stupid question ...

bkiba

How would one go about setting up the basic stamp (BS2PE or BS2) to detect if a switch is thrown. I'm not talking about the 4 pin switches that come with the kits, I'm talking about a regular on off switch, with 2 pins.

I have a 4 key, illuminated key pad. two pins are for the LEDs, so + and - for those. Then there are 5 more pins, a common pin and a pin hooked to each individual key. When a key is pressed and held, the pin for that key and the common short. I'm trying to use the IN# command and debug the IN0, IN1, IN2, IN3 that I have the key pins hooked too, but it seems like whenever I press a key, the IN0-IN3 values randomly decide what they will be, with no repeatability.

Thanks

Beau Schwabe

bkiba,

"...When a key is pressed and held, the pin for that key and the common short. I'm trying to use the IN# command and debug the IN0, IN1, IN2, IN3 that I have the key pins hooked too, but it seems like whenever I press a key, the IN0-IN3 values randomly decide what they will be..."

If the "common pin" is GND, you need to use a pull-up resistor to Vdd with a value somewhere between 1K and 100K on each "pin for that key".

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

willy1067

Bkiba,

Keypads usually don't have each key attached to a pin, The first thing you should do is find the schematics for the key pad you are using, (googgled) or find the manufacturer web site.

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Fernando Gomez

revinc.us
gomez-rivera.com

Never compare yourself with anyone else, there will always be someone bigger·or·smaller·than you.

RDL2004

Do you get a random key in no matter which one you push or do you get the right key with a random value? It could be a bounce problem.

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- Rick

bkiba

Thanks for the suggestions.

The keypad is a storm backlit 4 button keypad.

It has a 7 pin connector

pin 1 - Cathode for LED
pin 2 - common
pin 3 - key D
pin 4 - key C
pin 5 - key B
pin 6 - key A
pin 7 - anode for LED

I've been pretty successful so far with electronics, I've never actually had a course or training on this stuff, so could you please explain what a pull up resistor is? Are you saying each pin 3-6 needs a resistor or just the ground/common pin?

thanks again!

phil kenny

Using Google for 'pull up resistor' brought this link up as the first one:

www.seattlerobotics.org/encoder/mar97/basics.html

Pull up resistor is the first topic discussed.

Good basic tutorial on electronics.

phil