SC18IM704 interrupts

[jj100126]

Hello, I have a SC18IM704-EVB and I want to pair it with PCF8575, is there a way for the SC18 to accomodate the INT pin of the PCF? How does the host get the interrupt?

[JozefKozon]

Hello Joshua,

you can connect the !INT pin to one of the GPIOs pin in the SC18IM704. The GPIO pins are configured as inputs after reset. 

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You can make sure, that the used GPIO is set as input only by setting the PortConfx registers to 00 or 01.

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Then you by reading the IOState register of the GPIO pin, you can check if the !INT pin is asserted (LOW).

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With Best Regards,

Jozef

[jj100126]

i have thought of this as well, setting the GPIO as input, but how about on the host side? Should the host poll everytime for the input from the INT pin, and if there's one, the host then read the inputs from the PCF?

I am also thinking of ditching the INT pin and just let the host poll for the PCF inputs directly

[JozefKozon · Accepted solution]

Hello Joshua,

yes, that is correct. You need to poll for checking if the !INT was asserted low by reading the IOState register.

With Best Regards,

Jozef