RE: The INP field

[Mark Rivers <rivers@cars.uchicago.edu>]

I second what Nick has said.  If you use asyn then you should be able to use the standard asyn device support.  You only need to write an asyn port driver.  If you base that on the asynPortDriver C++ base class then most of the overhead of configuring the asyn port driver is taken care of for you, and the amount of code you need to write is minimized.

 

Mark

 

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of nick.rees@diamond.ac.uk
Sent: Wednesday, February 06, 2013 8:15 AM
To: brunoseivam@gmail.com; tech-talk@aps.anl.gov
Subject: RE: The INP field

 

Hi Bruno,

 

While I don’t know anything about your particular device, in general I would recommend using the asynDriver framework for new devices. This already does most of the legwork for you and you only have to write one layer of support. Also, despite its name, it works with synchronous as well as asynchronous devices.

 

Cheers,

 

Nick Rees

Principal Software Engineer           Phone: +44 (0)1235-778430

Diamond Light Source                  Fax:   +44 (0)1235-446713

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Bruno Seiva Martins
Sent: 06 February 2013 13:34
To: tech-talk@aps.anl.gov
Subject: The INP field

 

Hi everyone,

 

I'm writing both device and driver support layers for my custom device. I'm trying to make them as generic as possible, but for that purpose I need to pass them some configuration parameters.

 

They interface with common records: AI, AO, BI and BO. I'm trying to pass those configurations parameters, via INP/OUT field of those records. There are four parameters I would like to pass. For instance, I would like to be able to do something like:

 

record(ai, "LOCON$(Addr):ai")

{

    field(DTYP, "LocoAi")

    field(DESC, "Local Converter Analog Input")

    field(SCAN, "1 second")

    field(INP,  "$(Addr).$(Param1).$(Param2).$(Param3)")

    field(PREC, "3")

    field(EGU,  "Volts")

    field(LINR, "LINEAR")

}

 

Notes: The separator must not necessarily be the dot character, could be anything. All four parameters are numerical.

 

Then I would like to parse the resulting string in my init_record code:

 

//...

char configString[40] = {0};

recGblInitConstantLink(&record->inp, DBF_STRING, configString);

// parse config string

 

 

This won't work. And the documentation is very clear about that:

 

http://www.aps.anl.gov/epics/EpicsDocumentation/AppDevManuals/RecordRef/Recordref-5.html#MARKER-9-11

 

"Input link fields and desired output location fields can specify a constant instead of a hardware or database address. A constant, which is not really an address, can be an integer value in whatever format (hex, decimal, etc.) or a floating-point value. "

 

BUT I can access that resulting string using:

 

record->inp.value.constantStr

 

 

Now, I have several questions I couldn't find the answers by myself:

 

1. Is there another way of passing several (in my case, four) numerical parameters from the record to the device support? Right now I'm accessing the string using record->inp.value.constantStr, but this feels dirty and hacky. 

 

2. I could pack those four values into one unsigned long value, as each one of them is one byte long, but this wouldn't be recommended, would it?

 

3. If the INP field (when CONSTANT) is a number only (and I have tested the outputs of recGblInitConstantLink with several inputs to confirm that), what is the purpose of that constantStr field in the value union? Is it just to hold the value before it is parsed?

 

4. Will I have to write new records or record supports?

 

 

Thanks in advance!

 

Best regards!

 

Bruno