I can't beleive this works! :D

Hi Guys,
If you connect an LCD as described in the manual, there are exactly seven port pins left on a 16F84/628. A 3x4 matrix
keypad generaly requires seven pins, but I was able to flog the
LCD data port for the keypad scan outputs since no program
will ever scan the keypad and write to the LCD at exactly the same time.. and now there's four spare pins for speakers, switches, etc.

At the moment, the only hardware bug is holding down three or
more keys will cause jargon on the display, so I will stay away from keypad combinations for activating menu functions.

Now I'm thinking it would be better to use the 4 bit LCD data port
as inputs for the keypad scan routine, and switch back to output
for the PBP LCD libraries.
Cheers, Art.

Art,

If you need a couple more pins, you could use the internal oscillator of the 16F628.

Then if you move the LCD Enable line from RB3 to RA6, you can use the CCP module (HPWM) to control the brightness of the LCD backlight.

Just an thought.

Very Cool!!!
Nice project!!!
Great drawing also!!
I've been able to save pins on a keypad by using an A/D input and configure the keypad wires to 11 resistors in a series voltage divider ladder.
No button pressed is a specific voltage output from the resistive divider circuit.
Every pad button pressed produces its own voltage.
FUN STUFF!!! :-]

Hi Art,
I feel that way every time I make something that works :D

And it still works ten years later!! :D

http://defxev.webs.com/Pilot_Prototype2.jpg

Should have made a special character for #.

Robert
:)

Lol, that would use more memory defining the character,
and sending it to LCD CGRAM.
So long as I had the memory, you are right :)

I think I could have also flogged pin RA4 to use any time other than when LCDOUT is printing.

Most importantly, I should not have done this:
http://farm3.static.flickr.com/2438/...6d6a68db_o.jpg
Which is why I'm suprised it STILL works! Too bad if I ever dropped it.

Now I have to hope this thread get buried again! :D

Quote:

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Originally Posted by Art

Now I have to hope this thread get buried again! :D

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BUMP :D
bump :D