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'16F84 code to interface HD44780?'
1998\03\28@005935 by Dan Larson

Can anyone point me to some 16F84 code for the
HD44780 display controller and also a code for
decoding a 4x4 row/col keyboard?

Also, for future reference, can some one point me
to any PIC List archives?

I got a hold of a nice POS credit card terminal with
a 4x4 keyboard, 16x1 LCD, Piezo beeper, 5V power supply...
I found it at a local surplus store.

I am going to carefully remove the proprietary uCU  chip
from it and wire in my own PIC.  I don't have any use for
the card swiper part, but I'll leave it intact for now.

The LCD controller is an HD44780A00. I have traced the E, RS, R/~W
and DB0-DB7 to the existing uCU.  Once it is removed, I will have
some nice solder pads to attach wires to for the PIC interface.

I haven't traced the keyboard yet but it appears to be a simple
4x4 row/col arrangement using those black rubber keys to close
the "comb" of traces at each intersection.

Adding a 16F84 and MAX232 would make it a nice terminal for a future PIC
project.  I will have to use a shift register to scan the colunm of the
keyboard and use another for the data lines of the HD44780 in order to
fit it all into 13 i/o pins! and still be able to use 2 i/o for RS232.

The finished device will make a very nice terminal for a future project!


* Dan Larson                  *
* Software Engineer           *
* Micro Control Company       *
* email: *

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