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Many of these systems are
created with VXI- or PXI-
based hardware and controlled
with either an embedded PC
or standalone PC connected
through an interface card and
cable. LXI solves four key prob-
lems developers would typically
face under these methods:
• Interface: Rather than an
MXI or GPIB interface,
LXI uses Ethernet,
eliminating the need to
install an additional
interface card in the PC.
In addition, there are no
proprietary cables or
software.
• PC configuration: Because
a PXI cardcage is an exten-
sion of the PC backplane,
the whole system must be
rebooted every time a card
is inserted or removed. With
LXI, PCs do not require
rebooting when connecting
or disconnecting instruments.
What’s more, some modular
LXI instruments allow for
“hot-docking” of cards while
the power is on (Figure 1).
• Drivers: When a PXI system
reboots, the PC uses an
instrument discovery process
to identify newly connected
devices, which usually requires
operators to download and
install device drivers. The
LXI standard specifies the
use of IVI-COM drivers,
making it easier to work in
a variety of development
environments. And some
LXI instruments can be
programmed directly through
Standard Commands for
Programmable Instruments
(SCPI) when greater func-
tionality or performance
is required.
• User interface: With no front
panel interface, using
PC-based system software
to diagnose problems in
PXI and VXI devices can be
difficult. With benchtop LXI
instruments, the front panel
interface makes it easy for
developers to experiment
with an instrument. While
most modular LXI instruments
lack a front panel, their
built-in Web interface makes
it possible to learn the capa-
bilities by simply opening a
Web browser on the connected
PC. The browser function
also makes it easier to see
what’s happening with the
equipment, simplifying system
support and ensuring greater
uptime.
2. Performance
Automotive electronics test-
ing includes everything from
complex power train control
modules requiring hundreds
of tests, to simple airbag squib
modules, to telematic/infotain-
ment modules that may involve
time-consuming transfers of
huge data files. These tests
often challenge GPIB’s maxi-
mum data rate of roughly
1 MB/s. With LAN, I/O transfer
speed is becoming a non-issue
with 1-Gbit/s connections
becoming commonplace and
10-Gbit/s on the way.
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I/O performance should not
be an issue for LXI devices in
typical automotive applications
that require both transactional
programming and transfers of
large data blocks such as wave-
forms captured by digitizers.
In transactional programming,
there is a well-understood
issue around LAN latency.
Instrumentation vendors are
reducing the number of required
communication cycles by
preloading instructions to
LXI devices.
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