Experimental Physics and
Industrial Control System

Hi, Xiaoqiang et. al.  I'm seeing some behavior in pcaspy 0.7.0 that I'm
not understanding, and I'm hoping you can help me figure out what's
going on.

I have a trivial test pcaspy IOC (code attached) serving a single
channel "TEST:A".  After starting the IOC I run camonitor on the
channel:

$ camonitor TEST:A
TEST:A                         2017-12-27 19:15:42.991145 0

If I then put the *same* initial value into the channel...

$ caput TEST:A 0
Old : TEST:A                         0
New : TEST:A                         0
$

...I see an update:

guard-test> camonitor TEST:A
TEST:A                         2017-12-27 19:15:42.991145 0  
TEST:A                         2017-12-27 19:15:50.661466 0  

Additional puts with the same value show no more spurious updates.  So
this only happens immediately after initialization.

This is contrary to the behavior that I now expect, whereby there would
never be external updates if the value was not changing.  Can you help
me understand what's going on?

Basically I'm looking for the best way to get consistent behavior out of
the pcaspy driver, either where puts always show updates even if the
value is the same, or that puts of the current value do not ever show
updates.  How can I achieve this?

Thanks in advance for any help.

jamie.

#!/usr/bin/env python

import sys
import pcaspy

prefix = 'TEST:'
pvdb = {
    'A': {
        'prec': 0
    },
}

class DummyDriver(pcaspy.Driver):
    pass

server = pcaspy.SimpleServer()
server.createPV(prefix, pvdb)
driver = DummyDriver()

for k in pvdb:
    driver.setParamStatus(k, pcaspy.Severity.NO_ALARM, pcaspy.Severity.NO_ALARM)
driver.updatePVs()

while True:
    server.process(0.1)

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Replies:

Re: same value updates after initialization in pcaspy 0.7.0 Jameson Graef Rollins

Re: same value updates after initialization in pcaspy 0.7.0 Jameson Graef Rollins

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