Arduino uptime howto

src:
http://forum.arduino.cc/index.php/topic,44030.0.html
http://playground.arduino.cc/Main/MsTimer2

notes:


------------
// Uptime counter
#include <MsTimer2.h>

volatile unsigned long _Uptime =0;

void updateuptime() {
_Uptime++;
}

unsigned long getUpTime()
{
    unsigned long ret;
    // optional: disable interrupts
    cli();
    ret = _Uptime;
    // optional: enable interrupts 
    sei();
    return ret;
}

void setup() {
  MsTimer2::set(1000, updateuptime); 
  MsTimer2::start();
}

void loop() {
   // call getUpTime here.
}