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RE: using character LCD as display.

From: Doug Sutherland <>
Date: Thu, 20 Mar 2003 08:36:52 +0100

Jeremy wrote:

 > This one allows for Full-sized AT keyboard. Would that work?
 > http://www.matrixorbital.com/products/lk404-at.htm

This is interesting ... it's a new product from matrix orbital.
They don't mention the keyboard interface in the manual! This
has potential but I wonder how it will behave as a "terminal"
because there are issues about how lines are displayed and
how backspace and all of that works. The other thing about
these LCDs are that the controllers are not exactly small,
they are two stacked PCB boards, so the overall bulk of the
display is a bit cumbersome. Not the DB9 connector on the
back, that would need to be removed I think otherwise you
have a big connector on the back.

I "flattened" one of the small LCDs from scott edwards by
separating the two PCBs and connecting them with some ribbon
cable. This way the display is very thin and the second PCB
sits beside the other rather than stacked. This is the one
that I hacked on:

http://www.seetron.com/sgxmnl.htm

Back to this matrix orbital LK404-AT ... in my opinion it
would be better to use a microcontroller and write some code
for interfacing both an LCD and PS/2 keyboard. This way you
can tweak the behavior of the terminal. I am suspecting that
the LK404-AT won't exactly work properly as a terminal when
connected to a getty process (linux serial terminal).

The other thing to consider is this: a normal console on a
VGA monitor is 25 lines of 80 characters or 2000 characters
per screen. The LK404-AT is 4x40 or 160 characters per
screen. This is only two lines of console output, and the
40 character width is too small for many things, I know
because I tried it. For a usable terminal as console you
need more than 40 character width and more than 4 lines in
my opinion. I saw one noritake display that had something
like 16 lines of 50 characters ... this would give much
better real estate ... that's 800 characters per screen
or 40% of the real estate of a normal 80x25 terminal.

Here's an application note for interfacing a PS/2 keyboard
with a protean logic microcontroller

http://www.protean-logic.com/applications/an039.pdf

I have seen keyboard code for Atmel AVR microcontrollers
in several places too.

   -- Doug

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