Characteristic	Locus
Inheritance	System.Object > PiezoSpeaker
Namespace	Meadow.Foundation.Audio
Assembly	Meadow.Foundation.dll

Syntax

public class PiezoSpeaker : IToneGenerator

Remarks

The PiezoSpeaker class represents a simple piezo speaker that can be used to generate tones across a range of frequencies. They typically perform well between 1-5kHz but may go as high as 100kHz. Implements IToneGenerator.

The positive pin of the piezo speaker connects to a PWM capable pin on the Meadow and the negative pin connects to common/ground. A resistor can be placed in-line to reduce volume.

Examples

The following example shows how to initialize a PiezoSpeaker and play a melody using an array of notes:

using System.Threading;
using Meadow;
using Meadow.Devices;
using Meadow.Foundation.Audio;

namespace PiezoSpeaker_Sample
{
    public class Program
    {
        static IApp app;
        public static void Main(string[] args)
        {
            if (args.Length > 0 && args[0] == "--exitOnDebug") return;

            // instantiate and run new meadow app
            app = new MeadowApp();
        }
    }

    public class MeadowApp : App<F7Micro, MeadowApp>
    {
        const int NUMBER_OF_NOTES = 16;
        float[] melody;

        public MeadowApp()
        {
            melody = new float[NUMBER_OF_NOTES]
            {
                NoteFrequencies.NOTE_A3,
                NoteFrequencies.NOTE_B3,
                NoteFrequencies.NOTE_CS4,
                NoteFrequencies.NOTE_D4,
                NoteFrequencies.NOTE_E4,
                NoteFrequencies.NOTE_FS4,
                NoteFrequencies.NOTE_GS4,
                NoteFrequencies.NOTE_A4,
                NoteFrequencies.NOTE_A4,
                NoteFrequencies.NOTE_GS4,
                NoteFrequencies.NOTE_FS4,
                NoteFrequencies.NOTE_E4,
                NoteFrequencies.NOTE_D4,
                NoteFrequencies.NOTE_CS4,
                NoteFrequencies.NOTE_B3,
                NoteFrequencies.NOTE_A3,
            };

            var piezo = new PiezoSpeaker(Device.CreatePwmPort(Device.Pins.D10));

            while (true)
            {
                for (int i = 0; i < NUMBER_OF_NOTES; i++)
                {
                    //PlayTone with a duration in synchronous
                    piezo.PlayTone(melody[i], 600);
                    Thread.Sleep(50);
                }

                Thread.Sleep(1000);

                //PlayTone without a duration will return immediately and play the tone
                piezo.PlayTone(NoteFrequencies.NOTE_A4);
                Thread.Sleep(2000);

                //call StopTone to end a tone started without a duration
                piezo.StopTone();

                Thread.Sleep(2000);
            }
        }
    }

    public static class NoteFrequencies
    {
        public const float NOTE_A3  = 220;
        public const float NOTE_B3  = 247;
        public const float NOTE_CS4 = 277;
        public const float NOTE_D4  = 294;
        public const float NOTE_E4  = 330;
        public const float NOTE_FS4 = 370;
        public const float NOTE_GS4 = 415;
        public const float NOTE_A4  = 440;
    }
}

Example Circuit

Constructors

PiezoSpeaker(IIODevice, IPin, Single, Single)

Create a new PiezoSpeaker instance

Declaration

public PiezoSpeaker(IIODevice device, IPin pin, float frequency = 100F, float dutyCycle = 0F)

Parameters

Type	Name	Description
IIODevice	device
IPin	pin	PWM Pin connected to the PiezoSpeaker
System.Single	frequency
System.Single	dutyCycle

PiezoSpeaker(IPwmPort)

Create a new PiezoSpeaker instance

Declaration

public PiezoSpeaker(IPwmPort port)

Parameters

Type	Name	Description
IPwmPort	port

Properties

Port

Gets the port that is driving the Piezo Speaker

Declaration

public IPwmPort Port { get; protected set; }

Property Value

Type	Description
IPwmPort

Methods

PlayTone(Single, Int32)

Play a frequency for a specified duration

Declaration

public void PlayTone(float frequency, int duration = 0)

Parameters

Type	Name	Description
System.Single	frequency	The frequency in hertz of the tone to be played
System.Int32	duration	How long the note is played in milliseconds, if durration is 0, tone plays indefinitely

StopTone()

Stops a tone playing

Declaration

public void StopTone()