Experimental Physics and
Industrial Control System

Hi,

On Mon, Sep 19, 2022 at 10:57 AM LE-DANIEL Erwann <erwann.le-daniel at alstomgroup.com> wrote:

OK.  Then, I'm less sure about what is going on.  Creating multiple instances of a PV in a loop would be an odd thing to do, though it will not create completely new connections to the CA Channel: `epics.ca._cache` should only have one Channel in it, though it will retain a large number of callbacks that are no longer accessible.  I don't know if there is a limit on the number of PVs that can be created - your script runs to at least 3000 times for me, though I did not test with raspberry pi.

But: For sure, creating a PV and then fetching its value repeatedly is recommended:

p = epics.PV(‘TL_AN_Input’)

while True:

               val = p.get()

               print (val)

               time.sleep(0.1)

There is also `epics.get_pv` which will get a cached PV or create one if needed:

while True:

               p = epics.get_(‘TL_AN_Input’)

               val = p.get()

               print (val)

               time.sleep(0.1)

this will prevent the creation of thousands of useless callbacks.

--Matt