Could i add time bonus feature to stopwatch project ???

Projects Programming
1

Hey guys !
Currently working on a arduino project that needs a stopwatch. I have the stopwatch done and it will use two buttons: one to start or reset the count and another to stop counting and show the elapsed time.

My question is how would i go about adding a time bonus feature that will +2 seconds to elapsed time when a button is pushed. So ill have three buttons in total
one to start or reset the count
one to add seconds to the elapsed time whenever it is pressed
and another to stop counting

here is my current code
.

unsigned long start, finished, elapsed;
void setup()
{
 Serial.begin(9600);
u pinMode(2, INPUT); // the start button
 pinMode(3, INPUT); // the stop button
 Serial.println("Press 1 for Start/reset, 2 for elapsed time");
}
void displayResult()
{
 float h, m, s, ms;
 unsigned long over;
 elapsed = finished - start;
 h = int(elapsed / 3600000);
 over = elapsed % 3600000;
 m = int(over / 60000);
 over = over % 60000;
 s = int(over / 1000);
 ms = over % 1000;
 Serial.print("Raw elapsed time: ");
 Serial.println(elapsed);
 Serial.print("Elapsed time: ");
 Serial.print(h, 0);
 Serial.print("h ");
 Serial.print(m, 0);
 Serial.print("m ");
 Serial.print(s, 0);
 Serial.print("s ");
 Serial.print(ms, 0);
 Serial.println("ms");
 Serial.println();
}
void loop()
{
 if (digitalRead(2) == HIGH)
 {
 start = millis();
 delay(200); // for debounce
 Serial.println("Started...");
 }

 if (digitalRead(3) == HIGH)
 {
 finished = millis();
 delay(200); // for debounce
 displayResult();
 }
}

any reading material that will be beneficial will be appreciated
Thanks !

2

The simplest way would be to subtract 2000 (ms) from the start time, so that the elapsed time would appear 2 seconds longer. The coding will vary depending on whether you want to press the button while the timer is running, or after the stop button is pressed. Something like this...

if (digitalRead(thirdButton) == HIGH)
{
  start -= 2000;
  delay(200); // for debounce
  Serial.println("Bonus added");
}

For further reading you should look at debouncing using millis().