Why doesn't pin 3 blink? It blinks in another program

Question

I used toneMelody example code (sketch sample 02.Digital->toneMelody) on an Arduino UNO. Then I wanted to blink an LED with the melody.

Here's the code:

#include "pitches.h"
#define BLUE 3 // pin 3 does not blink. but, pin 9 ok.
#define GREEN 5
#define RED 6

int melody[] = {
  NOTE_C4, NOTE_G3, NOTE_G3, NOTE_A3, NOTE_G3, 0, NOTE_B3, NOTE_C4
};    
int noteDurations[] = {
  4, 8, 8, 4, 4, 4, 4, 4
};

void setup() {
  for (int thisNote = 0; thisNote < 8; thisNote++) {
    analogWrite(RED, 0);
    analogWrite(GREEN, 0);
    analogWrite(BLUE, 0);
    int noteDuration = 1000 / noteDurations[thisNote];
    tone(8, melody[thisNote], noteDuration);    
    int pauseBetweenNotes = noteDuration * 1.30;
    int color = melody[thisNote] % 5;
    if(color == 0) {   
      analogWrite(RED, 200);
    } else if(color == 1) {   
      analogWrite(GREEN, 200);
    } else {
      analogWrite(BLUE, 200);
    }
    delay(pauseBetweenNotes);
    noTone(8);
  }
  analogWrite(RED, 0);
  analogWrite(GREEN, 0);
  analogWrite(BLUE, 0);
}

void loop() {
  // no need to repeat the melody.
}

Unfortunately, pin 3 did not blink. But it worked when I changed pin 3 to pin 9.

To check whether pin 3 or Blue LED is broken, I checked with the following code.

#define BLUE 3

void setup() {
  analogWrite(BLUE, 0);
}

void loop() {
  for(int i = 0 ; i < 255 ; i ++) {
    analogWrite(BLUE, i);
    delay(10);
  }    
  analogWrite(BLUE, 0);
}

This code worked. Blue LED blinked. Why couldn't pin 3 blink with toneMelody?

Thanks.

Answer 1

In the tone function reference you can read:

Use of the tone() function will interfere with PWM output on pins 3 and 11 (on boards other than the Mega).

analogWrite() is PWM