Hello,

I am wondering if it is possible to multiplex a pushbutton switch
input and an LED output on the same I/O pin.  My idea is that since
the switch input only needs to be sampled every 2ms, it can be set as
an output for an LED when not sampling the switch.  Also, when the pin
is switched to input to sample the switch, the time taken to do so is
so minimal, that the LED would not even flicker.  I figure the I/O pin
only needs to be set as an input for just a few assembly instructions.
Hardly noticeable, right?

So, I've got a couple questions.  First off, is the idea described
above even possible?  And finally, what would the resulting circuit
look like?  I've come up with this:

              LED   R1
           +--|<|--/\/\----o +5V
-----+     |
 I/O |     |
 Pin +-----+
     |     |          \
-----+     |           \
           +--/\/\--+   +--o Gnd
               R2    SW1

However, I cannot seem to come up with R1 and R2 values that work when
the switch is closed, and the pin is setup as an input.

Thanks for any help!

-Dave

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