using timer interrupt

Projects Programming
1

if i want to use timer interrupt on arduino uno, is there any pin i shouldn't use? the pin that belongs to the timer on the ATmega.. is that correct or i just can use all pin and the timer as well?

fyi, my program uses digital pin 0-11 and i want to use timer 2 interrupt.. i've downloaded the MsTimer2 lib from arduino playground, and i still can't use it.. any suggestion??

my code

void loop()
{
  MsTimer2::set(500, timing);
  MsTimer2::start();
  
    if (Serial.available()>0)
  {
   // digitalWrite(LED, HIGH);
    serial=Serial.read();
    if (serial=='w'){
      maju();
    } else if (serial=='d'){
      kanan();
    } else if (serial=='a'){
      kiri();
    } else if (serial=='s'){
      mundur();
    } else {
      selesai();
    }
  }
}

void timing(){
  ultrasonic();
    //motor();
    IR();
    printing();
    compass();  
}

i had a very long code, i think this is the only part where i use the timer.. any help would be appreciated ^^ thankss..

2 
void loop()
{
  MsTimer2::set(500, timing);
  MsTimer2::start();

Why are you restarting the timer on every pass through loop()?

What do all those functions in the timing() function do? Will they be done when the interrupt fires again?

3

you can only have two interrupts on a UNO

digital pin 2 and 3 are used for interupts 0 and 1

other boards may have more interrupts - not sure

4

you can only have two interrupts on a UNO

You can only have two external interrupts. You can have any number of other kinds of interrupts, such as timer interrupts.