Module 3: Sound

Sounds On The Y-Badge

Y-Badge v3 has a speaker and Y-Badge v2 has a buzzer. Both can be used to play sounds. The speaker is able to play a wider range of sounds, but the buzzer is simpler to use. Both are able to play sounds by turning an electromagnet on and off at high speeds. The magnetic field that is produced vibrates a small disk very quickly, creating the sound you hear. We can specify the frequency of the buzzer in order to play different notes, and how long that note is played for.

Y-Board v2 Buzzer. Y-Board v3 has a speaker.

Functions

You can also play a sequence of notes by using the following functions (either blocking, or in the background)

Yboard.play_notes(<string>);
Yboard.play_notes_background(<string>);

The text string supports the following characters:

Character	Description
A–G	Specifies a note that will be played.
R	Specifies a rest (no sound for the duration of the note).
+ or # after a note	Raises the preceding note one half-step (sharp).
- after a note	Lowers the preceding note one half-step.
> after a note	Plays the note one octave higher (multiple >’s can be used, eg: C»)
< after a note	Plays the note one octave lower (multiple <’s can be used, eg: C«)
1–2000 after a note	Determines the duration of the preceding note. For example, C16 specifies C played as a sixteenth note, B1 is B played as a whole note. If no duration is specified, the note is played as a quarter note.
. after a note	“Dots” increase the length by 50%. Each additional dot adds half as much as the previous dot, so that “A..” is 1.75 times the length of “A”.
O followed by a #	Changes the octave. Valid range is 4-7. Default is 5.
T followed by a #	Changes the tempo. Valid range is 40-240. Default is 120.
V followed by a #	Changes the volume. Valid range is 1-10. Default is 5.
!	Resets octave, tempo, and volume to default values.
spaces	Spaces can be placed between notes or commands for readability, but not within a note or command (eg: `"C4# D4"` is valid, `"C 4 # D 4"` is not. `"T120 A B C"` is valid, `"T 120 A B C"` is not).

Checking if the Sound is Done

The following function will return true if the sounds is still playing, and false if it is done:

Yboard.is_audio_playing();

You may need to learn about loops and conditional statements before you can use this function in your code.

Examples

To play “Twinkle Twinkle Little Star” using Octave 4 and 180 beats per minute, you could use the following code:

Yboard.play_notes("O4 T180 CCGGAAG2 FFEEDDC2");

Exploration

Remember to change main.cpp before continuing…

📝 NOTE: You will need to go to main.cpp and change the comments to call the correct activity function:
// delay_activity();
sound_activity();

Make the speaker play a C note for 3 seconds and then stop.
Make the speaker play C, D, E, D, C for 500ms each.
What happens if you try to call Yboard.set_led_color(1, 255, 0, 0) to turn LED 1 red right after you call Yboard.play_notes_background("C") to play middle C for 1 seconds? Does the board wait to turn the light on until the sound is done playing?

Why Does This Happen?

The Yboard.play_notes_background() function is a non-blocking function, which means other functions that are called after it will actually run at the same time. However, the speaker can only play one note at a time, so any additional Yboard.play_notes_background() calls will wait until the one before has finished.
Play a scale of notes in Octave 5. Then play the same scale in Octave 6, but at double the tempo.

Challenges

Remember to comment/uncomment the correct function calls…

Remember to comment out the sound_exploration(); call in the sound_activity function and uncomment the correct challenge function:

sound_exploration();
// sound_challenge1();
// sound_challenge2();

Challenge 1: Experiment with the durations of the above song to add some rythm or adjust the speed of the song. How long the notes are played in comparison to each other can change how the song sounds (note how some notes are played twice as long as others above). Can you make the song twice as fast?

Challenge 2: Finish the rest of “Twinkle Twinkle Little Star” by adding more to the code.

Challenge 3: Look up the notes to a song you like and try to play it on the Y-Board. You can use the play_notes function to play the song in the background while you do other things.