SparkFun Inventor's Kit for Photon Experiment Guide

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Experiment 5: Music Time

Introduction

In this circuit, we’ll again bridge the gap between the digital world and the analog world. We’ll be using a piezo speaker that makes a small “click” when you apply voltage to it (try it!). By itself that isn’t terribly exciting, but if you turn the voltage on and off hundreds of times a second, the piezo speaker will produce a tone. And if you string a bunch of tones together, you’ve got music! This circuit and sketch will play a classic tune. We’ll never let you down!

Parts Needed

You will need the following parts:

  • Photon RedBoard, Breadboard, and Base Plate
  • 1x Piezo Speaker
  • 2x Jumper Wires
Using a Photon by Particle instead or you don't have the kit? No worries! You can still have fun and follow along with this experiment. We suggest using the parts below:
Mini Speaker - PC Mount 12mm 2.048kHz

COM-07950
1.95
5
Jumper Wires - Connected 6" (M/M, 20 pack)

PRT-12795
1.95
2

Suggested Reading

  • tone() – Read up about tone() to get started on making your own songs!

Let’s Talk More about Polarity

We talked about polarity shortly in the past experiments. In the realm of electronics, polarity indicates whether a circuit component is symmetric or not. A non-polarized component – a part without polarity – can be connected in any direction and still function the way it’s supposed to function. A symmetric component rarely has more than two terminals, and every terminal on the component is equivalent. You can connect a non-polarized component in any direction, and it’ll function just the same.

A polarized component – a part with polarity – can only be connected to a circuit in one direction. A polarized component might have two, twenty, or even two-hundred pins, and each one has a unique function and/or position. If a polarized component was connected to a circuit incorrectly, at best it won’t work as intended. At worst, an incorrectly connected polarized component will smoke, spark, and be one very dead part.

To learn more about polarity, check out our What is Polarity? tutorial!

Hardware Hookup

If the piezo speaker doesn’t easily fit into the holes on the breadboard, try rotating it slightly.

Pay special attention to the component’s markings indicating how to place it on the breadboard. Polarized components can only be connected to a circuit in one direction. Orientation matters for the following component: Piezo Speaker. It's hard to tell which pin is '+' and which is '-' from the image below. The buzzer should have a tiny '+' simbol on one of the pins. This pin should be connected to pin 2, and the other pin should go to GND.

RedBoard piezo speaker hookup

Having a hard time seeing the circuit? Click on the Fritzing diagram to see a bigger image.

Photon Code

language:c
/*  SparkFun Inventor's Kit for Photon
    Experiment 5 - Part 1: Music Time
    This sketch was written by SparkFun Electronics
    August 31, 2015
    https://github.com/sparkfun/Inventors_Kit_For_Photon_Experiments

    This application plays Rick Astley - Never Gonna Give You Up song
    Development environment specifics:
    Particle Build environment (https://www.particle.io/build)
    Particle Photon RedBoard
    Released under the MIT License (http://opensource.org/licenses/MIT)
*/

const int speakerPin = D2;

// We'll set up an array with the notes we want to play
// change these values to make different songs!

// Length must equal the total number of notes and spaces 

const int songLength = 18;

// Notes is an array of text characters corresponding to the notes
// in your song. A space represents a rest (no tone)

char notes[] = "cdfda ag cdfdg gf "; // a space represents a rest

// Beats is an array of values for each note and rest.
// A "1" represents a quarter-note, 2 a half-note, etc.
// Don't forget that the rests (spaces) need a length as well.

int beats[] = {1,1,1,1,1,1,4,4,2,1,1,1,1,1,1,4,4,2};

// The tempo is how fast to play the song.
// To make the song play faster, decrease this value.

int tempo = 150;


void setup() 
{
  pinMode(speakerPin, OUTPUT);

  // We only want to play the song once, so we'll put it in the setup loop
  int i, duration;

  for (i = 0; i < songLength; i++) // step through the song arrays
  {
    duration = beats[i] * tempo;  // length of note/rest in ms

    if (notes[i] == ' ')          // is this a rest? 
    {
      delay(duration);            // then pause for a moment
    }
    else                          // otherwise, play the note
    {
      tone(speakerPin, frequency(notes[i]), duration);
      delay(duration);            // wait for tone to finish
    }
    delay(tempo/10);              // brief pause between notes
  }

  //If you want your song to loop forever, place that code in the loop() below. 
}


void loop() 
{
//do nothing 
}


int frequency(char note) 
{
  // This function takes a note character (a-g), and returns the
  // corresponding frequency in Hz for the tone() function.

  int i;
  const int numNotes = 8;  // number of notes we're storing

  // The following arrays hold the note characters and their
  // corresponding frequencies. The last "C" note is uppercase
  // to separate it from the first lowercase "c". If you want to
  // add more notes, you'll need to use unique characters.

  // For the "char" (character) type, we put single characters
  // in single quotes.

  char names[] = { 'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C' };
  int frequencies[] = {262, 294, 330, 349, 392, 440, 494, 523};

  // Now we'll search through the letters in the array, and if
  // we find it, we'll return the frequency for that note.

  for (i = 0; i < numNotes; i++)  // Step through the notes
  {
    if (names[i] == note)         // Is this the one?
    {
      return(frequencies[i]);     // Yes! Return the frequency
    }
  }
  return(0);  // We looked through everything and didn't find it,
              // but we still need to return a value, so return 0.
}

What You Should See

You should see - well, nothing! But you should be able to hear a song. If it isn’t working, make sure you have assembled the circuit correctly and verified and uploaded the code to your board or see the troubleshooting section.

Photon RedBoard piezo speaker

See if you can recreate your favorite songs!

Code to Note

Up until now we’ve been working solely with numerical data, but the Photon RedBoard can also work with text. Characters (single, printable, letters, numbers and other symbols) have their own type, called “char”. When you have an array of characters, it can be defined between double-quotes (also called a “string”), OR as a list of single-quoted characters.

tone(pin, frequency, duration);

One of Photon RedBoard’s many useful built-in commands is the tone() function. This function drives an output pin at a certain frequency, making it perfect for driving piezo speakers. If you give it a duration (in milliseconds), it will play the tone then stop. If you don’t give it a duration, it will keep playing the tone forever (but you can stop it with another function, noTone() ).

Troubleshooting

  • No Sound - Given the size and shape of the piezo buzzer it is easy to miss the right holes on the breadboard. Try double checking its placement.

  • Can’t Think While the Melody is Playing - Just pull up the piezo buzzer whilst you think, upload your program then plug it back in.

  • Feeling Let Down and Deserted - The code is written so you can easily add your own songs.