How to use GPIB ports with linux-gpib and StreamDevice

This document evolved from a reply I sent to tech-talk to someone who was struggling with the setup of his GPIB device using devGpib.

Introduction

The following instructions explain the setup of an EPICS softIOC to talk to a GPIB device on Linux.

The instructions are based on Debian Linux, but should be easily adaptable to other flavors of Linux.

Prerequisites

You need linux-gpib, EPICS base, asyn, and StreamDevice.

linux-gpib installation

On Debian, you can just do

     apt-get install gpib-modules-source module-assistant
     module-assistant auto-install gpib-modules-source

to build and install the kernel modules of the linux-gpib driver for your kernel. Similarly, by issuing

     apt-get install libgpib0 libgpib0-dev libgpib-bin

you can install the user space part of linux-gpib.

On other distributions, check for the availability of linux-gpib packages. You can always resort to compiling linux-gpib youself. Refer to the linux-gpib documentation[1] for this.

Once you have linux-gpib installed, it's time to configure your interface board. Assuming you have a single GPIB interface board in your machine, you'll need to

• figure out the board type, i.e. find out what low-level driver from linux-gpib does support you board, e.g. ines_pci, and

• give the interface board an arbitrary name, e.g. L0. You'll need to use this name as the first parameter to the GpibBoardDriverConfig command in the st.cmd of your softIOC later on. There seems to be a convention for the name to start with "L".

To be able to use the interface board as /dev/gpib0, put something like

     interface {
             minor = 0       /* board index, minor = 0 is /dev/gpib0 */
             board_type = "ines_pci" /* type of interface board being used */
             name = "L0"     /* board name */
             pad = 0         /* primary address of interface */
             sad = 0         /* secondary address of interface */
             timeout = T3s   /* timeout for commands */
             eos = 0x0a      /* EOS Byte, 0xa is LF and 0xd is CR */
             set-reos = yes  /* Terminate read if EOS */
             set-bin = no    /* Compare EOS 8-bit */
             set-xeos = no   /* Assert EOI whenever EOS byte is sent */
             set-eot = yes   /* Assert EOI with last byte on writes */
             master = yes    /* interface board is system controller */
     }

in /etc/gpib_conf, load the kernel driver for your board

     modprobe ines_pci

and finally run

     gpib_config

Verify connection to GPIB board

Verify you can talk to the board using ibtest:

     sheim@txm1:~$ ibtest
     Do you wish to open a (d)evice or an interface (b)oard?
             (you probably want to open a device): b
     enter name of interface board (or device) you wish to open: L0
     trying to open board named 'L0'
     You can:
             w(a)it for an event
             write (c)ommand bytes to bus (system controller only)
             send (d)evice clear (device only)
             change remote (e)nable line (system controller only)
             (g)o to standby (release ATN line, system controller only)
             send (i)nterface clear (system controller only)
             ta(k)e control (assert ATN line, system controller only)
             get bus (l)ine status (board only)
             go to local (m)ode
             change end (o)f transmission configuration
             (q)uit
             (r)ead string
             perform (s)erial poll (device only)
             change (t)imeout on io operations
             request ser(v)ice (board only)
             (w)rite data string
     : l
     DAV off
     NDAC on
     NRFD off
     IFC off
     REN on
     SRQ off
     ATN off
     EOI on
     gpib status is:
     ibsta = 0x164  < CMPL REM CIC LACS >
     iberr= 0

     ibcnt = 0
     You can:
             w(a)it for an event
             write (c)ommand bytes to bus (system controller only)
             send (d)evice clear (device only)
             change remote (e)nable line (system controller only)
             (g)o to standby (release ATN line, system controller only)
             send (i)nterface clear (system controller only)
             ta(k)e control (assert ATN line, system controller only)
             get bus (l)ine status (board only)
             go to local (m)ode
             change end (o)f transmission configuration
             (q)uit
             (r)ead string
             perform (s)erial poll (device only)
             change (t)imeout on io operations
             request ser(v)ice (board only)
             (w)rite data string
     : q
     sheim@txm1:~$

Verify connection to the GPIB device

Assuming your device has GPIB address 2 and will answer to the command ":FETC?", test it with ibtest like this:

     sheim@brixen:~$ ibtest
     Do you wish to open a (d)evice or an interface (b)oard?
             (you probably want to open a device): d
     enter primary gpib address for device you wish to open [0-30]: 2
     trying to open pad = 2 on /dev/gpib0 ...
     You can:
             w(a)it for an event
             write (c)ommand bytes to bus (system controller only)
             send (d)evice clear (device only)
             change remote (e)nable line (system controller only)
             (g)o to standby (release ATN line, system controller only)
             send (i)nterface clear (system controller only)
             ta(k)e control (assert ATN line, system controller only)
             get bus (l)ine status (board only)
             go to local (m)ode
             change end (o)f transmission configuration
             (q)uit
             (r)ead string
             perform (s)erial poll (device only)
             change (t)imeout on io operations
             request ser(v)ice (board only)
             (w)rite data string
     : w
     enter a string to send to your device: :FETC?
     sending string: :FETC?

