Simple & Versatile Arduino Kitchen Timer with TM1637 Display

//-----------------------------------------------------
// Kitchen Timer with TM1637 Display
// by: mircemk
// License: GNU GPl 3.0
// Created: April 2025
//-----------------------------------------------------


#include <TM1637Display.h>

// Pin definitions
#define CLK 2
#define DIO 3
#define POT_PIN A0
#define START_BUTTON 4
#define RESET_BUTTON 5
#define BUZZER_PIN 6
#define RANGE_BUTTON 7

// Constants
#define QUANTIZE_INTERVAL 30    
#define POT_SMOOTHING 30        
#define POT_READ_DELAY 50       
#define ALARM_FREQ 500          
#define ALARM_ON_TIME 200       
#define ALARM_OFF_TIME 200      
#define COLON_ON_TIME 500      
#define COLON_OFF_TIME 500     
#define RANGE_DISPLAY_TIME 1000 
#define BUTTON_DEBOUNCE_TIME 300

// Timer ranges in seconds
const int TIMER_RANGES[] = {600, 1800, 3600};  // 10min, 30min, 60min
const int NUM_RANGES = 3;

// Display instance
TM1637Display display(CLK, DIO);

// Variables
unsigned long previousMillis = 0;
const long interval = 1000;     
bool timerRunning = false;
int remainingTime = 0;          
bool colonState = true;         
unsigned long lastBuzzTime = 0;
unsigned long lastColonToggle = 0;  
bool alarmOn = false;
bool displayOn = true;          
int lastDisplayedTime = -1;     
unsigned long lastPotRead = 0;
unsigned long lastDisplayFlash = 0;
int currentRangeIndex = 2;      // Start with 60min range (index 2)
unsigned long rangeDisplayStartTime = 0;
bool showingRange = false;      
unsigned long lastRangeButtonPress = 0;

// State enumeration
enum TimerState {
  IDLE,
  SHOWING_RANGE,
  RUNNING,
  ALARMING
};

TimerState currentState = IDLE;

void setup() {
  pinMode(START_BUTTON, INPUT_PULLUP);
  pinMode(RESET_BUTTON, INPUT_PULLUP);
  pinMode(RANGE_BUTTON, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);

  display.setBrightness(0x0a);
  updateDisplay(quantizeTime(readSmoothedPot()));
}

void loop() {
  unsigned long currentMillis = millis();
  
  switch(currentState) {
    case SHOWING_RANGE:
      // Stay in range display mode until time elapsed
      if (currentMillis - rangeDisplayStartTime >= RANGE_DISPLAY_TIME) {
        currentState = IDLE;
        lastDisplayedTime = -1;  // Force pot reading update
      } else {
        // Keep showing range
        displayRange(TIMER_RANGES[currentRangeIndex]);
        return;  // Skip all other processing while showing range
      }
      break;
      
    case IDLE:
      // Handle range button
      if (digitalRead(RANGE_BUTTON) == LOW) {
        if (currentMillis - lastRangeButtonPress >= BUTTON_DEBOUNCE_TIME) {
          currentRangeIndex = (currentRangeIndex + 1) % NUM_RANGES;
          rangeDisplayStartTime = currentMillis;
          lastRangeButtonPress = currentMillis;
          currentState = SHOWING_RANGE;
          displayRange(TIMER_RANGES[currentRangeIndex]);
          return;  // Exit loop immediately after changing to range display
        }
      }
      
      // Handle potentiometer input
      if (currentMillis - lastPotRead > POT_READ_DELAY) {
        lastPotRead = currentMillis;
        int potTime = quantizeTime(readSmoothedPot());
        if (potTime != lastDisplayedTime) {
          colonState = true;
          updateDisplay(potTime);
          lastDisplayedTime = potTime;
        }
      }
      
