jrz126

I have a 4x4 matrix keypad that I plan on using with a microcontroller someday. I'm also getting ready to put in an order to allelectronics and I was wondering if I should get one of these IC's
http://www.allelectronics.com/cgi-bi...144&type=store there is also a link to a datasheet there.

Would it be worth the 7.50?

EDIT: just found this IC here, http://www.allelectronics.com/cgi-bi...702&type=store for a 1 wire interface to a character LCD. (which my keypad also has)

Is there better IC's to use to keep my I/O pin count down for controlling the lcd and keypad?

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

Nigel Goodwin

You can interface both easily to a PIC, details for both in my tutorials!.

Far cheaper to use a 16F628 than pay $7.50 for a dedicated encoder IC.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

jrz126

well here's my predicament...
For my leds in the roof of my car, I'm planning on having all of the current driver circuitry in the trunk using shift registers and darylington arrays. I then want to add a microcontroller to this so that I can controll different display patterns, and be able to make adjustments with my keypad and LCD, which I need to mount up front.

This gives me a 15 ft span (after I route the wires under the trim and such) between the keypad/lcd and the microcontroller. I dont know how the microcontroller will handle this large length of wire, not to mention the elecronic noise it will be subjected to.

Another thought is since I'm going to be needing quite a few I/O pins to drive my leds, I could add another micro up front for the Keypad/LCD. So then I would have a 15 ft span between 2 micros.

Any suggestions?

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

Nigel Goodwin

One PIC at the front, connected to the keypad and LCD, with a second PIC at the back, controlling the LED's. Connect between them with a simple serial connection - no need for +/-12V RS232, just the 5V connection between two pins should be fine - probably not a bad idea to use screened cable though?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

MrMikey83

Heres something I found awhile back. Connect your keypad using only one I/O pin. You need a 555 timer and a handful of resistors. Good luck!
~Mike

__________________
All Electronic components run on smoke. Let the smoke out and it no longer works.
~Tim Baker (Electronics Instructor at John A. Logan College)

jrz126

is there a special type of shielding that I need?
like this one here: http://www.allelectronics.com/cgi-bi...S22&type=store

What is the drain all about?

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

Nigel Goodwin

No, I'd probably use normal twin screened cable, like you would for an audio lead.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

MrMikey83

I guess I forgot the link...

Heres the Schem.
http://www.elecdesign.com/Files/29/6303/Figure_01.gif
Connects a keypad through a 555 timer to a single I/O pin on the microcontroller.

~Mike

__________________
All Electronic components run on smoke. Let the smoke out and it no longer works.
~Tim Baker (Electronics Instructor at John A. Logan College)

bmcculla

I'd bet the keyboard encoder chip in jrz126's first post IS a PIC. Chips with those white stickers on them are usually microcontrollers (or EPROMs) with firmware burned in.

It might be worth adding a simple differential driver and using twisted pair. A bit of CAT5 would have enough nice twisted pair for a full duplex serial connection and some power and ground lines.