I’m trying to use the PCF8574 as I don’t have enough inputs for the keyboard I’m trying to put together. I do not want to use scanning as this is a battery powered device but rather interrupt. How can I implement that. (The PCF8574 does not implement an interrupt interface… at least that I have found.)
Thank you
I don’t see any documented way of doing it with native component. MCP230xx might work for you better.
There are years I’m thick… I just need to wake the processor and let it do it’s normal operations. The interrupt I’ll wire to a pin to wake the ESP.
Thank you for your thoughts,
Ed
Not sure if I follow you now… Wire the pcf interrupt pin to esp wakeup pin with pullup.
But you don’t receive any key presses before esp starts scanning.
No, the ESP will not immediately receive the signal… It should see the pin low once it wakes up and (hopefully) recognize that the switch was pressed. (I hope to test and verify it works the way I hope it does in a couple of days.)
Assuming it works like I hope, I’m fine with it not seeing the press for several milliseconds. 
Ed