Arduino timer - convert millis() to days:hours:min

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

I've been trying to get a timer for my project that would convert millis() to days:hours:minutes:seconds. Here is what I did. It works well I think. I borrowed a little utility function to print colons and zeros from DateTime library/example.

Problems I see: I read arduino's 1000 millis is not actually 1 second... so the long ints for day hour etc may have to be recalculated.

Another thing is the millis() rollover... how do we incorporate Faludi's code into this? http://www.faludi.com/2007/12/18/arduino-millis-rollover-handling/
???

Let me know what you think, or if this has been done before hehe... and I just wasted 20 minutes of my life! ehh, it was fun so no biggie if that's the case.

 long day = 86400000; // 86400000 milliseconds in a day
 long hour = 3600000; // 3600000 milliseconds in an hour
 long minute = 60000; // 60000 milliseconds in a minute
 long second =  1000; // 1000 milliseconds in a second

void setup(){
 Serial.begin (57600); 
}

void loop(){
  time();
  delay(1000);
}

void time(){
 long timeNow = millis();
  
 int days = timeNow / day ;                                //number of days
 int hours = (timeNow % day) / hour;                       //the remainder from days division (in milliseconds) divided by hours, this gives the full hours
 int minutes = ((timeNow % day) % hour) / minute ;         //and so on...
 int seconds = (((timeNow % day) % hour) % minute) / second;
 
  // digital clock display of current time
  Serial.print(days,DEC);  
  printDigits(hours);  
  printDigits(minutes);
  printDigits(seconds);
  Serial.println();  
  
}

void printDigits(byte digits){
  // utility function for digital clock display: prints colon and leading 0
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits,DEC);   
}
2

why do you think that 1000 millis is not actually a second?

FWIW, here is a version of your sketch implimented with the macros from DateTime.h. It uses a little less flash and RAM because it uses fewer variables.

// macros from DateTime.h 
/* Useful Constants */
#define SECS_PER_MIN  (60UL)
#define SECS_PER_HOUR (3600UL)
#define SECS_PER_DAY  (SECS_PER_HOUR * 24L)
 
/* Useful Macros for getting elapsed time */
#define numberOfSeconds(_time_) (_time_ % SECS_PER_MIN)  
#define numberOfMinutes(_time_) ((_time_ / SECS_PER_MIN) % SECS_PER_MIN) 
#define numberOfHours(_time_) (( _time_% SECS_PER_DAY) / SECS_PER_HOUR)
#define elapsedDays(_time_) ( _time_ / SECS_PER_DAY)  

void setup(){
 Serial.begin (57600);
}

void loop(){  
  time(millis() / 1000);
  delay(1000);
}

void time(long val){  
 int days = elapsedDays(val);
 int hours = numberOfHours(val);
 int minutes = numberOfMinutes(val);
 int seconds = numberOfSeconds(val);

  // digital clock display of current time
  Serial.print(days,DEC);  
  printDigits(hours);  
  printDigits(minutes);
  printDigits(seconds);
  Serial.println();  
  
}

void printDigits(byte digits){
  // utility function for digital clock display: prints colon and leading 0
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits,DEC);  
}
1 Like
3

Mem, awsome. How would you incorporate the rollover? does the rollover still take place since (I presume) we're using the clock cycles? it does rollover correct?

4

Yes, millis will rollover. If you want to avoid this, the easiest way is to use Datetime

#include <DateTime.h>

void setup(){
 Serial.begin (57600);
 DateTime.sync(0); // start the clock
}

void loop(){  
  time(DateTime.now());
  delay(1000);
}

void time(long val){  
 int days = elapsedDays(val);
 int hours = numberOfHours(val);
 int minutes = numberOfMinutes(val);
 int seconds = numberOfSeconds(val);

  // digital clock display of current time
  Serial.print(days,DEC);  
  printDigits(hours);  
  printDigits(minutes);
  printDigits(seconds);
  Serial.println();  
  
}

void printDigits(byte digits){
  // utility function for digital clock display: prints colon and leading 0
  Serial.print(":");
  if(digits < 10)
    Serial.print('0');
  Serial.print(digits,DEC);  
}

This won't roll over until 2038

1 Like