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Topic: PCF8574 interrupt questions (Read 1 time) previous topic - next topic


I can't find a really good explanation on specifically what the interrupt pin exists to do on the PCF8574/PCF8575 pin expanders. I'm assuming it alerts you when a state has changed on one of the pins? (but I also see comments on the timing/clock in many threads on the subject)

Is it possible to use such a port expander without using the interrupt at all? (if you poll it when you expect changes?) and is it even necessary at all for output pins?  I was curious to try to use one of them to expand the number of devices that could be controlled on short-pinned devices such as ATTiny chips or the ESP-01. But in some cases you end up with just the two pins (without micro-soldering onto the controller pin yourself) especially with the esp-01.

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