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Topic: Reading Multiple Gates on One I/O Pin (Read 1 time) previous topic - next topic


I am trying to read when the state of one of 8 photogates goes low by checking one I/O pin, the timing requirement of the system does not allow me to poll 8 pins sequentially.  I would like to be able to set up an interrupt on one pin that would be trigger on a falling edge when any of the 8 gates goes low.

This may be a trivial question and an easy Google if I knew what the name of a device like was, but alas I do not.  Can someone give me digital hand?




I'm not entirely sure what you are trying to do, I'm guessing use a latching parallel to serial shift register.

You may not need to do that, it is possible to read 8 IO pins on the Arduino simultaneously (well nearly), as long as they are on the same port.

I write books about Arduino and Electronics: http://simonmonk.org


Nov 12, 2010, 09:41 pm Last Edit: Nov 12, 2010, 09:41 pm by AWOL Reason: 1
An 8-input NAND.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.


erm, yes - I see what you mean, I completely missed the point.

I write books about Arduino and Electronics: http://simonmonk.org



The NAND gate was exactly what I was looking for thanks.


Tim Williams

Why use a gate at all.

Use a 'wired or'.


Yes a diode wired to each device can be wired-ORed to create a single signal.


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