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1. TTS with Espeak and Pico2Wave

In this lesson, we’ll use two built-in text-to-speech (TTS) engines on Raspberry Pi — Espeak and Pico2Wave — to make the Fusion HAT+ talk.

These two engines are both simple and run offline, but they sound quite different:

• Espeak: very lightweight and fast, but the voice is robotic. You can adjust speed, pitch, and volume.

• Pico2Wave: produces a smoother and more natural voice than Espeak, but has fewer options to configure.

You’ll hear the difference in voice quality and features.

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1. Testing Espeak

Espeak is a lightweight TTS engine included in Raspberry Pi OS. Its voice sounds robotic, but it is highly configurable: you can adjust volume, pitch, speed, and more.

Run the program

cd ~/ai-lab-kit/llm
sudo python3 tts_espeak.py

• You should hear the Fusion HAT+ say: “Hello! I’m Espeak TTS.”

• Try changing the tuning parameters in the code to experiment with how amp, speed, gap, and pitch affect the sound.

Code

from fusion_hat.tts import Espeak

# Create Espeak TTS instance
tts = Espeak()
# Set amplitude 0-200, default 100
tts.set_amp(200)
# Set speed 80-260, default 150
tts.set_speed(150)
# Set gap 0-200, default 1
tts.set_gap(1)
# Set pitch 0-99, default 80
tts.set_pitch(80)

tts.say("Hello! I’m Espeak TTS.")

Code explanation:

• tts.set_amp() — Controls the volume (0–200).

• tts.set_speed() — Adjusts the speaking speed (80–260).

• tts.set_gap() — Sets the word gap (0–200).

• tts.set_pitch() — Sets the pitch (0–99).

• tts.say() — Converts text to speech and plays it.

💡 Tip: Try increasing the pitch and speed to make the robot sound cheerful, or lowering them to make it sound serious.

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2. Testing Pico2Wave

Pico2Wave produces a more natural and human-like voice compared to Espeak. It’s very easy to use, but less flexible — you can only change the language, not the pitch, speed, or volume. This makes Pico2Wave a great choice when you want clear and smooth speech without too much configuration.

Run the program

cd ~/ai-lab-kit/llm
sudo python3 tts_pico2wave.py

• You should hear the Fusion HAT+ say: “Hello! I’m Pico2Wave TTS.”

• Try changing the language (for example, es-ES for Spanish) and listen to how the voice changes.

Code

from fusion_hat.tts import Pico2Wave

# Create Pico2Wave TTS instance
tts = Pico2Wave()

# Set the language
tts.set_lang('en-US')  # en-US, en-GB, de-DE, es-ES, fr-FR, it-IT

# Quick hello (sanity check)
tts.say("Hello! I'm Pico2Wave TTS.")

Code explanation:

• tts.set_lang() — Sets the output language for speech synthesis.

  • en-US (default)

  • en-GB

  • de-DE

  • es-ES

  • fr-FR

  • it-IT

• tts.say() — Converts the text to speech and plays it immediately.

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Troubleshooting

• No sound when running Espeak or Pico2Wave

  • Check that your speakers/headphones are connected and volume is not muted.

  • Run a quick test in terminal:

    espeak "Hello world"
    pico2wave -w test.wav "Hello world" && aplay test.wav
    

  If you hear nothing, the issue is with audio output, not your Python code.

• Espeak voice sounds too fast or too robotic

  • Try adjusting the parameters in your code:

    tts.set_speed(120)   # slower
    tts.set_pitch(60)    # different pitch
    

• Permission denied when running code

  • Try running with sudo:

    sudo python3 test_tts_espeak.py
    

Comparison: Espeak vs Pico2Wave

Feature	Espeak	Pico2Wave
Voice quality	Robotic, synthetic	More natural, human-like
Languages	Default English	Fewer, but common ones
Adjustable	Yes (speed, pitch, etc.)	No (only language)
Performance	Very fast, lightweight	Slightly slower, heavier