Countdown Timer Help Please

Using Arduino Project Guidance
1

Many hours of searching and trial/error but I need help now. I'm trying to build a countdown timer that only counts down while a button is being held down. When the button is not held down, I would like the countdown to pause. When the button is held down again, I would like the countdown to resume. I feel like this is so simple that I'm over-thinking it. My code is below, but please don't get side-tracked by how bad it is...I'm a newb. If its easier to start over fresh, I'm perfectly fine with that. Thank you

#include <EEPROM.h>
#include <LiquidCrystal.h>
int X;
int Y;
int Z;
int W;
int V;
int U;
int T;
int x = -1;

int address = 0;
int airAddress = 1; 
const int airTime = EEPROM.read(airAddress) - EEPROM.read(address);

int button1 = 8;
int button2 = 9;
int button3 = 10;
int previouslyPressed1 = 0;
int previouslyPressed2 = 0;
int buzzer = 13;
int AA = 0;
int stopSecond = 0;     //stopwatch seconds
int stopMinuite = 0;    //stopwatch minutes 
int theTime;
int Latch;

LiquidCrystal lcd(12,11,5,4,3,2);

void setup(){
  
  pinMode(button1, INPUT);
  pinMode(button2, INPUT);
  pinMode(button3, INPUT);
  pinMode(buzzer, OUTPUT);
  lcd.clear();  
lcd.begin(16,2);  

W = 300;
U = 0;    //These are the "seconds" in Timer
T = airTime;    //These are the minutes in Timer
lcd.print("   GIA Timer");
delay(500);
  lcd.clear();
}
  
  
void loop()
{
 while (x == -1){      //This is the start screen  x==-1 is normal
 lcd.setCursor(0,0);
 lcd.print("Timer - 1");
 //lcd.setCursor(0,1);
 //lcd.print("Stopwatch - 2");
 
 /////////////////////////////START SCREEN END//////////////////////////////////////////
 
 
 /////////////////////////////OPTIONS MENU/////////////////////////////////////////////
 if(digitalRead(button3) == HIGH)    //this enters timer mode
  {x = 0;
  lcd.clear();}
    
    /*if(digitalRead(button2) == HIGH)  //this enters stopwatch mode
  {
     x = 5;
    lcd.clear();
    lcd.print("Stopwatch");
    delay(1000);
    lcd.clear();
  }*/
}

/////////////////////////////THIS IS ENTERING THE TIMER MENU//////////////////////////
while (x == 0)    //this screen is for setting the minutes for the timer (also button 3)
{
  while(AA == 0){
   lcd.print("Minute Hand");
  delay(1000);
   AA = 1;
   lcd.clear();
  }
  
  if ( T < 0 )
  {
    T = 0;
lcd.clear();  
}
  /*if((digitalRead(button1) == HIGH)   &&  (previouslyPressed1 == 0)) {  //timer minute increase by 1
    T = T + 1;
    previouslyPressed1 = 1;
    delay(50);
    lcd.clear();
  }
      if((digitalRead(button1) == LOW)   &&  (previouslyPressed1 == 1)) {  //unknown
    previouslyPressed1 = 0;
    delay(50);
}
  if((digitalRead(button2) == HIGH)   &&  (previouslyPressed2 == 0)) {  //timer minute decrease by 1
    T = T - 1;
    previouslyPressed2 = 1;
    delay(50);
    lcd.clear();
  }
        if((digitalRead(button2) == LOW)   &&  (previouslyPressed2 == 1)) {  //unknown
    previouslyPressed2 = 0;
    delay(50);
}*/
lcd.setCursor(0,0);
lcd.print(T);
lcd.print(":");

if (U > 9)
{              //The U portion is for, example: "12" and "4" (i.e. to eliminate zeros
lcd.print(U);
 }
else{
 lcd.print("0");
 lcd.print(U);
}
///////////////////////////////////////MINUTES SCREEN END////////////////////////////////  
  
/////////////////////////////////////SECONDS SCREEN BEGIN///////////////////////////////
  if (digitalRead(button3) == HIGH)    //this is if you press button 3 after your finished
  {                                     //selected the minutes (enters the "seconds" screen)                             
   x = 1;
   V = (millis()/(1000));
   lcd.clear();
   lcd.setCursor(0,0);
   lcd.clear();
   lcd.print("Second Hand"); 
   lcd.setCursor(0,1);
   lcd.print("(Hold to ignore)");
   lcd.setCursor(0,0);
   delay(1000);
   lcd.clear();
  }}

 while (x == 1)    //this screen is for setting the "seconds" for the timer
  {
    if ( U > 59 ){    //this ensures that the seconds work properly
    U = 0;}
    if(U < 0){
      U = 59;
    lcd.clear();}
  /*if((digitalRead(button1) == HIGH)   &&  (previouslyPressed1 == 0)) {  //timer second increase by 1
    U = U + 1;
    previouslyPressed1 = 1;
    delay(50);
    lcd.clear();
  }
      if((digitalRead(button1) == LOW)   &&  (previouslyPressed1 == 1)) {  //unknown
    previouslyPressed1 = 0;
    delay(50);
}
  if((digitalRead(button2) == HIGH)   &&  (previouslyPressed2 == 0)) {  //timer second decrease by 1
    U = U - 1;
    previouslyPressed2 = 1;
    delay(50);
    lcd.clear();
  }
        if((digitalRead(button2) == LOW)   &&  (previouslyPressed2 == 1)) {  //unkown
    previouslyPressed2 = 0;
    delay(50);
}*/
  lcd.setCursor(0,0);
  lcd.print(T);
  lcd.print(":");
  
  if (U > 9){    //Ensures proper zeros
  lcd.print(U);
 }
else{
 lcd.print("0");
 lcd.print(U);

