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EPICS ’ Stream ’ Device Support

This article explains the features and benefits of the EPICS Stream Device Support, which allows easy communication with temperature controllers and vacuum pumps using protocols like Serial (RS-232, RS485), Networked (TCP), and GPIB (IEEE-488). It provides an example implementation and highlights the advantages and challenges of using the Stream Device Support.

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EPICS ’ Stream ’ Device Support

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  1. EPICS’Stream’Device Support Kay Kasemir ORNL/SNS kasemirk@ornl.gov Feb. 2013

  2. “Stream” Type Protocols Example Devices: • Temperature controllers: Lakeshore, Omega, … • Vacuum pumps: Varian, … • Serial (RS-232, RS485), Networked (TCP), GPIB (IEEE-488) • Text-based • Command/Response What is the current temperature on channel A?“KRDG? A\n” “+077.350E+0\n”It’s about 80 Kelvin!

  3. Pro/Cons • Seems easy • Human-readable • Testable with Hyperterm, minicom, telnet • Create Visual Basic, LabVIEW, … demo in no time • But beware! • Speed and Terminators (CR, LF, CR/LF, …) can magically change • Was set to something, then device power-cycled … • Must handle timeouts • Don’t just hang! • Must handle errors • Don’t read “MODEL 340” as 340 Kelvin

  4. The EPICS ‘Stream’ Device Idea Recordrecord(ai, "Temp:B"){ field(DTYP,"stream") field(INP, "@demo.protogetTempATC1") field(SCAN,"5 second")} Protocol File“demo.proto”Terminator = CR;getTempA{ out "KRDG? A"; in "%f";} IOC st.cmddrvAsynIPPortConfigure ("TC1", "192.168.164.10:23")

  5. What ‘Stream Device’ does for you • Connect to device • Re-connect after disconnects • Allow many records to communicate via one connection • Threading, queuing, … • Handle timeouts, errors • Put records into ‘alarm’ state • Debug options • Log every byte sent/received

  6. NetCat Example Using NetCat, we pretend to be a simple device. • IOC with Stream Device will ask:“B?” • We reply either • with valid reply to request for B:“B 42.13” • Invalid reply:“42.13”, “get lost”, … • Not at all, which should be treated as timeout, • a shutdown of the network connection.

  7. Full Example: Adding support to IOC • configure/RELEASE:SUPPORT=/home/controls/epics/R3.14.12.2/supportASYN=$(SUPPORT)/asynSTREAM=$(SUPPORT)/StreamDevice • demoApp/src/Makefiledemo_DBD += stream.dbddemo_DBD += asyn.dbddemo_DBD += drvAsynIPPort.dbddemo_LIBS += asyndemo_LIBS += stream

  8. EPICS Database demoApp/Db/demo.db record(ai, "B"){ field (DTYP, "stream") field (INP, "@demo.proto getB NC") field (SCAN, "5 second")} record(ao, "current"){ field (DTYP, "stream") field (OUT, "@demo.proto setCurrent NC") field (EGU, "A") field (PREC, "2") field (DRVL, "0") field (DRVH, "60") field (LOPR, "0") field (HOPR, "60“} record(ai, "A"){ field (DTYP, "stream") field (INP, "@demo.proto getA NC") field (SCAN, "I/O Intr")}

  9. Protocol File # Example with initialization,# otherwise only writes when processedsetCurrent{ out "CURRENT %.2f"; @init { out "CURRENT?"; in "CURRENT %f A"; }} # Used with SCAN, "I/O Intr":# Reacts to "A 5" at any timegetA{ PollPeriod = 50; in "A %f";} iocBoot/iocdemo/demo.proto Terminator = CR LF;InTerminator = LF;ReplyTimeout = 10000;ReadTimeout = 10000; # Used with SCAN “… second”:# Prompts, then expects "B 5"getB{ out "B?"; in "B %f“;}

  10. IOC Startup File iocBook/iocdemo/st.cmd epicsEnvSet ("STREAM_PROTOCOL_PATH", ".") drvAsynIPPortConfigure ("NC", "127.0.0.1:6543") # ASYN_TRACE_ERROR 0x0001# ASYN_TRACEIO_DEVICE 0x0002# ASYN_TRACEIO_FILTER 0x0004# ASYN_TRACEIO_DRIVER 0x0008# ASYN_TRACE_FLOW 0x0010# ASYN_TRACEIO_NODATA 0x0000# ASYN_TRACEIO_ASCII 0x0001# ASYN_TRACEIO_ESCAPE 0x0002# ASYN_TRACEIO_HEX 0x0004# Log some asyn info and in/out textsasynSetTraceMask("NC", 0, 4)asynSetTraceIOMask("NC", 0, 6) dbLoadRecords("db/stream.db","user=fred")

  11. Example Session • IOC…write 4B?\r\n…read 5B 17\n… got "34" where "B " was expected… No reply from device within 10000 ms • NetCatnc –l 127.0.0.1 6543B?B 17B?B 18B?B 3.14B?34B?

  12. Stream Device… • Allows you to concentrate on the protocol • Handles the rest • Connection • Threads • Parse results • Update record’s valueand alarm state “demo.proto”Terminator = CR;getTempA{ out "KRDG? A"; in "%f";}

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