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When designing a microcontroller system, a
terminal or any other intelligent circuit that
needs to ‘show’ us something, an alphanu-
meric LCD is often the easiest way to obtain
a readout device. A good choice, really,
because LCDs are affordable, they offer a
clear readout and are relatively easy to drive
in software and hardware. Most commer-
cially available LCDs of the smaller variety
use the same controller IC, whether the dis-
play has 1, 2 or 4 lines of 8, 16, 20, 24, 32 or
40 characters. In all of these displays you will
typically find the Hitachi HD44780 controller
or a second source equivalent. The datasheet
of this ‘evergreen’ chip is available in the
form of a pdf (Acrobat Reader) document
from the
Hitachi website [1]. However,
because of the widespread use of these dis-
plays in electronic equipment, there are
many other sites on the web that deal with
this chip and way it is applied.
A fine page with plenty of information is
Ian Harris’ HD44780-Based LCD Modules [2].
On it Ian provides comprehensive informa-
tion on 2- and 4-line displays, including their
interfacing, display patterns and character
sets. You will also find many useful links
leading to application examples and other
sources of information. Another address for
information on this controller, connection
details of displays based on the HD44780, as
well as on LCD backlighting is that hosted
by Lampex [3], a manufacturer of all
kinds of LCDs.
If you need information on dis-
plays that do not fall in the ‘stan-
dard’ category, you should really
visit the LCD page at
EIO (Electron-
ics Information Online) [4]. This site
holds datasheets and specifications
of LCD products from most manufac-
turers in the field.
Driving a 44780-based LCD is not
difficult once you’ve absorbed some
of the relevant manuals that may be
picked up from the Internet. At
Peer’s LCD pages , published by
Peter Ouwehand, an extensive trea-
ELECTRONICS ONLINE
64 Elektor Electronics 11/2002
LCD Connections &
More
Technical details and applications
By Harry Baggen
Small alphanumeric LCD displays are applied in many electronic circuits,
particularly when microcontroller-driven. These displays are easy to
control and not expensive. However, you will always need to know their
connection details and other salient features. Fortunately the Internet
abounds with technical information on LCDs, as well as interesting
application briefs.