ActiveX CA ServerClient Update

1
ActiveX CA Server/Client Update

• Nov. 2000
• Kay-Uwe Kasemir, LANL

2
ActiveX CA Server/Client

• http//lansce.lanl.gov/lansce8/epics/PC
• Does Andrew really want this link?
• Can be used with many Win32 programs Visual
  Basic, LabVIEW, Delphi,
• Reality Used with LabVIEW
• LEDA 1.5y experience, 10 PCs, 2 .. 400(!)PVs
  each
• Other Labs gt25 requests, mostly for the server,
  though often unclear (non-EPICS users)
• Requests for new options
• string support
• allow passing value, time to server

3
LANL Experience

• Terrific for small systems
• Signal generator, GPIB, new PC 2 hours!
• No need for vxWorks, IOC, boot host, display
  computer
• Faster initial development cycle no recompile
  reboot,
• (until turned into distributed system)
• Easier to learn(?)
  vs.

4
LabVIEW Issues

• Visual programming is limited
• image gets too big, wires tangled
• no ASCII import/export
• no real CVS support, no comparable NI tool
• no script-generated code from signal list, RDB,
  Capfast, ...
• what you see is all you get
• IOCs scanning mechanisms have to be
  re-implemented with fundamental
  instructions(loops, delays, )

5
LabVIEW Issues

• Complex logic, many PVs hard to maintain
• sequences show only one step at a time
• array handling in for-loopsnecessary for bigger
  systems but misleading(auto-indexing fails for
  different array sizes)

6
Performance Looks OK

• 450Mhz PC 0.3ms, send value from LabVIEW to
  ActiveX CA Server
• 900Mhz 0.14ms
• Main factor COM
• (10 PVs _at_ 10, 100, 500 Hz on 450Mhz Pentium II)

7
LabVIEW Polling

• CA put ltnew valuegt into PV on ActiveX CA
  Server...
• ActiveX Event is sent with ltnew valuegt,receiver
  like LabVIEW has to decide whether to serve the
  new value, a modified value or keep the old one.
• VisualBasic can handle events async.,LabVIEW can
  only WaitForEvent
• User waits for responseuntil LabVIEWsmain loop
  comes aroundto service the PV changes
• LabVIEW offers threads semaphores, but
  evenmany Nat.Inst. VIsare incompatible.

Main code in here!
8
LabVIEW/PC Issues

• No remote login into PC
• LabVIEW 5.1 sometimes crashes during setup of
  ActiveX connection(runs fine once this succeeds)
• ActiveX Events
• didnt work before LabVIEW 5.1
• 5.1 still didnt work originally, it took
  bulletproof examples for NI support to
  acknowledge their problem and provide patch, now
  available from National Instruments web site
• memory leak in 5.1, supposed to be gone in 6i
  (not tested)
• Time stamps not synchronized with other EPICS
  IOCs
• could be called an EPICS fault because IOCs use
  proprietary protocol

9
Conclusion (still)

• Win32-Program (with not too much) data worth
  serving, e.g. LabVIEW

ActiveX CA Server