GPIB::llp - Perl-GPIB interface for Linux Lab Project GPIB device drivers

GPIB documentation Contained in the GPIB distribution.

Index

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NAME

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GPIB::llp - Perl-GPIB interface for Linux Lab Project GPIB device drivers

SYNOPSIS

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  use GPIB;

  $g = GPIB->new("name");
  $g->ibwrt('*IDN?');
  print $g->ibrd(1024);

DESCRIPTION

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GPIB::llp is an interface module for accessing Linux Lab Project GPIB device drivers. This XS module builds and has been tested on Linux using an NI PCIIA card. This module is normally not used directly, but called by GPIB.pm according to an entry in /etc/pgpib.conf or by calling GPIB->new() and passing GPIB::llp as the first parameter.

A typical /etc/pgpib.conf entry for using GPIB::llp is shown below:

  # name              /etc/pgpib.conf name
  K2002   GPIB::llp   K2002

The device is used in a Perl program as follows:

  use GPIB;

  $g = GPIB->new("K2002");

In the above example, the K2002 entry indicates that GPIB::llp interface will use the string K2002 in a call to ibfind() to locate the device. Unlike GPIB::ni, GPIB:llp uses the configuration information maintained by the LLP driver in /etc/gpib.conf (not /etc/pgpib.conf) for accessing the device. The LLP library does not provide an ibdev() call so it's not possible to provide the same specification control available to GPIB::ni.

The LLP library is missing a few other standard GPIB calls in addtion to ibdev(). The following calls are stubbed out to do nothing:

        ibdev
        ibask
        ibbna
        ibist
        ibln
        ibpct
        ibppc
        ibrdf
        ibrsc
        ibstop
        ibwrtf

There is some odd behaviour particular to the GPIB::llp interface: If a call to ibrd() is made with a long timeout, the system will pretty much hang waiting on the read to complete or timeout. The driver seems to take full control of the system.

An ibwrt() or ibrd() seems to be limited to about 64k bytes. I cannot find a precise answer, but larger reads fail. Keep I/O operations using GPIB::llp small.

The module seems to have some unusual behaviour with CPUs faster than 300MHz, I haven't narrowed this down.

I think there is an off-by-one error in $g->ibrd(). Sometimes I get the last character in the returned string twice.

This interface is not tested as well as the National Instruments interface (GPIB::ni). I use GPIB::ni most of the time.

CREDIT

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This module is loosely based on a Perl XS module Steve Tell at UNC (tell@cs.unc.edu) wrote for accessing GPIB devices from Perl.

AUTHOR

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Jeff Mock, jeff@mock.com

SEE ALSO

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perl(1), GPIB(3), GPIB::ni(3), GPIB::hpserial(3), GPIB::rmt(3), Linux Lab Project http://www.llp.fu-berlin.de/

GPIB documentation Contained in the GPIB distribution. 
package GPIB::llp;

use strict;
use Carp;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);

require Exporter;
require DynaLoader;
require AutoLoader;

@ISA = qw(Exporter DynaLoader);

@EXPORT = qw();
@EXPORT_OK = qw();

$VERSION = '0.30';

sub AUTOLOAD {
    # This AUTOLOAD is used to 'autoload' constants from the constant()
    # XS function.  If a constant is not found then control is passed
    # to the AUTOLOAD in AutoLoader.

    my $constname;
    ($constname = $AUTOLOAD) =~ s/.*:://;
    croak "& not defined" if $constname eq 'constant';
    my $val = constant($constname, @_ ? $_[0] : 0);
    if ($! != 0) {
	if ($! =~ /Invalid/) {
	    $AutoLoader::AUTOLOAD = $AUTOLOAD;
	    goto &AutoLoader::AUTOLOAD;
	}
	else {
		croak "Your vendor has not defined GPIB macro $constname";
	}
    }
    # *$AUTOLOAD = sub () { $val };
    eval "sub $AUTOLOAD { $val }";
    goto &$AUTOLOAD;
}

bootstrap GPIB::llp $VERSION;

sub new {
    my $pkg = shift; 
    my $g = undef;
    my $i;

    if (@_ == 1) {
        $g = ibfind($_[0]);
    } elsif (@_ == 6) {
        $g = ibdev(@_);
    } else {
        die("Bad parameter list to GPIB::llp::new($pkg @_)");
    }

    # Larry thinks new() should die on failure...
    if ($g->ibsta & GPIB->ERR) {
        my  @c = caller;
        die "GPIB::llp::new(@_) failed\n    ";
    }
    bless $g, $pkg;
    return $g;
}

# LLP is missing some standard GPIB calls.  They are stubbed out
# to tacitly do nothing here.  Maybe they should be noisy...
#
sub ibdev { -1; }
sub ibask { 0; }
sub ibbna { 0; }
sub ibist { 0; }
sub ibln { 1; }    #  Hmm, we need this
sub ibpct { 0; }
sub ibppc { 0; }
sub ibrdf { 0; }
sub ibrsc { 0; }
sub ibstop { 0; }
sub ibwrtf { 0; }


1;
__END__
# Below is the stub of documentation for your module. You better edit it!