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Subject: pyepics callback
From: Alfio Rizzo via Tech-talk <tech-talk@aps.anl.gov>
To: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Mon, 9 Sep 2019 13:24:39 +0000

Hi

I made a simple python script to get the updated value of my PV

with a simple callback function :

 

import epics

import time

 

def onChanges(**kw):

    print ('PV Changed! ', kw["pvname"], kw["value"], kw["units"], time.ctime())

 

mypv = epics.PV("TCU6:RF")

mypv.add_callback(onChanges)

 

while True:

    pass

   

 

The issue is that the unit is shown as None even if it defined in the .db

 

PV Changed!  TCU6:RF -39.69 None Mon Sep  9 15:03:58 2019

PV Changed!  TCU6:RF -39.73 None Mon Sep  9 15:03:59 2019

PV Changed!  TCU6:RF -39.71 None Mon Sep  9 15:04:00 2019

PV Changed!  TCU6:RF -39.7 None Mon Sep  9 15:04:01 2019

PV Changed!  TCU6:RF -39.67 None Mon Sep  9 15:04:02 2019

 

 

But if I add this line on the script before to add the callback

 

……

mypv.units

mypv.add_callback(onChanges)

……

 

Then when I restart the script it shows the unit correctly

 

 

PV Changed!  TCU6:RF -39.79 dBm Mon Sep  9 15:04:31 2019

PV Changed!  TCU6:RF -39.71 dBm Mon Sep  9 15:04:32 2019

PV Changed!  TCU6:RF -39.69 dBm Mon Sep  9 15:04:33 2019

 

 

Is this a bug/feature or I am doing something wrong ?

 

Thanks

Best

 

 

 

PhD Alfio Rizzo

Control System Integrator

Integrated Control Systems Division

European Spallation Source ERIC

 

Telephone: +46(0)721792342

Mail Address: P.O Box 176, SE 221 00 Lund, Sweden

Visiting address: Odarslövsvägen 113, Lund

 

https://europeanspallationsource.se/

 

essLogo

 


Replies:
Re: pyepics callback Eric Norum via Tech-talk
Re: pyepics callback Matt Newville via Tech-talk

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