/*
   Project:       ATTiny85 Interrupt Test
   Description:   Shows relevant registers to set up
                  for various types of interrupts
   Creation date: 12/25/23
   Author:        AnonEngineering

   Inspired by
   https://docs.wokwi.com/parts/wokwi-attiny85   simulate ATTINY85 on wokwi
   https://wokwi.com/projects/317140124437578305  get interrupts working
   https://wokwi.com/projects/318885209198035539  debounce function.
   https://thewanderingengineer.com/2014/08/11/pin-change-interrupts-on-attiny85/ datasheet attiny85 ints.
   https://electronics.stackexchange.com/questions/264434/attiny85-interrupt-confusion "only PB2 on attiny85 can be used to trap edge changes"
   https://arduino.stackexchange.com/questions/66761/debouncing-a-button-with-interrupt

   Wokwi | questions
   AudioDiWhy — 12/23/2023 3:54 PM

   License: https://en.wikipedia.org/wiki/Beerware
*/

#include <TinyDebug.h>
// not needed in Wokwi
//#include <avr/io.h>
//#include <avr/interrupt.h>

#define INT0_VECTOR INT0_vect

const int BTN_PIN = PB2;
const int LED_PIN = PB0;
const unsigned long DEBOUNCE_TIME = 20;

volatile bool isInterrupt = false;
int value = 0;

ISR(INT0_VECTOR)  {
  isInterrupt = true;
}

bool debounceButton() {
  static int oldBtnState = HIGH;
  bool isButtonPressed = false;

  int btnState = digitalRead(BTN_PIN);
  if (btnState != oldBtnState) {
    oldBtnState = btnState;
    if (btnState == LOW) {
      isButtonPressed = true;
    }
    delay(DEBOUNCE_TIME);
  }
  return isButtonPressed;
}

void setup()  {
  Debug.begin();
  pinMode(BTN_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  cli();              // Disable interrupts during setup
  // set falling edge INT0 interrupt on PB2
  GIMSK = 0b01000000; // 9.3.2 GIMSK – General Interrupt Mask Register
  //GIFR  = 0b01000000; // 9.3.3 GIFR – General Interrupt Flag Register
  //PCMSK = 0b00000000; // 9.3.4 PCMSK – Pin Change Mask Register, any change
  MCUCR = 0b00000010; // Table 9-2. Interrupt 0 Sense Control, falling
  sei();              // enables interrupts
  Debug.println("Ready\n");
}

void loop() {

  if (isInterrupt)  {
    Debug.println("Interrupt!");
    isInterrupt = false;
    if (debounceButton()) {
      value++;
      Debug.print("Value: ");
      Debug.println(value);
      digitalWrite(LED_PIN, value % 2);
    }
  }
}