External Inturrupts

Projects Programming
1

dose anyone know why the following statement dosent compile

attachInterrupt(0, LiquidCrystal.keypadISR, LOW);

the keypadISR is in the library LiquidCrystal which i have modified

is there a way around this?

thanks in advance for any help

2

I think it is because at compile time the address of this function is not known, as there is no instance of LiquidCrystal at compiletime, it is created runtime...

3

so how can i call the routine?

4

so how can i call the routine?

You can't. You can not make an interrupt handler from a class method, unless that method is static. Otherwise, how would the interrupt vector know which instance the interrupt is for?

5

I would try something like the following - don't know if it works not tested - but at least the addresses can be resolved ...

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() 
{
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("hello, world!");
  
  Serial.begin(115200);
  Serial.println("Start...");
  
  attachInterrupt(0, myISR, LOW);
}

void loop() 
{
   Serial.println("...");  
}

void myISR()
{
  lcd.keypadISR();
}
6

ok thanks for that robtillaart your suggestion works

7

Great, learned something today :slight_smile:

8

Great, learned something today

But, of course, it isn't the sketch figuring out which instance of the LiquidCrystal class the interrupt is for. It was the programmer that did that.