PWMMelody

This example shows how to use the PWMOut to generate notes. It plays a little melody which you may have heard before.

What you need

• SwiftIO board

• Jumper wires

• Piezo buzzer or a speaker

• SwiftIO shield (optional)

Circuit

Code

// Enable the speaker to play a simple melody by changing the frequency of PWM output.

// Import the library to enable the relevant classes and functions.
import SwiftIO

// Initialize a PWM output pin the speaker is connected to.
let speaker = PWMOut(Id.PWM2B)

// Specify several frequencies corresponding to each note of the melody. 
let fre = [
    350,350,393,441,
    441,393,350,330,
    294,294,330,350,
    350,330,330
]

/// Allow the speaker to repeat the melody again and again.
while true {
    for f in fre {
        // Change the frequency and the duty cycle of output to produce each note.
        speaker.set(frequency: f, dutycycle: 0.5)
        sleep(ms: 250)
    }
}

Instruction

The code above uses a Frequency as musical pitches. For example, NOTE_C4 is middle C, whose frequency is 262 Hz. Latter example MidiPlayer we will markdown all this musical note in a file. This file contains all the pitch values for typical notes. You may find it useful whenever you want to make musical notes.

See Also

• PWMOut - The PWMOut class is used to change the time of high voltage during one period to simulate different output.

References

• Frequency and Pitch
• Online Tone Generator
• wiki: Pitch (music)