/ 
GPIB_0_30
River stage zero No dependents
/ GPIB::llp

NAME

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

SYNOPSIS

use GPIB;

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

DESCRIPTION

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

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

Jeff Mock, jeff@mock.com

SEE ALSO

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