     gpib status is:
     ibsta = 0x2100  < END CMPL >
     iberr= 0

     ibcnt = 7
     You can:
             w(a)it for an event
             write (c)ommand bytes to bus (system controller only)
             send (d)evice clear (device only)
             change remote (e)nable line (system controller only)
             (g)o to standby (release ATN line, system controller only)
             send (i)nterface clear (system controller only)
             ta(k)e control (assert ATN line, system controller only)
             get bus (l)ine status (board only)
             go to local (m)ode
             change end (o)f transmission configuration
             (q)uit
             (r)ead string
             perform (s)erial poll (device only)
             change (t)imeout on io operations
             request ser(v)ice (board only)
             (w)rite data string
     : r
     enter maximum number of bytes to read [1024]:
     trying to read 1024 bytes from device...
     received string: '-000.0003E-12ADC
     '
     Number of bytes read: 17
     gpib status is:
     ibsta = 0x2100  < END CMPL >
     iberr= 0

     ibcnt = 17
     You can:
             w(a)it for an event
             write (c)ommand bytes to bus (system controller only)
             send (d)evice clear (device only)
             change remote (e)nable line (system controller only)
             (g)o to standby (release ATN line, system controller only)
             send (i)nterface clear (system controller only)
             ta(k)e control (assert ATN line, system controller only)
             get bus (l)ine status (board only)
             go to local (m)ode
             change end (o)f transmission configuration
             (q)uit
             (r)ead string
             perform (s)erial poll (device only)
             change (t)imeout on io operations
             request ser(v)ice (board only)
             (w)rite data string
     : q
     sheim@brixen:~$

If communication with the device works using ibtest, the setup of the softIOC is trivial if you stick to the 7-step recipe in section 3.

EPICS installation

Since I maintain Debian packages for EPICS base, all support modules and all extensions I use, here I just do:

     apt-get install epics-base epics-support-asyn epics-support-streamdevice

Until I find the time to publish my Debian EPICS archive (sid, lenny, etch, sarge and several Ubuntu versions available), or if you are using a different distribution anyway, you'll have to stick to compiling and installing EPICS base, asyn and StreamDevice yourself.

The softIOC

Now it's time to set up the actual softIOC.

STEP 1: Create GPIB application

In a fresh and clean directory, do

     makeBaseApp.pl -t example gpib
     makeBaseApp.pl -t example -i -a linux-x86 -p gpib gpib

STEP 2: Use asyn and StreamDevice support

Append to configure/RELEASE

     ASYN=/opt/epics/support/asyn
     STREAMS=/opt/epics/support/streamdevice

Make sure you have asyn and StreamDevice installed and supply the correct paths to your EPICS support directories.

STEP 3: Create a protocol file

Create a protocol file

     gpibApp/Db/yourdev.proto

like this:

     === gpibApp/Db/yourdev.proto ===
     Terminator = CR LF;

     getCurrentStep {
             out ":CURR:STEP?";
             in "%f";
     }

     setCurrentStep {
             out ":CURR:STEP %f";
     }
     ================================

You might want to consult the SCPI command reference for your device and 
implement whatever part of the protocol you may need.

STEP 4: Create a database

Create a database

     gpibApp/Db/yourdev.db

matching the protocol from STEP 3 like this:

     === gpibApp/Db/yourdev.db ===
     record (ai, "$(P)currentStep")
     {
             field (SCAN, "Passive")
             field (DTYP, "stream")
             field (INP,  "@yourdev.proto getCurrentStep $(PORT) $(ADDR)")
     }

     record (ao, "$(P)setCurrentStep")
     {
             field (SCAN, "Passive")
             field (DTYP, "stream")
             field (OUT,  "@yourdev.proto setCurrentStep $(PORT) $(ADDR)")
     }
     =============================

In order to register your database with the build system, add the line

     DB += yourdev.db

in the middle of

     gpibApp/Db/Makefile.

