LabVIEW Channel Access Implementaion

1
LabVIEW Channel Access Implementaion

• Alexander Zhukov
• SNS

2
SNS diagnostics

• We have 200 devices running on Windows-based
  IOCs
• Beam Current Monitors
• Beam Position Monitors
• Wire Scanners
• Laser Wire
• Timing fanouts
• and more
• The hardware is controlled by LabVIEW (6.1 8.5)

3
EPICS shared memory interface
LabVIEW Application (Wire Scanner, BPM,etc)
ReadData() WaitForInterrupt() GetIndexByName()
Channel Access
CreateDBEntry()
IOC (database, CA)
Shared Memory DLL
WriteData() SetInterrupt()
DBD and DBD files
ICALEPCS talk by W.Blokland, D.Thompson
4
What is good and not so good?

• Good
• You have full IOC and everything that comes with
  it (including record processing)
• All EPICS tools will work by default
• Not so good
• Can we move on Linux (probably yes, but more
  effort needed)?
• cRIO (could be done as we saw, but not easy)
• Need to support 2 infrastructure for EPICS IOC
  and for LabVIEW program (we can work around, but
  the bundle is still a little bit ugly)
• Deployment is complicated one has to make sure
  that 2 different parts (and processes) are
  behaving

5
What do we actually need?

• Not an IOC but CA server (since IOC is used for
  talking CA only)
• To Host about 2000 PVs
• To to connect to 50 CA clients
• To provide 10Mbit/s of data transfer
• To be compatible with all platforms LabVIEW runs
  on (Windows,Linux, MAC, compactRIO, LabVIEW
  RealTime)
• We never use record processing

Why not implement the CA protocol in LabVIEW? Is
it possible? Is it fast? Will it really be
compile once, run everywhere?
6
Pilot project

• Assess possible CA implementation in LabVIEW
• No Repeater
• No beacons (do we really need them btw?)
• Support UDP channel search
• Support two CA types (FLOAT and LONG)
• Support DBR_STS and DBR_TIME
• Support put/get/monitor

7
Server Structure

• Launch UDP listener (for search requests)
• Launch TCP listener (for new VC connections)
• Launch several threads for communication
• Launch one (or several) threads for message
  processing
• Three queues responsible for data transfer and
  data locking
• VC can be in either processing state or in
  communication state
• Records are guarded differently

8
Demo program structure
Get value from CA
Create PV
Put initial value (and publish to CA)
Publish Array
9
Linux running CA server
10
Mac OS running CA server (Blokland)
CA Server running on Macintosh, display through
CAML in Safari
11
NI cRIO running CA server (Blokland)
12
TODO

• Full CA types support
• Develop simple API (that will be applicable to
  both local PVs and remote PVs, connected through
  CA client) and FREEZE them
• Support all possible type conversion
• Error management (external error logger?)
• Performance improvement (we are optimistic here
  since in works OK for our needs with no
  optmisation already)
• CA client!!!

13
Summary

• It worked!
• We are able to satisfy our requirements
• We were able to get 160Mbit/s (running on PC)
• We will proceed and try to have full working
  version at mid-fall