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PWM melody

This example is similar to the previous one. You will make the buzzer to play a small piece of music.

What you need​

  • SwiftIO Micro (or SwiftIO board)
  • Breadboard
  • Buzzer
  • Jumper wires

Circuit​

  1. Plug the buzzer onto the breadboard.
  2. Connect any one leg to the pin GND and the other to the pin PWM0A.
circuit diagram

Example code​

Open the project PWMMelody in the folder MadExamples/Examples/SimpleIO if you downloaded the examples.

PWMMelody.swift
// 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
import MadBoard

@main
public struct PWMMelody {
    public static func main() {
        // Initialize a PWM output pin that the speaker is connected to.
        let speaker = PWMOut(Id.PWM0A)

        // Specify several frequencies corresponding to each note of the melody. 
        let frequencies = [
            330, 330, 349, 392,
            392, 349, 330, 294,
            262, 262, 294, 330,
            330, 294, 294
        ]

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

Code analysis​

let frequencies = [
    330, 330, 349, 392,
    392, 349, 330, 294,
    262, 262, 294, 330,
    330, 294, 294
]

The frequencies on the array correspond to the notes of the music. If you want to play other music, you can replace the frequencies according to the music score.

Reference​

PWMOut - set the PWM signal.

MadBoard - find the corresponding pin id of your board.