#include <Adafruit_TCA8418.h>

Adafruit_TCA8418 keypad;

volatile bool int_flag = false;

void ARDUINO_ISR_ATTR isr() {
  int_flag = true;
}

void setup()
{
  Wire.begin(D2, D3);
  Serial.begin(115200);
  while (!Serial) {
    delay(10);
  }

  if (! keypad.begin(TCA8418_DEFAULT_ADDR, &Wire)) {
    Serial.println("keypad not found, check wiring & pullups!");
    while (1);
  }

  keypad.matrix(8, 10);
  keypad.enableInterrupts();
  pinMode(D5, INPUT_PULLUP);
  attachInterrupt(D5, isr, FALLING);
  keypad.flush();
}

void loop()
{
  if (int_flag)
  {
    int k = keypad.getEvent();
    if (k & 0x80) Serial.print("PRESS\tR: ");
    else Serial.print("RELEASE\tR: ");
    k &= 0x7F;
    k--;
    Serial.print(k / 10);
    Serial.print("\tC: ");
    Serial.print(k % 10);
    Serial.println();
    keypad.flush();
    int_flag = false;
  }
}