main.cpp

#include <Arduino.h>

String pin_label[] = { 
  "   15 (SDA): ", 
  "    4 (SCL): ", 
  "    9 (RST): " 
};

volatile unsigned int num_interrupts[] = { 0, 0, 0 };

void IRAM_ATTR sda_isr() { num_interrupts[0]++; }
void IRAM_ATTR scl_isr() { num_interrupts[1]++; }
void IRAM_ATTR rst_isr() { num_interrupts[2]++; }

void setup() {
  Serial.begin(9600);
}

void loop() {
  attachInterrupt(15, sda_isr, CHANGE);
  attachInterrupt(4,  scl_isr, CHANGE);
  attachInterrupt(9,  rst_isr, CHANGE);

  Serial.println("\nInterrupts:");
  for (size_t i = 0; i < 3; ++i) {
    Serial.println(pin_label[i] + String(num_interrupts[i]));
  }
  Serial.flush();
  
  delay(1000);
}