}
  
  ////////////////////////THIS IS WHAT HAPPENS AFTER HITTING THE "TIMER START" BUTTON////////
  if (digitalRead(button3) == HIGH && digitalRead(button2)==HIGH)
  {
   x = 2;                  //while timer is started, set x = 2
   if (T > 0){      //if timer minutes greater than zero
 W = (T*60) + U;}   //this is the total number of seconds
else{
  W = U;}
  lcd.clear();
  lcd.setCursor(0,0);
  V = (millis()/1000);
}
  
}


////////////////////////////THE TIMER STARTS HERE////////////////////////////////////

X = (W - (millis()/(1000))) + V;
  
  //Here is the Second to Minute-second Conversion. X is the second input
Y = X/60; //Y is the minute output
Z = X - (60*Y); //Z is the second output

  // This is the display of the minutes
lcd.setCursor(0,0);

lcd.print(Y);
lcd.print(":");

if (Z > 9)
{
lcd.print(Z);
lcd.print("   ");
}
else
{
  lcd.print("0");
  lcd.print(Z);
  lcd.print("  ");
  
}
if((Y == 0) && (Z == 0))
{ 
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Timer is over");
 while(digitalRead(button3) == LOW)
 {
  digitalWrite(buzzer, HIGH);   // turn the buzzer on (HIGH is the voltage level)
  delay(100);               // wait for a second
  digitalWrite(buzzer, LOW);    // turn the buzzer off by making the voltage LOW
  delay(100);
  }
 x = -1;
 delay(1000);
 lcd.clear();
 AA = 0;
}
////////////////////////THE END OF TIMER AND ALL ASSOCIATED FUNCTIONS//////////////////////


////////////////////////START OF THE STOPWATCH AND FUNCTIONS//////////////////////////////
/*while(x == 5){

if(stopSecond > 59)
{
  stopSecond = 0;
  stopMinuite = stopMinuite + 1;
   theTime = theTime + 60;
}
  
lcd.setCursor(0,0);
lcd.print(stopMinuite);
lcd.print(":");
if (stopSecond > 9){
lcd.print(stopSecond);}
else{
  lcd.print("0");
  lcd.print(stopSecond);}

if((digitalRead(button3) == HIGH) && (Latch == 0))
{
   Latch = 1 ;
  theTime = (millis()/(1000));
    digitalWrite(buzzer, HIGH);   // turn the buzzer on (HIGH is the voltage level)
  delay(100);               // wait for a second
  digitalWrite(buzzer, LOW);    // turn the buzzer off by making the voltage LOW
  delay(100);
}
if( Latch == 1)
{
   stopSecond = (millis()/(1000)) - theTime ;  
}
//if(digitalRead(button2 == HIGH)){
//Latch = 0;}

if(digitalRead(button2) == HIGH)
{  
  Latch = 0; 
  digitalWrite(buzzer, HIGH);   // turn the buzzer on (HIGH is the voltage level)
  delay(100);               // wait for a second
  digitalWrite(buzzer, LOW);    // turn the buzzer off by making the voltage LOW
  delay(100);
 // stopSecond = 0;
 // stopMinuite = 0;
}
if(digitalRead(button1) == HIGH)  //if x=-1 then go back to main menu
{  
x = -1;
}*/
}
2

What your are asking is simple, but your code have to much "garbage". Do you figure out alone what you need to do with a simple sketch that only do what you are telling?

3

I'm sorry, I don't fully understand what you are asking me.

4

Have you taken a look at the Blink without Delay example sketch?

You can play around with this.

const byte buttonPin = 2;
int timer = 15;
uint16_t prevTime = millis();

void setup()
{
  Serial.begin(115200);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() 
{
  byte button = digitalRead(buttonPin);
  if((millis() - prevTime >= 1000) && (button == LOW) && (timer >= 0))
  {
    prevTime = millis();
    Serial.println(timer);
    timer--;
  }
  if((timer <= 0) && button == HIGH)
    timer = 15;
}
5

There you have the code. Now let's see if you understand now my question.

Good work.

6

Ok, now I see a basic countdown without all the garbage. How would I make this countdown start while holding a button down and then stop when I am not holding down that button, yet resume when I go back to holding down that same button?
Thanks guys!

7

Did you try the code I posted?

8

Yes, I tried the code but I couldn't pause the countdown once it started...it just kept going until zero and then started again at 15 until zero. I must be missing something here.

9

The button is wired to be brought low when pressed, not high.

10

How is your switch wired.

11

Ah, gotcha! My switch was the problem here. It's working properly now. I'll try and integrate this into my code and see if I can get it to work. Thanks!

12

I have been using the code below for the simple countdown timer but now I've noticed something very odd. At exactly every 65 seconds of counting down, the serial monitor starts jumping to seemingly random numbers. I've tried two different Arduino Uno's with the same result. Any ideas what could be causing this?

int timer = 100;
uint16_t prevTime = millis();

void setup()
{
  Serial.begin(115200);
}


void loop() 
{
  if((millis() - prevTime >= 1000) && (timer >= 0))
  {
    prevTime = millis();
    Serial.println(timer);
    timer--;
  }
  if(timer <= 0)
    timer = 15;
}
13

You're trying to store millis in an unsigned int, hence the issue after 65535 milliseconds. replace this:

uint16_t prevTime = millis();

with this:

unsigned long prevTime = millis();