Overflow, does it matter?

Projects Programming
1

If i want to print value once a second far to the future is this OK for it:

Light1 = analogRead(LDR1); 

if (TimeNow > PrintTime)
{
  Serial.println(Light1);
  PrintTime = (TimeNow + 1000);
}

TimeNow = millis();

There will be value overflow sometimes (in every 70 min or what was that)
but does it actually matter in this use ? Or is there easy "proper" way to print it with few lines ?

(PrintTime is also unsigned long, like millis() is)

2

A subtraction should always be used so the roll-over will have no effect. Here is a rather long posting on the subject:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1260223964/1

3

There will be value overflow sometimes (in every 70 min or what was that)

sp. "every 49 days"

4

is this OK for it:

No. Subtraction s safe. Addition is not.

if(TimeNow - PrintTime > 1000)
{
   // print...
   PrintTime = TimeNow;
}

There will be value overflow sometimes (in every 70 min or what was that)

millis() overflows in about 49 days. micros() overflows in about 70 minutes.

5

Of course it should be done by sutracting ! Thanks for fast replies !

little messed millis and micros too :roll_eyes: