Fourth button Binary Conversion Not working

Question

I'm going through the Inventor's Kit from Sparkfun, specifically around the Digital Trumpet. To expand on the project I'm adding a fourth button and trying to turn the buttons pressed into a binary number to give myself 16 notes from 4 buttons. Here's my code:

using namespace std;

//set the pins for the button and buzzer
int firstKeyPin = 2;
int secondKeyPin = 3;
int thirdKeyPin = 4;
int fourthKeyPin = 7;

int buzzerPin = 10;

void setup() {
  Serial.begin(9600);           //start a serial connection with the computer
  
  //set the button pins as inputs
  pinMode(firstKeyPin, INPUT_PULLUP);
  pinMode(secondKeyPin, INPUT_PULLUP);
  pinMode(thirdKeyPin, INPUT_PULLUP);
  pinMode(fourthKeyPin, INPUT_PULLUP);


  //set the buzzer pin as an output
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  auto toneTot = 0b0;
  
  if (digitalRead(firstKeyPin) == LOW) {
    tone(buzzerPin, 262);                     //play the frequency for c
    toneTot |= 1;
  }
  if (digitalRead(secondKeyPin) == LOW) {
    tone(buzzerPin, 330);                     //play the frequency for e
    toneTot |= 10;
  }
  if (digitalRead(thirdKeyPin) == LOW) { //if the third key is pressed
    tone(buzzerPin, 392);                     //play the frequency for g
    toneTot |= 100;
  }
  if (digitalRead(fourthKeyPin) == LOW) { //if the fourth key is pressed
    tone(buzzerPin, 494);
    toneTot |= 1000;
  }

  Serial.println("Binary collected");
  Serial.println(String(toneTot));
}

In general this has worked perfectly fine, except for the behavior of the 4th button. I've tried moving buttons around, switching pins, etc, but it keeps on working so that when a 4th button is pressed instead of values like 1001, 1010, 1011, etc, it comes out like 1002 and 1004

Answer 1

Here:

  toneTot |= 10;

you are writing 10 decimal to toneTot which means you are not only setting bit 1, as you expected. 10d is similar to 0b00001010, so you are setting bit 3 and bit 1. Switch it to:

toneTot |= 0x02;

or

toneTot |= 0b00000010;

to only set bit 1.

Same think for the other bits set in toneTot.