Demo 44: Play "Happy Birthday" by ESP with Sigma-delta Modulation

1. Introduction
In this post, we will play "Happy Birthday" melody by ESP with Sigma-delta Modulation. Actually, you can use "digitalWrite" but Sigma-delta Modulation make the output smoother.
The mechanism to play melody you can find here.
2. Hardware

We will use cheap Audio Power Amplifier LM386 to aplify the melody.

Figure: LM386 Low Voltage Audio Power Amplifier

Pins are connected as:
ESP32 G27 connect LM386 IN
ESP32 5V (or 3.3 V) connect LM386 Vcc
ESP32 GND connect LM386 GND
3. Software
In order to use Sigma-delta Modulation in ESP please refer this.
Here is the full source code:

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int speakerPin = 27; //"happy birthday melody notes" char notes[] = "GGAGcB GGAGdc GGxecBA yyecdc"; int beats[] = { 2, 2, 8, 8, 8, 16, 1, 8, 2, 8, 8, 8, 16, 1, 2, 2, 8, 8, 8, 8, 16, 1, 8, 2, 8, 8, 8, 16 }; void playTone(int tone) { for (long i = 0; i < 100; i++) { sigmaDeltaWrite(0, 0); delayMicroseconds(tone); sigmaDeltaWrite(0, 100); delayMicroseconds(tone); } } void playNote(char note) { //notes char note_name[] = {'C', 'D', 'E', 'F', 'G', 'A', 'B', 'c', 'd', 'e', 'f', 'g', 'a', 'b', 'x', 'y' }; int timeHigh[] = { 1915, 1700, 1519, 1432, 1275, 1136, 1014, 956, 834, 765, 593, 468, 346, 224, 655 , 715 }; // play the tone corresponding to the note name for (int i = 0; i < sizeof(note_name); i++) { if (note_name[i] == note) { playTone(timeHigh[i]); } } } void setup() { sigmaDeltaSetup(0, 12000); //attach pin speakerPin to channel 0 sigmaDeltaAttachPin(speakerPin, 0); //initialize channel 0 to off sigmaDeltaWrite(0, 0); } void loop() { for (int i = 0; i < strlen(notes); i++) { // space is rest note if (notes[i] == ' ') { delay(beats[i] * 100); } else { playNote(notes[i]); } // pause between notes delay(100); } }