Software timer not working

Using Arduino Programming Questions
#1

Hi, I’m having a problem envolving arduino’s (both uno and due) timer and a software timer I made.
I made this code to isolate the problem:

#include <TimerOne.h>

typedef uint32_t mod_timer_t;

/*
************************************************************************************************************************
Software Timer implementation. It works like this: When I instantiate an STimer,
I set its period on the constructor call. There is this static_timer_count which is 
incremented each timer interruption. When I start a implementation of STimer,
the object will save (in offset variable) the current value of static_timer_count.
When I call check(), the difference between static_timer_count and offset is compared
to period, If its bigger or equal, true is returned, otherwise, false is returned. 
************************************************************************************************************************
*/
class STimer
{
public:

	static mod_timer_t static_timer_count;

	mod_timer_t period = 1; //in ms
	mod_timer_t offset = 0;
	bool working = false;

	STimer(mod_timer_t period){ //period in milisseconds
		this->period = period;
	}

	void reset(){
		working = true;
		offset = static_timer_count;
	}

	bool check(){ // tells if the timer reached its period
		if(working){
			if((mod_timer_t)(static_timer_count - offset) >= period){
				offset = static_timer_count;
				return true;
			}
		}
		return false;
	}
};

// static_timer_count initialization.
mod_timer_t STimer::static_timer_count = 0;

//STimer implementation.
STimer alarm(1000);

// holds led position, HIGH or LOW.
bool led_position = false;

// similar to led position
bool togg = false;

void isr_timer(){
	STimer::static_timer_count++;

	// this is for check on osciloscope. Its working.
	togg ^= 1;
	digitalWrite(12, togg);
}

void setup(){
	pinMode(13, OUTPUT);
	pinMode(12, OUTPUT);

	Timer1.initialize(1000);
	Timer1.attachInterrupt(isr_timer);

	alarm.reset();
}

void loop(){
	// this while holds the execution until alarm set off.
	while(!(alarm.check()));

	// when alarm sets off, the led_position is inverted and the led shall blink.
	led_position ^= 1;
	digitalWrite(13, led_position);
	alarm.reset();

}

This code doesn’t work. The strange part is that if I change this loop for this, It works!!

void loop(){
	 if(alarm.check()){
		led_position ^= 1;
		digitalWrite(13, led_position);
		alarm.reset();
	 }
}

Any Ideas of what could make this happen? Just to remember, I tested this with both Uno and Due timers.

#2

Also, i tested this class on my computer (linux) using interrupts and it worked.

#3 
void loop(){
	// this while holds the execution until alarm set off.
	while(!(alarm.check()));

This will do nothing either way. The semicolon terminates the statement.

#4

Your posted code does not compile.

sketch_sep27a:21: error: ISO C++ forbids initialization of member ‘period’
sketch_sep27a:21: error: making ‘period’ static
sketch_sep27a:21: error: ISO C++ forbids in-class initialization of non-const static member ‘period’
sketch_sep27a:22: error: ISO C++ forbids initialization of member ‘offset’
sketch_sep27a:22: error: making ‘offset’ static
sketch_sep27a:22: error: ISO C++ forbids in-class initialization of non-const static member ‘offset’
sketch_sep27a:23: error: ISO C++ forbids initialization of member ‘working’
sketch_sep27a:23: error: making ‘working’ static
sketch_sep27a:23: error: ISO C++ forbids in-class initialization of non-const static member ‘working’
#5

Variables shared with an ISR should be volatile:

class STimer
{
public:

	volatile static mod_timer_t static_timer_count;

...

// static_timer_count initialization.
volatile mod_timer_t STimer::static_timer_count = 0;

Adding that in, it seems to work.

#6

It worked ! Thanks Nick!

#7