millis() vs creating a "long" variable

Question

I think my issue is not fully understanding how the millis() function works;

I am wondering the difference between simply creating a variable such as

long fake_millis ++ ; 

vs using millis()?

• sa_leinad: millis() returns an unsigned long, not a long. It is never negative.
• Edgar Bonet: Besides the unsigned issue, how would you manage to do fake_millis++; exactly once per millisecond? Think about it: it's not so simple, especially if the program is busy doing other stuff. Best solution would be to do it from a timer interrupt. Once you do that, you have essentially reimplemented millis().

Answer 1

millis() returns the ACTUAL time milliseconds since the start of the program. Wheter you put a delay, you do multiple tasks, millis() will still return the right time.

The other method that you mentionned will not work if, for example, you add a delay in the program. Then, for more complex tasks that might take more time, your "custom" counter will be very unacurate.

I short, just use millis(). It is easy to use and works great.

P.S. Use an unsigned long instead of a long.

• danieljay: appreciate the response. I am wondering though for this basic formula where i just need to have a "second" counter, pastebin.com/raw/hxcVukR7 could i just replace Millis() with my method ?
• Dat Ha: @danieljay, for that simple example, maybe, but for more complex programs, stick with millis()