Re: When an external device does not provide termination on TCP ASCIIstream replies

[Burkhard Kolb <b.kolb@gsi.de>]

Allison, Stephanie wrote:
> Hi Mark,
>
> Thanks for your reply.  I'm currently using stream version 2.2 and asyn version 4.9 on epics base 3.14.8.2.  I'm unable to get stream to work without timeout when the InTerminator is set to "" (meaning no terminator) and MaxInput=0.  Stream/asyn always waits ReadTimeout even though it has received the reply (it just doesn't know it has the *complete* reply).   If I set maxInput to a large number, then it also waits ReadTimeout waiting for extra input it'll never receive.
>
> I would really like to use stream instead of writing my own support on top of asyn just for this case.  Does anybody know how can I set up stream so that the InTerminator is "", maxInput is 100, but there is no need to wait for anything more after something...anything > 0 chars is received?   I still want to use a reasonable ReadTimeout for when things slow down a bit on the network.  Maybe I can use devGpib for this case, though stream would be better.
>
> Thank you,
> Stephanie
>
> > -----Original Message-----
> > From: Mark Rivers [mailto:rivers@cars.uchicago.edu]
> > Sent: Tuesday, July 14, 2009 10:16 AM
> > To: Allison, Stephanie; Epics Questions
> > Subject: RE: When an external device does not provide termination on TCP ASCIIstream
> > replies
> >
> > Hi Stephanie,
> >
> > I think you should be fine.  Many TCP devices don't sent terminators,
> > unlike their serial counterparts.  In your st.cmd file you just don't
> > define an input or output EOS for that driver, and you don't put a
> > terminator in your protocol file.  The TCP driver does not loop waiting
> > for maxChars, it just reads the message.  TCP delivers "complete"
> > messages, so you will get the complete response, not just a partial
> > response.
> >
> > Mark
> >
> >
> > -----Original Message-----
> > From: tech-talk-bounces@aps.anl.gov
> > [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Allison, Stephanie
> > Sent: Tuesday, July 14, 2009 11:58 AM
> > To: Epics Questions
> > Subject: When an external device does not provide termination on TCP
> > ASCIIstream replies
> >
> > Hello,
> >
> > We're testing a Genesys power supply (provided by Lambda-TDK) to which
> > the vendor has added a TCP interface (I believe specifically by request
> > of EPICS sites).  Burkhard Kolb at GSI provided me the protocol file for
> > stream/asyn support for this type of device (thanks!).  However, the
> > firmware has changed recently and one change is to remove the terminator
> > from the reply strings.  Some replies are fixed-length so I can change
> > the protocol file for these (to use maxInput).  However some replies are
> > not fixed-length and I need to find support for those - I do not want to
> > rely on a timeout to know that the reply is finished.  The vendor has
> > suggested that (1) I assume the reply will never get fragmented and just
> > allocate 100 bytes and take whatever I get and (2) block on the receive
> > (which is not an option for an IOC).
> >
> > Does anybody have experience with such devices (TCP ASCII SCPI commands
> > that have no reply terminators and no fixed-length reply strings) and
> > can recommend a solution?
> >
> > Thank you,
> > Stephanie Allison
> > SLAC National Accelerator Lab
Hi Stephanie,
I just thought about a workaround...
Try this: append to all commands *OPC?, it should respond with "1".
(See section 7.8.10 of the technical manual)
Cheers, Burkhard
--
Dr. Burkhard Kolb
HADES
E-Mail: B.Kolb@gsi.de
Tel: +49-(6159)-71-2667 / Fax: +49-(6159)-71-2155

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