Experimental Physics and
Industrial Control System

Rod Nussbaumer <[email protected]> · Wed, 03 Sep 2014 07:29:52 -0700

David:

Your use case seems extremely typical for streamDevice applications, and

it's in use here in many many problem free instances. Can you confirm

that the behavior exists only with respect to this device, or is it

common to other types of devices and buses you're using, as well? What

kind of bus are you using? Does the problem manifest as a slow

degradation, or a sudden and spontaneous stoppage? Perhaps there is some

noise introducing a rogue character that is stopping the device, such as

XOFF in a serial device.

I assume your streamDevice device support is layered upon the asyn

package. I suggest enabling the asynTrace facility to allow you to

observe the data stream and the timing of the data transfers in your IOC

shell, especially as the problem period is anticipated. Using the asyn

record and the associated MEDM (any other display panels being

distributed for the asyn record???) displays makes this fairly convenient.

Rod Nussbaumer
Controls Group, TRIUMF
Vancouver, Canada

On 09/03/2014 06:55 AM, David Michel wrote:

Thanks Bob, I'm aware of being able to change the scan rate this way.
But longer scan rate is not really desirable. The typical task performed
by the device is only a couple of seconds, so long scan rate for status
updates would be close to useless.

David

---
Dr. David Michel
Address: 8 Viking Drive, Didcot, OX11 9RD, Oxfordshire
Mobile: 0789 670 98 01 - Home: 0123 581 46 93

On 3 September 2014 14:26, Dalesio, Leo <[email protected]
<mailto:[email protected]>> wrote:

    If you need a longer scan rate - you can modify menu.dbd. I think
    that the instructions in the Application Developer's Guide covers this.
    Bob

    ________________________________________
    From: [email protected]
    <mailto:[email protected]>
    [[email protected]
    <mailto:[email protected]>] on behalf of Mark Rivers
    [[email protected] <mailto:[email protected]>]
    Sent: Wednesday, September 03, 2014 8:08 AM
    To: David Michel; EPICS mailing list
    Subject: RE: Processing a record a in loop

    What is the maximum/typical time between when you send a query and
    receive a response?

    You should be able to set the timeout to a value just longer than
    the maximum and then you can process the record with any fixed rate
    (1 seconds, 10 seconds, etc.).  The record will be busy (PACT=1) if
    the next scan interval happens before the reply from the previous
    one.  So it will not keep sending query messages, it will wait for a
    reply before proceeding.

    What does your protocol file look like?  Is it a single query per
    response, etc.?

    Mark

    ________________________________
    From: [email protected]
    <mailto:[email protected]>
    [[email protected]
    <mailto:[email protected]>] on behalf of David Michel
    [[email protected] <mailto:[email protected]>]
    Sent: Wednesday, September 03, 2014 6:02 AM
    To: EPICS mailing list
    Subject: Processing a record a in loop

    Hi All,

    I'm using StreamDevice to talk to a custom device that doesn't
    support I/O interrupt so one has to keep sending commands to it to
    get status information.

    Problem is that after a while (~ couple of hours), the device's
    buffer fills up and doesn't reply anymore. Increasing the
    ReplyTimeOut improves things slightly, but the problem still
    eventually occurs.

    One potential solution would be to send the next command only once
    the previous one has returned in a loop (instead of using a set
    frequency).

    Making the record FWD link to itself doesn't seem to do it... I
    started something using purely database trickery with a FANOUT
    record set with a fixed SCAN field and disabling it depending on
    whether the streamdevice record has finished processing or not...
    but it's getting messy

    Is there an elegant way of doing this?

    David

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System