micros() max value before overflow

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hello, i need to know the micros() biggest value before overflow, so I can implement an "asincronous" pulseIn(), and also "pulseOut()".
I don't much precision for the length of pulse, +-100microsec is enough, but it has to be fast.

2

http://arduino.cc/en/Reference/Micros

3

Unsigned long variables are extended size variables for number storage, and store 32 bits (4 bytes). Unlike standard longs unsigned longs won't store negative numbers, making their range from 0 to 4,294,967,295 (2^32 - 1).

From http://arduino.cc/en/Reference/UnsignedLong

4

Are you sure micros() will use all unsigned long values?
btw thank you ;D

5

Use the Source, Luke.

volatile [glow]unsigned long[/glow] timer0_overflow_count ;
...
[glow]unsigned long[/glow] micros() {
...
m = timer0_overflow_count;
...
}

That should remove all doubt.

Korman

6

Are you sure micros() will use all unsigned long values?

The value returned by micros is always evenly divisible by four. (At least that's what I remember)

7

The value returned by micros is always evenly divisible by four.

... on Arduino with a 16MHz CPU. On 8MHz CPU it will be evenly divisible by 8.

Korman