Floating input

Jsav

Howdy all,
··· My problem is that I'm using a pushbutton as a condition with which to initiate a bunch of actions, and I'm having trouble controlling what the basic stamp sees.

The circuit I'm using (x3) is given by page 90 of the What's a Microcontroller - Student Guide, or http://www.parallax.com/Portals/0/Downloads/docs/books/edu/Wamv2_2.pdf

When the pushbutton is depressed, IN3 reads 1 as long is it's depressed and the LED will blink on and off as suggested, however, when the pushbutton is not depressed IN3 has a tendancy to float between 1 and 0, and I'm not sure why. I can't program for actions that are based on the condition of IN3 (0 or 1) if it keeps floating between, obviously I want it to be 0 when left alone and be 1 when and only when the pushbutton is depressed.

Any suggestions on why IN3 is floating? or what I can do to remedy this.

It also happens on any input pin, not just 3.

Beau Schwabe

Jsav,

Are you using a 10K pull-down resistor as suggested on page 90?

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Jsav

Yup, well it's more like 9.8k due to manufacturing error, they're all a little off, like 9.8k, 460ish and 218ish, all slightly lower, but is that enough to cause this problem?

Jsav

Here's an idea of my code with two LED's and 1 pushbutton

' {$STAMP BS2p}
' {$PBASIC 2.5}

DO
DEBUG ? IN5
PAUSE 800
DEBUG ? IN7
PAUSE 800

IF (IN5 = 1) THEN
HIGH 13
PAUSE 50
LOW 13
PAUSE 50
ELSE
PAUSE 100
ENDIF

IF (IN7 = 1) THEN
HIGH 15
PAUSE 50
LOW 15
PAUSE 50
ELSE
PAUSE 100
ENDIF

LOOP




in this case, both LED's blink accordingly when the pushbutton is depressed, connected to pins 13 and 15 respectively, but again, the debug displays that pin5 and pin7 are floating between 1 and 0 when the pushbutton is left alone.

vaclav_sal

I run you code and see the unnused pins (not pulled up) always at 0.

I am using 100KOhm pullup and see always·1.

Please explain what do you mean by "floating " between 0 and 1.

Do you mean alternating between 0 an 1 ?·

Jsav

Yes I do mean alternating between 0 and 1 (on the debug screen based on the IN5·? prompt), I'll try it with different resistors, the 220's there to protect the input pins of the stamp, do u have a resistor there?

Jsav

Also, pull up or pull down, either situation results in a pin that alternates between 1 and 0 reguardless if the pushbutton is depressed

Jsav

I have resolved this problem, thank you both for the prompt replies. [noparse]:)[/noparse]