Kat
I am confused...

Yes while the Line is set to OUTPUT and the SW is pushed, it will short the
LINE OUT..  BAD IDEA... HA....

Well add a Resistor in series with the SW,  (Got to consider the SINK Current)

Then it is safe to PUSH the SW, but this will TURN off the LED if it is ON...

Still NOT GOOD...

Well if you can't do it, just scrap this idea...

Good luck,
Dan
(PS But I seen drawing where it is being done....!!!!!!!  Can you believe that)
But this was in a Multiplexed Key Pad Scan type circuit..  The switches are
in series with the Scan and are shut off once the LED is being.  They don't
go directly to GND of 5V...  They conect to other LINES of the MCU
and are toggled in and out.  There is never a conflict with the LED Circuit

========================================



Kathy Quinlan wrote:

> I am the only person to spot this floor or is the morphine screwing my mind
> ?
>
> If the output is high to drive the led and you push the push button, you get
> an instant Pic Pin to ground short ?
> Even If I am wrong, it will atleast turn the led off :o) and IIRC the OP
> wanted the switch to neither turn the led on or off with the switch.
>
> Regards,
>
> Kat.
>
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> ____________________________________________________________________________
>
> ----- Original Message -----
> From: "Dan & Vijay Marchesani" <danvj@EARTHLINK.NET>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Saturday, September 29, 2001 7:44 PM
> Subject: Re: [EE]: Multiplex LED and switch on I/O pin
>
> > Dan & Vijay Marchesani wrote:
> >
> > > Hi Dave
> > >
> >
> > (Reposted DRAWING due to error in TEXT format)
> >
> >
> > Then follow your wiring of the LED, R1 - Resistor (100 to 600 Ohms),
> > add (two) 1N914 Diodes, and Switch below.....
> >
> > |-------/\/\/\/\/\/\/\----5V (Internal to Pic, WEAK PULL UP)
> > |
> > |                       (LED With (2) 1N914 Diodes)
> > *----I/OPin---*---|>|--|>|--|>|--/\/\/\/---GND
> >                        |
> >                        |
> >                        |               \
> >                        |--------*   \--------------GND
> >                                  Switch
> >
> > Dave
> > The Switch has to SHUNT the LED, this is only way to keep the
> > LED from turning on...
> > Dan
> >
> > --
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> >
> >
>
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