Trouble shooting my Propeller board. Input/Output problems--grounding?

malcolm3000

I'm very new at this so please keep that in mind when responding.

Here is my problem.

I have my Propeller chip set up as shown in the kit schematic with two simple modifications. One, a simple push botton (10 ohm·resistor)·for the input and LED lights (100 ohm)·on two separate outputs. I have a simple program that takes an input and then this input creates two outputs--the LEDs.

When the input not on (open switch), there is an output on both the lights that happens once every few seconds and lasts for less. Also, just simply putting my hand on the push button in the off position causes the ouput signal to stay on!! Meaning the chip belives it has an input. I even went as far as removing the leads on the breadboard from the input then putting an open wire·into the breadboard for the input row and the output signals come on!!. The chip is seeing an input value with no voltage. However, when I also put in an open wire into the ground in the breadboard and leave my hand on this grounded wire, the output signal does not go high unless the pushbutton is closed.

I'm very perplexed but obviously·is this·some kind of grounding problem, or have a damaged chip?

Thanks,

Malcolm.

·

Beau Schwabe

Can you post a schematic and code?

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Joms

First off, I assume you mean 10,000 or 10K ohm resistor for the pullup/down.

Second, can you attached the code you are using so we can see if it is a something you missed in the programming?

malcolm3000

Please find code and schematic attached.

Thanks.

Malcolm.

malcolm3000

Here is the program in PDF format.

Malcolm.

Joms

OK, I think I see what is happening. The button input is 'floating' when the button is not pressed. An input to the prop *should* always be pulled either high or low and not left floating. That could cause all sorts of weird problems.

Try to use a 10K resistor, I messed up when I posted above. Although a 1k works, it just uses more power.

Anyways, connect one side of your button to ground. On the other side of the button connect the resistor from the button to 5v+, also connect a jumper wire from this side of the button to the input pin on your prop.

Hopefully you can follow that, if not, let me know back and I will draw something out for you...


EDIT - I attached a quick hand drawing of what·I was trying to explain...

Post Edited (Joms) : 4/20/2009 10:39:19 PM GMT

malcolm3000

Beau/Joms,

Thanks for replying.

Joms, I read your reply and followed your sketch. I·now understand that the inputs have to be 'pulled' if they are called in the program now it works as it should.

Thanks very much.

Malcolm.