# Variable optimized away?

I have a sketch that isn’t working correctly. There is a test (justpressed) that is not working correctly. It is always testing as true when in fact it is false. I loaded the sketch in to an AVR Compiler and got the same results but it has a Watch window and an immediate window (is there something similar for Arduino?) and when I got to justpressed it showed i as being optimized away and if I plug in justpressed I get the message optimized away. If I change the settings to no optimization, then It runs properly… Any idea why this would happen?

``````#define DEBOUNCE 10  // button debouncer, how many ms to debounce, 5+ ms is usually plenty

byte buttons[] = {21, 22, 23, 24, 25, 26, 27, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40}; // the pin #s of the buttons
// This handy macro lets us determine how big the array up above is, by checking the size
#define NUMBUTTONS sizeof(buttons)

byte LEDs[]={0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20}; //the pin #s of LED pins
boolean LEDState[NUMBUTTONS]={}; //keep track of LED state Set all to False
int LEDOn=0; //to keep track of how many LEDs are currently lit....Do we need? check array?
byte combo1[]={0,1,2,3,4}; // The buttons that make up the combination in the first puzzle
byte combo2[]={13,14,15,16}; // The buttons that make up the combination in the second puzzle

// we will track if a button is just pressed, just released, or 'currently pressed'
byte pressed[NUMBUTTONS]={}, justpressed[NUMBUTTONS]={}, justreleased[NUMBUTTONS]={};

void setup() {
byte i;

// Set LEDs pins as out put and turn off
for(int i=0; i < NUMBUTTONS; i++)
{
pinMode(LEDs[i], OUTPUT);
digitalWrite(LEDs[i], LOW);
}

// Make button pins as input & enable pull-up resistors on switch pins
for (i=0; i < NUMBUTTONS; i++)
{
pinMode(buttons[i], INPUT_PULLUP);
digitalWrite(buttons[i], HIGH);
}

// Run timer2 interrupt every 15 ms
TCCR2A = 0;
TCCR2B = 1<<CS22 | 1<<CS21 | 1<<CS20; //1024 prescaler

//Timer2 Overflow Interrupt Enable
TIMSK2 |= 1<<TOIE2;

}

SIGNAL(TIMER2_OVF_vect) {
check_switches();
}

void check_switches()
{
static byte previousstate[NUMBUTTONS];
static byte currentstate[NUMBUTTONS];
static long lasttime;
byte index;

if (millis() < lasttime){ // we wrapped around, lets just try again
lasttime = millis();
}

if ((lasttime + DEBOUNCE) > millis()) {
// not enough time has passed to debounce
return;
}
// ok we have waited DEBOUNCE milliseconds, lets reset the timer
lasttime = millis();

for (index = 0; index < NUMBUTTONS; index++){

/*
Serial.print(index, DEC);
Serial.print(": cstate=");
Serial.print(currentstate[index], DEC);
Serial.print(", pstate=");
Serial.print(previousstate[index], DEC);
Serial.print(", press=");
*/

if (currentstate[index] == previousstate[index]) {
if ((pressed[index] == LOW) && (currentstate[index] == LOW)) {
// just pressed
justpressed[index] = 1;
}
else if ((pressed[index] == HIGH) && (currentstate[index] == HIGH)) {
// just released
justreleased[index] = 1;
}
pressed[index] = !currentstate[index];  // remember, digital HIGH means NOT pressed
}
//Serial.println(pressed[index], DEC);
previousstate[index] = currentstate[index];   // keep a running tally of the buttons
}
}

void loop() {
byte numOn=0;
byte comboCheck=0;
for (byte i = 0; i < 12; i++){ //only check first 12 buttons

if (justpressed[i]) {
justpressed[i] = 0;
LEDState[i]=!LEDState[i]; //toggle LED Status
for (byte j =0; j < 12; j++) { //count the number of LEDs lit
if (LEDState[j]) {
numOn++;
}
}
if (numOn==5){
for (byte i=0; i<5; i++){
if (LEDState[combo1[i]])
comboCheck++;
}
if (comboCheck==5){// Correct combo reached
// to do
}
else {// wrong combo
for (int i = 0; i< 12; i++){
digitalWrite(LEDs[i],LOW);
LEDState[i]=false;
}
//Call second routine
}

}
}

}

}
``````

Make ALL the variables modified by the ISRs and shared with non-ISR code be "volatile."

``````volatile byte pressed[NUMBUTTONS]={}, justpressed[NUMBUTTONS]={}, justreleased[NUMBUTTONS]={};
``````
``````SIGNAL(TIMER2_OVF_vect) {
check_switches();
}
``````

Variables used in an ISR should be declared volatile.

And you don't escape from this rule by calling a function from the ISR.

westfw put it more accurately:

Make ALL the variables modified by the ISRs and shared with non-ISR code be "volatile."

What's this for

``````justpressed[NUMBUTTONS]={}
``````

If you don't want to initialise it, then don't.

``````justpressed[NUMBUTTONS];
``````

Volatile did the trick! Thanks!