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Topic: old question interrupt expansion (Read 602 times) previous topic - next topic


How best to expand Arduino external interrupts?

This must be a question of FAQ type, but I can't find many available solutions online for it. I read that one way is to use 2 Arduinos: one that has the interrupt enabled on the pin change, and the other that reads and acts when interrupted by the first one. The other way seems to be done by GIOP expander chips, which I still can't figure out how (if at all possible).

May be there are ready interrupt controllers we can use?

Please point me to the direction. Thanks.


Two Arduinos is way overkill.

Pin change interrupts.
AND/OR gate.
IO expander.
Diode ORing.
Priority encoder.

How about you tell us what you need to do.

Rob Gray aka the GRAYnomad www.robgray.com



The pinchangeint library gets you around 20 interrupts on a standard arduino uno. Its easy to use, efficient and well supported. I use it a lot and have a overview posted on my blog here -


obviuosly its not the complete solution if you need more than 20 interrupts, but for 20 or less i dont think there is any need for you to look anywhere else.

Duane B


Read this
then watch this


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