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Subject: SNC Sequencer 2.2 not working when reading remote IOC variables? (no attachments)
From: "keith.thorne" <kthorne@ligo-la.caltech.edu>
To: EPICS mailing list <tech-talk@aps.anl.gov>
Date: Wed, 23 Aug 2017 12:36:50 -0500
Dear EPICS team

— removed attachments to get this out. --

	At LIGO, we use the EPICS SNC Sequencer to provide communication between our real-time code and the user variables, expressed in an EPICS IOC.
We use auto-generated SNC files to build and compile our EPICS executable.

We had been using SNC version 2.1 and all was working (even with latest 2.1 revision).  However, if we use SNC version 2.2, we are not able to get data from EPICS PVs on IOCs on other computers.

Our existing SNC code (elided for relevancy) is

ss monitorFilt{
state init
{
 when() {
...
pvGet(evar_X2_CDS_EXTERNAL_TEST);
...
 } state daqInit
}
state daqInit
{
 when()
   {
...
pvGet(evar_X2_CDS_EXTERNAL_TEST);
evar_X2_CDS_EXTERNAL_TEST_ERR = pvConnected(evar_X2_CDS_EXTERNAL_TEST);
...
  } state daqProcess
}   

This gets converted to (again elided )
# line 4369 "x2hpiboot.i"
			seq_pvGetTmo(seqg_env, 552/*evar_X2_CDS_EXTERNAL_TEST*/, DEFAULT, DEFAULT_TIMEOUT);
...			
# line 6196 "x2hpiboot.i"
			seq_pvGetTmo(seqg_env, 552/*evar_X2_CDS_EXTERNAL_TEST*/, DEFAULT, DEFAULT_TIMEOUT);

# line 6198 "x2hpiboot.i"
			evar_X2_CDS_EXTERNAL_TEST_ERR = seq_pvConnected(seqg_env, 552/*evar_X2_CDS_EXTERNAL_TEST*/);

However, when we run it, we get X2_CDS_EXTERNAL_TEST_ERR become 1, but we never get any updates to the variable, but continuous log messages like

sevr=major pvGet(ss monitorFilt, var evar_X2_CDS_EXTERNAL_TEST, pv X2:CDS-EXTERNAL_TEST): user error (there is already a pvGet pending for this channel/state set combination)
sevr=major pvGet(ss monitorFilt, var evar_X2_CDS_EXTERNAL_TEST, pv X2:CDS-EXTERNAL_TEST): user error (there is already a pvGet pending for this channel/state set combination)
sevr=major pvGet(ss monitorFilt, var evar_X2_CDS_EXTERNAL_TEST, pv X2:CDS-EXTERNAL_TEST): user error (there is already a pvGet pending for this channel/state set combination)

I had thought the change to seq_pvGetTmo() merely implemented the existing behavior, but perhaps I am wrong?

How should we code thing that monitor external IOC variables for changes?

	Sincerely
		Keith Thorne

------
Keith Thorne <kthorne@ligo-la.caltech.edu>
CDS Software Engineer
LIGO Livingston Laboratory
Livingston, LA 70754
Phone: (225)686-3168 Fax: (225)686-7189


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