Interruptions - Method getLastInterruptPin() always returns 0 even if port 0 is not set for interruptions or set up as input

[izamoramx]

You might want to review the getLastInterruptPin() method. I tried a simple test using port B as input and port A as output modifying your interruptions sample code. Pin 0 (Port A) is set as output and I have an LED connected to it for debugging, and pin 8 (Port B) is set up as input with a button wired to it.

The interruptions correctly trigger when the state of pin 8 changes, however when polling the register for the interruption ports and values, it will always return pin 0 as the one that trigger the interruption. I don't see anything on the method that validates if the pin is set as an interruption pin or event as an input, but I don see the first thing the code checks if for the value of PortA but by bit, which explains why the method always stops at pin 0. I am not sure why the register if the MCP23017 is setting pin 0 as an interruption either since there are at least two places in the sample code that clear the INT register. If I comment out the block that checks for port A, the method correctly returns port 8 as the port that triggered the interruption.

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[PsuFan]

I have seen this issue too. Root cause was a floating not connected input with a interrupt enabled from previous compile not being reset. This floating interrupt floods the chip/data line with messages making it impossible to even control outputs. Ensure all interrupted pins are high and add code to begin from PR #55 to disable previously interrupted pins or ensure chip is reset.

[izamoramx]

@PsuFan thanks for the reply. I am not sure which code you are referring to. Maybe I missed it, if so please let me know. Otherwise it seems that the solution you are referring to has been implemented to the latest version of the library. If I understand this correctly, I will update my version to use this latest fix. Thanks again.

[PsuFan]

Yes that is correct, see how the latest version works. A change to the interrupt example was also approved that ensures the interrupt is cleared.

Again ensure all interrupted pins are high (or low) as desired and not floating.

[izamoramx]

Ok fantastic!

You mean only the pins actually being used as INT correct? Not all the possible INT pins on the chip. I do have some pins that are part of the INT group but they are being used for other purposes. I would expect those wouldn't be affected.

[PsuFan]

Yes the pins you define with mcp.setupInterruptPin(THIS_PIN,FALLING);

[izamoramx]

Ok great. Thanks again! I will try that

[caternuson]

@izamoramx Did the suggestions above resolve this?

[izamoramx]

@izamoramx Did the suggestions above resolve this?

@caternuson Sorry, I haven't had a chance to test the latest version of the library for this issue as I have to pause on that project to work on others but I am expecting to resume that in the next month or so and will be able to verify if the issue persists or not and get back to you.

[caternuson]

OK, please also update to the 2.0.0 release of the library:
https://github.com/adafruit/Adafruit-MCP23017-Arduino-Library/releases/tag/2.0.0
It changes things a lot.

[caternuson]

Closing. Hoping fixed. Can reopen if still an issue.