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Index last updated: 2026-04-28 23:31 UTC

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Re: LPC2xxx GPIO Outputs Born LOW

2004-10-27 by markcrow

Yes, I actually tried setting the state (IOSET) before setting the 
direction to output with no effect.  And the 22xx user's manual does 
state that performing an IOSET on any bit which is an input will have 
no effect.  I also spoke with a Philips FAE after I sent this first 
message and he confirmed that output will definitely be born low and 
there's no workaround.

Thanks

--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
wrote:
> At 08:39 PM 10/26/04 +0000, you wrote:
> >I was surprised to discover that GPIO pins, just after they're
> >configured as outputs, default LOW (the opposite state of its 
startup
> >high-impedance input mode).  For my design, LOW is an ACTIVE state.
> >I can immediately set the output HIGH but I'm stuck with a
> >LOW 'glitch' to deal with.  Every other micro GPIO I've worked with
> >would maintain the HIGH when switching from input to output mode.
> 
> Just a stab in the dark, I would have thought they would default to 
the 
> state of the output register.  Did you set the output before 
changing to 
> output?
> 
> 
> 
> Robert
> 
> " 'Freedom' has no meaning of itself.  There are always 
restrictions,
> be they legal, genetic, or physical.  If you don't believe me, try 
to
> chew a radio signal. "
> 
>                          Kelvin Throop, III

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