5:Make PU Talk via pxt-billy

Lesson: Giving PU Robot a Voice

In this lesson, we will transform PU Robot from a silent dancer into a talking companion! You will learn how to install a “speech engine” and use a clever script to make PU say something new every time you press a button.

Knowledge: https://makecode.microbit.org/types/string https://makecode.microbit.org/reference/text https://github.com/adamish/pxt-billy https://ia803202.us.archive.org/30/items/user_manual_s.a.m./s.a.m.pdf

1. Background Setup

Robot PU is an AI-powered humanoid buddy that uses a micro:bit for its brain. While PU is great at moonwalking, he needs a special code library called pxt-billy to speak.

This library uses “Speech Synthesis” to build words out of digital sounds, all without needing an internet connection. It is based on a classic engine called SAM (Software Automatic Mouth).

2. Problem Definition

To make Robot PU talk effectively, we need to solve three challenges:

• The Voice Box: We need to add the speech extension to the MakeCode editor.
• The Script: We need a way to generate random sentences so PU doesn’t sound like a broken record.
• The Performance: We need to make PU’s LED face change while he is talking so it looks natural.

3. Basic Idea of Solutions

1. Extensions: We will use the MakeCode Extension UI to search for and add pxt-billy.
2. Procedural Generation: We will create a Content class that stores lists of words (Subjects, Actions, Objects, and Locations) and picks them at random to form a sentence.
3. Visual Feedback: We will use “blocking” code—commands that run one after another—to open PU’s “mouth” (LEDs) before he speaks and close it after he is finished.

4. Implementation

Step A: Add the Extension

You must teach MakeCode how to speak before the code will work:

1. Open your project at makecode.microbit.org.
2. Click Extensions at the bottom of the toolbox.
3. Paste this URL into the search bar: https://github.com/adamish/pxt-billy.
4. Select the billy extension to add it.

Step B: The Script

Copy and paste this code into your JavaScript tab:

class Content {
    loc: string[];
    act: string[];
    sub: string[];
    obj: string[];

    constructor() {
        this.sub = ["I", "He", "She", "They", "Robot PU"];
        this.act = ["liked", "saw", "heard", "felt", "loves"];
        this.obj = ["me", "you", "the dance", "the song", "the code"];
        this.loc = ["here", "there", "up", "down", "in the lab"];
    }

    private choice(arr: string[]): string {
        return arr[Math.floor(Math.random() * arr.length)];
    }

    cute_words(): string {
        return this.choice(this.sub) + " " +
            this.choice(this.act) + " " +
            this.choice(this.obj) + " " +
            this.choice(this.loc) + ".";
    }
}

let generator = new Content();

// 1. Set global hardware volume (0-255)
music.setVolume(150)

// 2. Set PU's Voice to sound like a high-pitched Elf!
billy.voicePreset(BillyVoicePreset.Elf)

// 3. Make PU talk when a button is pressed
input.onButtonPressed(Button.A, function () {
    let phrase = generator.cute_words();

    // Show a talking face on the LEDs
    basic.showIcon(IconNames.SmallSquare)

    // PU speaks the phrase (This is a blocking command!)
    billy.say(phrase)

    // PU "closes" his mouth
    basic.showIcon(IconNames.Asleep)
})

5. Testing

1. Download the code to your Robot PU.
2. Press Button A: Does PU say a full sentence in a squeaky Elf voice?
3. The Wait: Notice that PU stays on the “Small Square” LED icon until he is completely finished talking. This is because billy.say() is a blocking command.
4. Hardware: If you have a micro:bit V2, the sound comes from his chest. If using V1, check that your speaker is on Pin 0.

6. What Can Be Done Next?

• Custom Vocabulary: Change the words inside the Content class to make PU talk about space, dinosaurs, or school!
• Button B Switch: Add an input.onButtonPressed(Button.B) block that changes the voice to BillyVoicePreset.Dalek for a scary robot effect.
• Chatty Sonar: Use PU’s chest sonar to trigger speech. Make him say “Excuse me!” if someone gets closer than 20cm.

Would you like me to help you add more words to your Content class to make PU’s sentences longer?

To make Robot PU’s sentences longer and more descriptive, we can expand the Content class by adding a descriptor (adjective) and a conjunction (joining word).

Here is the updated script with a more advanced sentence structure.

Advanced Implementation Script

Replace your previous Content class and Button A code with this version:

class Content {
    loc: string[];
    act: string[];
    sub: string[];
    obj: string[];
    adj: string[]; // New: Descriptors
    conj: string[]; // New: Joining words

    constructor() {
        this.sub = ["I", "He", "She", "They", "Robot PU"];
        this.act = ["liked", "saw", "heard", "felt", "loves"];
        this.obj = ["me", "you", "the dance", "the song", "the code"];
        this.loc = ["here", "there", "up", "down", "in the lab"];
        this.adj = ["shiny", "happy", "weird", "fast", "super"];
        this.conj = ["and", "but", "because", "so"];
    }

    private choice(arr: string[]): string {
        return arr[Math.floor(Math.random() * arr.length)];
    }

    /**
     * Creates longer, more complex sentences
     * Structure: [Subject] [Action] [Adjective] [Object] [Conjunction] [Location].
     */
    cute_words(): string {
        return this.choice(this.sub) + " " +
            this.choice(this.act) + " " +
            this.choice(this.adj) + " " +
            this.choice(this.obj) + " " +
            this.choice(this.conj) + " " +
            this.choice(this.loc) + ".";
    }
}

let generator = new Content();
music.setVolume(150);
billy.voicePreset(BillyVoicePreset.Elf);

input.onButtonPressed(Button.A, function () {
    let phrase = generator.cute_words();

    // Animate the face
    basic.showIcon(IconNames.SmallSquare);

    // PU speaks the longer phrase
    billy.say(phrase);

    basic.showIcon(IconNames.Asleep);
})

How it Works?

