Hardware Reference
In-Depth Information
Chapter 4
Driving a Simple Character LCD
Character LCDs seem less of a craze and more of an old technology these days, although I've still got a soft spot for
them (much like I do for valves and tubes). I can recall when everyone that was modding PCs wanted a small 18-by-2
character LCD modded into their case. I remember the details quite well: more often than not I was the one doing
the wiring jobs for them. There were many nights spent cutting up parallel port cables and wiring them into the little
LCDs. Then everyone watched in joy as I would write some simple characters to prove that the LCDs did in fact work.
After all there was something “high-tech” about being able to display your CPU temperature or your current playing
song or even something as simple as the time on a little LCD screen. You can see in Figure
4-1
a simple character LCD
displaying the time. These LCDs are everywhere these days. You will find them in printers, vending machines and
payphones, or, in my case, by the cabinetful in local electronics markets, of every shape and size. You may even be
able to recycle one from a dead device you have lying around. It should be quite simple to desolder the LCD out of the
broken device.
Figure 4-1.
A simple character LCD clock
Given that an 18-by-2 LCD would also fit neatly into a 5.25-inch bay on your standard PC case, this may have
been why such screens became so popular. Back then it was the Hitachi HD44780 and its clones that everyone was
using. The stock size was 18 by 2 but screens do get much bigger. I did manage to get my hands on a 20-by-4 HD44780
clone and everyone I knew was most envious. I had four full lines of 20 characters that displayed the track listing,
systems info, and, of course, the date and time. Given what your average mobile phone these days can achieve
resolution-wise, 20 by 4 now seems a lot less impressive.