      // Handle start button
      if (digitalRead(START_BUTTON) == LOW) {
        delay(50);
        if (digitalRead(START_BUTTON) == LOW) {
          remainingTime = quantizeTime(readSmoothedPot());
          currentState = RUNNING;
          previousMillis = currentMillis;
          lastDisplayedTime = -1;
          colonState = true;
          lastColonToggle = currentMillis;
        }
      }
      break;
      
    case RUNNING:
      // Handle colon blinking
      if (colonState && (currentMillis - lastColonToggle >= COLON_ON_TIME)) {
        colonState = false;
        lastColonToggle = currentMillis;
        updateDisplay(remainingTime);
      }
      else if (!colonState && (currentMillis - lastColonToggle >= COLON_OFF_TIME)) {
        colonState = true;
        lastColonToggle = currentMillis;
        updateDisplay(remainingTime);
      }
      
      // Update timer
      if (currentMillis - previousMillis >= interval) {
        previousMillis = currentMillis;
        if (remainingTime > 0) {
          remainingTime--;
          updateDisplay(remainingTime);
        }
        if (remainingTime == 0) {
          currentState = ALARMING;
        }
      }
      
      // Check reset button
      if (digitalRead(RESET_BUTTON) == LOW) {
        delay(50);
        if (digitalRead(RESET_BUTTON) == LOW) {
          resetTimer();
        }
      }
      break;
      
    case ALARMING:
      handleAlarm();
      if (digitalRead(RESET_BUTTON) == LOW) {
        delay(50);
        if (digitalRead(RESET_BUTTON) == LOW) {
          resetTimer();
        }
      }
      break;
  }
}

void displayRange(int rangeInSeconds) {
  int minutes = rangeInSeconds / 60;
  uint8_t segments[4];
  
  segments[0] = display.encodeDigit(minutes / 10);
  segments[1] = display.encodeDigit(minutes % 10) | 0x80;  // Force colon on
  segments[2] = display.encodeDigit(0);
  segments[3] = display.encodeDigit(0);
  
  display.setSegments(segments);
}

int readSmoothedPot() {
  long total = 0;
  for (int i = 0; i < POT_SMOOTHING; i++) {
    total += analogRead(POT_PIN);
    delay(1);
  }
  int average = total / POT_SMOOTHING;
  return map(average, 0, 1023, 0, TIMER_RANGES[currentRangeIndex]);
}

int quantizeTime(int seconds) {
  int quantized = (seconds / QUANTIZE_INTERVAL) * QUANTIZE_INTERVAL;
  return constrain(quantized, 0, TIMER_RANGES[currentRangeIndex]);
}

void updateDisplay(int timeInSeconds) {
  if (currentState == ALARMING && !displayOn) {
    display.clear();
    return;
  }

  int minutes = timeInSeconds / 60;
  int seconds = timeInSeconds % 60;

  uint8_t segments[4];
  
  segments[0] = display.encodeDigit(minutes / 10);
  segments[1] = display.encodeDigit(minutes % 10);
  segments[2] = display.encodeDigit(seconds / 10);
  segments[3] = display.encodeDigit(seconds % 10);
  
  if (colonState) {
    segments[1] |= 0x80;
  }

  display.setSegments(segments);
  lastDisplayedTime = timeInSeconds;
}

void handleAlarm() {
  unsigned long currentMillis = millis();
  
  // Handle display flashing
  if (currentMillis - lastDisplayFlash >= 500) {
    lastDisplayFlash = currentMillis;
    displayOn = !displayOn;
    updateDisplay(0);
  }

  // Handle intermittent alarm sound
  if (currentMillis - lastBuzzTime >= (alarmOn ? ALARM_ON_TIME : ALARM_OFF_TIME)) {
    lastBuzzTime = currentMillis;
    alarmOn = !alarmOn;
    
    if (alarmOn) {
      tone(BUZZER_PIN, ALARM_FREQ);
    } else {
      noTone(BUZZER_PIN);
    }
  }
}

void resetTimer() {
  currentState = IDLE;
  timerRunning = false;
  noTone(BUZZER_PIN);
  alarmOn = false;
  displayOn = true;
  colonState = true;
  lastDisplayedTime = -1;
  updateDisplay(quantizeTime(readSmoothedPot()));
}