How to make use of Interrupts on pins 20 & 21 of a Mega when using an I2c LCD

Projects General Guidance
1

Hi everyone,

I want to make use of all 6 interrupts on an Arduino Mega. The project uses an I2C LCD which uses SCL and SDA which I have wired to and the LCD works fine. I have wired separate inputs to pins 20 & 21 which I want to trigger a falling edge interrupt function. I'm using attach interrupt to digital pin for all interrupts and the ones triggered from pins 2, 3, 18, 19 work fine, however when I enable the interrupts for pins 20 & 21 (SDA & SCL) they continue to fire and stop the LCD.
Is there a way of isolating the interrupts from SDA & SCL from pins 20 & 21 so I can make use of these interrupts with the LCD working in I2C mode? I can add some code however I'm sure the question should be sufficient for those in the know. Thanks

2

Those pins are physically the same. There is NO way to separate them. You might consider pin change interrupts if you need more interrupts.

3

You can use Pin Change INTerrupt PCINT on any pin.

4

DrDiettrich:
You can use Pin Change INTerrupt PCINT on any pin.

Not true for the used Mega.

5

This shows the PCINT pins.

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6

Thanks for the update. If not all so at least 24 pins are selectable for PCINT.

7

Always worthwhile asking - why would you wish to use interrupts? :roll_eyes:

8

Thank you