Experimental Physics and
Industrial Control System

Burkhard Kolb <[email protected]> · Wed, 15 Jul 2009 11:09:27 +0200

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:[email protected]]
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: [email protected]
[mailto:[email protected]] 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
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System