#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const int btnPlusPin = PA6;   
const int btnMinusPin = PA7;  
const int ledPin = PA5;    

LiquidCrystal_I2C lcd(0x27, 16, 2);

int counter = 1;     
const int maxCounter = 10;
const int minCounter = 0;  

bool lastPlusState = HIGH;
bool lastMinusState = HIGH;

unsigned long lastDebouncePlus = 0;
unsigned long lastDebounceMinus = 0;
const int debounceDelay = 200; 

unsigned long previousLedMillis = 0;
unsigned long previousLcdMillis = 0;
bool ledState = LOW;

void setup() {
  pinMode(btnPlusPin, INPUT_PULLUP);
  pinMode(btnMinusPin, INPUT_PULLUP);
  
  pinMode(ledPin, OUTPUT);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
}

void loop() {
  unsigned long currentMillis = millis();

  bool currentPlusState = digitalRead(btnPlusPin);
  bool currentMinusState = digitalRead(btnMinusPin);
  
  if (currentPlusState == LOW && lastPlusState == HIGH) {
    if (currentMillis - lastDebouncePlus > debounceDelay) {
      if (counter < maxCounter) counter++;
      lastDebouncePlus = currentMillis; 
    }
  } else if (currentPlusState == HIGH && lastPlusState == LOW) {
    lastDebouncePlus = currentMillis;
  }
  lastPlusState = currentPlusState;

  if (currentMinusState == LOW && lastMinusState == HIGH) {
    if (currentMillis - lastDebounceMinus > debounceDelay) {
      if (counter > minCounter) counter--;
      lastDebounceMinus = currentMillis; 
    }
  } else if (currentMinusState == HIGH && lastMinusState == LOW) {
    lastDebounceMinus = currentMillis;
  }
  lastMinusState = currentMinusState;

  if (counter > 0) {
    unsigned long interval = 500 / counter; 

    if (currentMillis - previousLedMillis >= interval) {
      previousLedMillis = currentMillis;
      ledState = !ledState; 
      digitalWrite(ledPin, ledState);
    }
  } else {
    digitalWrite(ledPin, LOW);
  }

  if (currentMillis - previousLcdMillis >= 200) {
    previousLcdMillis = currentMillis;

    lcd.setCursor(0, 0);
    lcd.print("Cnt:");
    lcd.print(counter);
    if(counter < 10) lcd.print(" "); 
    
    lcd.print(" Frq:");
    lcd.print(counter); 
    lcd.print("Hz ");

    lcd.setCursor(0, 1);
    lcd.print("Btn+:");
    lcd.print(currentPlusState == LOW ? 1 : 0); 
    lcd.print(" Btn-:");
    lcd.print(currentMinusState == LOW ? 1 : 0);
  }
}