Creating a Timer/stopwatch with an LCD

Forum 2005-2010 (read only) Software Syntax & Programs
1

I'm having trouble writing code to create a stopwatch/timer. I'm using an Arduino Mega board and a 20x4 LCD screen. This timer is only one portion of the data I'll be displaying. Below is the code I've written do calculate the time:

int getE_minutes() {
  double Emin;
  int curTime = millis();
  Emin = floor((curTime - pumpStartTime)/60000);
  Serial.print("Minutes: ");
  Serial.println(Emin);
  return Emin;
} 

int getE_seconds(int Emin) {
  int curTime = millis();
  double sec = (curTime - pumpStartTime)/1000;
  int Esec = floor(sec - (60*Emin));
  Serial.print("Seconds: ");
  Serial.println(Esec);
  return Esec;
}

I've written them as functions so that I can call it whenever I need to and not have them taking up time processing when I don't need it (my LCD will have multiple screens, so I only need it to be calculated when the LCD is in that particular state).

I've gotten it to display, and using this code results in the seconds counting up from 0 to 32 and then suddenly switching from 32 to -32 and counting up to 0 and starting over again. The minutes just display 0.

Any suggestions? Thanks for your help!

2

32 - big clue.
You're using "int"s to count milliseconds, and an "int" can store the range -32768 to + 32767

(I confess, I didn't read your code)

3

Thanks. I can't believe I didn't remember that... That was my problem. I'm using longs now instead of ints

4

If you look at the documentation for the millis function, you will see that the correct type (the return type for the millis() function) is unsigned long, not long.