STEP 5: Adapt application Makefile

Have

     gpibApp/src/Makefile

read:

     === gpibApp/src/Makefile ===
     TOP=../..
     include $(TOP)/configure/CONFIG

     # build an ioc application
     PROD_IOC = gpib
     PROD_LIBS += asyn
     PROD_LIBS += stream

     # gpib.dbd will be created and installed
     DBD += gpib.dbd

     # gpib.dbd will be made up from these files:
     gpib_DBD += base.dbd
     gpib_DBD += asyn.dbd
     gpib_DBD += drvAsynIPPort.dbd
     gpib_DBD += drvAsynSerialPort.dbd
     gpib_DBD += drvLinuxGpib.dbd
     gpib_DBD += stream.dbd

     # softIOC house-keeping
     gpib_SRCS += gpib_registerRecordDeviceDriver.cpp
     gpib_SRCS_DEFAULT += gpibMain.cpp
     gpib_LIBS += $(EPICS_BASE_IOC_LIBS)

     include $(TOP)/configure/RULES
     ============================

STEP 6: Create an IOC startup script

Have the IOC's st.cmd look like this:

     === iocBoot/iocgpib/st.cmd ===
     #!../../bin/linux-x86/gpib

     < envPaths
     epicsEnvSet(STREAM_PROTOCOL_PATH, "../../gpibApp/Db")
     cd ${TOP}

     ## 1 Register all support components
     dbLoadDatabase("dbd/gpib.dbd")
     gpib_registerRecordDeviceDriver(pdbbase)

     ## 2 Configure your asynPorts
     # 2a GPIB: portname, autoConnect, boardId, timeout, 5th_arg
     GpibBoardDriverConfig("L0", "1", "0", "3", "0")
     # Note1: The portname has to match the interface name of your board
     #        from /etc/gpib.conf!
     # Note2: boardId is the GPIB address *of your GPIB controller board*.
     #        The GPIB address of the _device_ itself is supplied to
     #        dbLoadRecords under step 3 below.
     # 2b TCP/IP socket: IPaddress:port
     #drvAsynIPPortConfigure("IPPORT","192.168.0.1:6789")
     # 2c Serial: "COM1", 9600 bps, 8N1, flow contr.: XON/XOFF
     #drvAsynSerialPortConfigure ("SERIALPORT", "/dev/ttyS0", 0, 0, 0)
     #asynSetOption ("SERIALPORT", 0, "baud", "9600")
     #asynSetOption ("SERIALPORT", 0, "bits", "8")
     #asynSetOption ("SERIALPORT", 0, "parity", "none")
     #asynSetOption ("SERIALPORT", 0, "stop", "1")
     #asynSetOption ("SERIALPORT", 0, "clocal", "Y")
     #asynSetOption ("SERIALPORT", 0, "crtscts", "N")
     # 2d vxi11: ...

     ## 3 Load record instances
     # Make sure you have your device's GPIB address right!
     dbLoadRecords("db/yourdev.db", "P=${IOC}:,PORT=L0,ADDR=2")

     cd ${TOP}/iocBoot/${IOC}
     iocInit()

     ==============================

STEP 7: Build and test IOC

Finally run

     make
     cd iocBoot/iocgpib
     chmod +x st.cmd
     ./st.cmd

to get something like

Starting iocInit
############################################################################
## EPICS R3.14.9-3 $R3-14-9$ $2007/02/05 16:31:45$
## EPICS Base built Jan 17 2008
############################################################################
iocInit: All initialization complete
epics> dbl
iocgpib:currentStep
iocgpib:setCurrentStep
epics> dbpf iocgpib:currentStep.PROC 1
DBR_UCHAR: 1 0x1
epics> 2008/01/18 05:17:01.124 L0 addr 2 : device timed out.
2008/01/18 05:17:01.125 iocgpib:currentStep: Timeout after reading 17 
bytes "-000.0007E-12ADC<0a>"
2008/01/18 05:17:01.125 iocgpib:currentStep: 4 bytes surplus input "ADC<0a>"
2008/01/18 05:17:01.125 iocgpib:currentStep: after 13 bytes: "-000.0007E-12"
epics> 

The response here comes from my Keithley 6517A sitting at address 2 and doesn't exactly match what we expect. In fact, not even our EOS terminator setting is correct, that's why the device timeouts. With the exemplary debugging information provided by StreamDevice at hand, it is a joy to incrementally fix the "in" clauses in yourdev.proto to match what the device _really_ sends. Here, the getCurrentStep protocol would need to be changed to

     Terminator = LF;
     getCurrentStep {
             out ":CURR:STEP?";
             in "%fADC";
     }

You can reload the protocol in the iocsh via "streamReload", either for one or for all records. Without rebooting the IOC. Without any recompilation.

Once the protocol works, do a dbpf/caput iocgpib:currentStep.SCAN ".1 second" to have your IOC poll the device regularly. Or even better, have the device send out readings on its own if possible and parse them in a protocol run from an record with .SCAN="I/O Intr".

StreamDevice offers a broad range of so called format converters (the "%f" in the in clause of the getCurrentStep protocol in yourdev.proto). There's even a regular expression string converter that you can use to parse your favorite stock quote from a web page into an EPICS variable.

-Stefan Heim <[email protected]>, Jan 18 2008