• Expanded Vocabulary: We added this.adj for adjectives like “shiny” and this.conj for conjunctions like “because.”
• Complex Structure: The cute_words() function now builds a much longer string. Instead of just “I saw the code,” PU might now say: “Robot PU loves the shiny code because there.”
• Memory Usage: Even with more words, the micro:bit can easily handle this because strings are stored efficiently in its memory.

What’s Next?

Since PU can now speak long sentences, would you like me to show you how to add Button B as a “Mood Switcher” that changes his voice from a High-Pitched Elf to a Grumpy Robot?

To add a “Mood Switcher” for Robot PU, we will use Button B to toggle between different vocal personalities. This is done by changing the billy.voicePreset() setting, which alters the speed, pitch, and tone of the speech synthesis engine.

Mood Switcher Implementation

Add this code block to your project. It uses a “variable” to keep track of PU’s current mood so he knows which voice to use when you press Button A.

// 1. Create a variable to track the current mood (0 = Elf, 1 = Robot)
let puMood = 0;

// 2. Button B: The Mood Switcher
input.onButtonPressed(Button.B, function () {
    if (puMood == 0) {
        // Switch to Grumpy Robot mode
        puMood = 1;
        billy.voicePreset(BillyVoicePreset.Robot);
        basic.showIcon(IconNames.Angry); // Visual mood indicator
        billy.say("I am a grumpy robot");
    } else {
        // Switch back to High-Pitched Elf mode
        puMood = 0;
        billy.voicePreset(BillyVoicePreset.Elf);
        basic.showIcon(IconNames.Happy); // Visual mood indicator
        billy.say("I am a happy elf");
    }
    basic.pause(500);
    basic.showIcon(IconNames.Asleep);
});

How it Works

• State Management: The variable puMood acts like a memory. It remembers if PU is currently in “Elf mode” or “Robot mode.”
• Voice Presets: The BillyVoicePreset.Robot setting slows down the speech and lowers the pitch, while BillyVoicePreset.Elf makes it fast and squeaky.
• Visual Cues: We use basic.showIcon to give PU an “Angry” or “Happy” face so you can see his mood change before he even speaks.
• Blocking Speech: Just like our other speech commands, billy.say() will wait for the robot to finish introducing its new mood before the code continues.

Advanced Tip: The “Dalek” Mood

If you want a third mood that sounds like a sci-fi villain, you can add BillyVoicePreset.Dalek to your logic! This preset adds a vibrating, metallic effect to PU’s voice.

Would you like me to show you how to use the V2 Touch Logo on PU’s head to make him “Giggle” when you touch it?

To tweak the voice of the ptx-billy extension for the BBC micro:bit, you primarily adjust two parameters in the config API: Pitch (the frequency of the voice) and Speed (how fast the words are spoken).

The “Billy” extension uses an 8-bit style synthesis. Generally, higher pitches sound younger/feminine, while lower pitches sound older/masculine.

Voice Configuration Guide

According to billy API:

/**
     * Configure voice parameters
     * @param speed how quickly the voice talks. 0 slow, 255 fast.
     * @param pitch how high or low the voice sounds
     * @param throat how relaxed or tense is the tone of voice
     * @param mouth how tight-lipped or overtly enunciating the voice sounds
     */
    //% block Configure Voice
    //% speed.min=1 speed.max=255 speed.defl=72
    //% pitch.min=1 pitch.max=255 pitch.defl=64
    //% throat.min=1 throat.max=255 throat.defl=128
    //% mouth.min=1 mouth.max=255 mouth.defl=128
    //% group="micro:bit (V2)"
    //% weight=8
    export function configureVoice(speed: number, pitch: number, throat: number, mouth: number): void {
....
}

Age Group	Target Voice	Pitch	Speed	Why these settings?
Toddler	High-pitched/Squeaky	200–255	80	Max pitch creates a tiny, cartoonish feel; slower speed mimics early speech.
10yo Boy	Pre-pubescent	160	100	High pitch, but lower than a toddler. Standard speed for clarity.
10yo Girl	Bright/Light	180	110	Slightly higher pitch and faster tempo than a boy of the same age.
Teenager	Fast/Energetic	140	150	Mid-range pitch but very high speed to mimic fast-talking teens.
Young Adult	Clear/Balanced	100–120	110	Standard “default” settings; clear and modern-sounding.
Middle Age	Deep/Settled	80	95	Lower pitch creates a more “authoritative” or mature tone.
Old Person	Raspy/Slow	60	70	Very low pitch and slow speed creates the effect of a weathered voice.

How to apply this in MakeCode

In the JavaScript/Python editor, your configuration block would look like this (using the “Middle Age” example):

// Middle Age Voice Example
billy.configure(80, 95, 128, 0)
billy.say("Hello, how are you today?")

Note: The configure function usually takes four arguments: (speed, pitch, throat, mouth). While Pitch and Speed are the most impactful, you can slightly increase the Throat value (the 4th parameter) to 140+ for older voices to make them sound “grittier.”

To improve the performance of wall detection, move walk command right after the sonar distance reading, then, reduce the talking by adding pause.

Talking Longer

Following is an example in which robot PU made a joke.