · Fri, 18 Sep 2015 21:21:10 +0000

Hi Matt,

I think this is basically because RVAL is an integer and the conversions happen when you convert the integer to a float. Any device support that returns float must put it in the VAL field and return a do not convert status. I have always thought we should have a record identical to the ai record but with a floating point RVAL.

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

-------- Original message --------
From: "Pearson, Matthew R."
Date:18/09/2015 21:51 (GMT+00:00)
To: "[email protected] list"
Subject: ai record doesn't do convert for floats?

Hi,

I’m wondering why it’s convention that the ai record doesn’t use its convert function when using some types of device support routines. The analog value read function should return status=2 according to the IOC developers guide, and this causes it to not do any LINR type conversion on the VAL field.

I’m wondering why I can’t do this:

record(ai, "$(S):SE:CH1:PVRaw")
{
  field(DESC, "Process Variable CH1")
  field(DTYP, "asynFloat64")
  field(INP, "@asyn(n1,0,1)")
  field(SCAN, "I/O Intr")
  field(LINR, “SLOPE”)
  field(ESLO, “0.1”)
}

whatever the device support routine passes to the ai record is what I get in VAL. So to do slope conversions I have to pass it to another ai record using soft channel device support.

Although, I’ve found that using asynInt32 support does return 0 to the record support, causing the conversion to happen to VAL. I believe ai support in streamDevice does the same.

Cheers,
Matt

Spallation Neutron Source
ORNL

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System