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[ts-7000] Re: Random state at DIO_14 of TS-7400

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Subject: [ts-7000] Re: Random state at DIO_14 of TS-7400
From: "gebbet00" <>
Date: Tue, 20 May 2008 03:33:23 -0000
> DIO_14 should be powering up as an input.  
That's what I thought, but I couldn't find where did I read it.

>If you try to read the value it 
> is going to look random, but since it is an input you aren't going
to be 
> able to drive anything or sink any current.
I'm not reading it. Pin is connected to a NPN transistor via a voltage
divider of two 4.7K resistors, one from pin to transistor's base and
one from there to ground ( common emmiter ).

My thought is such load souldn't be mantained at 3.3V at pin side but
it is. That's why I ask if pull-up resistor has anything to do with it.

Transistor ( 2N2222 ) is fully saturated. Could it be that input
characteristics are enough to drive that and I should make it a
heavier load? 10K doesn't seem a specially light load.

I haven't tried to make sure it's an input and test behavior, but when
I do make sure it's an output with low state, voltage goes to zero, so
it's obviously correctly tested.

In case my deduction is correct and it's awaking as random output (
either by itself or as kernel' side effect ), how could it be
corrected? It seems to go high as soon as kernel starts boot ( haven't
tested more accurately than simple observation ) so a small program
that makes it go low is no good, since there's at least one second
between boot and such control

Ideas?

Gabriel Rojas C



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