ATtiny85 and flow sensor (attachInterrupt on ATtiny85)

Hello everybody,

i would like to ask for your help with my code. I want to use hall effect flow sensor on attiny85. I already have run some code on arduino mega 2560, see code below. This code using command " attachInterrupt" and I am not sure how I should change this code to make it run on ATtiny85. I know that interupt pin on ATtiny85 is pin 7. Problem is that I need this pin for i2c communication protocol. Could you please advise me how should I change my code to make it run on ATtiny85?

Thank you for your help. Danosh

volatile int Filter_flow_pulse; //measuring the rising edges of the signal
int Filter_flow;                       
int Filter_flow_sensor = 2;    //The pin location of the sensor

void setup() {
     
   pinMode(Filter_flow_sensor , INPUT); //initializes digital pin as an input
   attachInterrupt(0, rpm, RISING); //and the interrupt is attached

   Serial.begin(9600);         //This is the setup function where the serial port is initialised,
}

void loop() 
{
Flow_update () ;     
}


void Flow_update ()     //This is the function that the interupt calls 
{ 
  Filter_flow_pulse = 0;      //Set NbTops to 0 ready for calculations
 sei();            //Enables interrupts
 delay (1000);      //Wait 1 second
 cli();            //Disable interrupts

 Filter_flow  = (Filter_flow_pulse * 60 / 7.5); //(Pulse frequency x 60) / 7.5Q, = flow rate in L/hour

// Serial.print (Filter_flow_pulse); //Prints the number calculated above

 Serial.print (Filter_flow  , DEC); //Prints the number calculated above
 Serial.print (" L/hour\r\n"); //Prints "L/hour" and returns a  new line 
} 

void rpm ()     //This is the function that the interupt calls 
{ 
  Filter_flow_pulse++;  //This function measures the rising and falling edge of the hall effect sensors signal
}

Could you please advise me how should I change my code to make it run on ATtiny85?

Your assumption that it is even possible is unwarranted.