A microcontroller-based stylophone with recording and playback capabilities, built around the Raspberry Pi Pico. This project reimagines the classic analog instrument with modern digital features, including an OLED display and non-volatile memory for storing recorded tracks.
- Sound Generation: Produces a square wave tone with a classic synthesizer sound.
- Multiple Octaves: Three selectable octaves (low, middle, high).
- Volume Control: Adjustable volume with 8 levels.
- Recording & Playback: Record, save, and play back musical sequences.
- Persistent Memory: Saves the recorded track and user settings (volume, octave) to a
settings.jsonfile on the device. - OLED Display Interface: A 128x64 SSD1306 OLED screen provides a menu-based interface for all functions.
- Tactile Controls: 5-button navigation for intuitive menu control.
- Portable Design: Powered by a 9V battery for on-the-go use.
- Raspberry Pi Pico Core: Utilizes a Raspberry Pi Pico for all processing and hardware control.
| Component | Quantity |
|---|---|
| Raspberry Pi Pico | 1 |
| 5mm LED | 2 |
| 10Ω Resistor (1/4W) | 1 |
| 1kΩ Resistor (1/4W) | 21 |
| 10kΩ Resistor (1/4W) | 1 |
| 10uF Capacitor | 1 |
| 0.96" OLED Display | 1 |
| LM2596 Step-down Converter | 1 |
| 6x6mm Tactile Switch | 5 |
| Female Pin Headers | 5 |
| Latching Switch | 1 |
| 9V Battery | 1 |
| 1W 8Ohm Speaker | 1 |
A 3D-printed enclosure can also be made for the device. A model of the enclosure has been prepared for this purpose, and it is available as the housing.stl file.
The device is controlled by a MicroPython script (main.py) running on the Raspberry Pi Pico.
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Sound Generation: The stylus's position on the resistive keyboard is read as an analog value by the Pico's ADC (Analog-to-Digital Converter). This value is then mapped to a specific musical note frequency. The sound is generated using PWM (Pulse Width Modulation) sent to a 1W speaker.
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UI & Menu: A menu-driven interface is displayed on the 128x64 OLED screen. The user navigates the menu using a 5-button keypad. The available options are Volume, Tone (Octave), Record, and Play.
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Recording & Playback: The recording function captures a sequence of notes and their timings. It records pairs of
(frequency, timestamp)to a list. The playback function iterates through the recorded list, playing back the notes with the correct timing. -
Persistence: The recorded song, as well as the volume and tone settings, are saved to a
settings.jsonfile in the Pico's flash memory. This allows the device to retain settings and recordings between power cycles.
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Install MicroPython: If you haven't already, install MicroPython on your Raspberry Pi Pico. You can find the official instructions here.
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Install
ssd1306.py: The OLED display requires thessd1306.pylibrary. You can find it here and save it to your Pico. -
Upload the Software: Copy the
main.pyfile to your Raspberry Pi Pico. The easiest way to do this is by using an IDE like Thonny, which has a simple interface for managing files on a MicroPython device.
| Control | Function |
|---|---|
| Up/Down Buttons | Navigate through the main menu. |
| Left/Right Buttons | Decrease/increase the volume or tone (octave). |
| OK Button | Select a menu option; start/stop recording or playback. |
| Stylus | Play notes by touching the corresponding keys. |
- Power On: Connect a 9V battery and flip the power switch. The green LED will light up, and the main menu will appear on the OLED display.
- Play Music: Simply touch the stylus to any of the metal keys to play a note.
- Navigate Menu: Use the Up and Down buttons to highlight a menu option.
- Select Option: Press the OK button to enter the selected menu (Volume, Tone, Record, or Play).
- Adjust Volume/Tone: In the Volume or Tone menus, use the Left and Right buttons to make adjustments. Press Up or Down to exit and save.
- Record: Select "RECORD" from the main menu and press OK. Press OK again to start recording. The red LED will blink. Play your tune, and press OK to stop. The recording will be saved automatically.
- Playback: Select "PLAY" from the main menu and press OK. Press OK again to start playback of the last recorded track. The red LED will stay lit during playback.
| Symptom | Possible Cause | Suggested Solution |
|---|---|---|
| Screen works, but the green power LED is off. | The green LED is burnt out. | Replace the green LED. |
| The green power LED is on, but the screen is blank. | The OLED display is damaged or disconnected. | Check the display's connections. If the problem persists, replace the display module. |
| Nothing works (no screen, no LEDs). | The 9V battery is dead. | Replace the 9V battery. |
| The screen and LEDs work, but there is no sound. | The speaker is damaged or disconnected. | Check the speaker wiring. If the problem persists, replace the speaker. |
- Enhanced Sound Engine:
- Add a vibrato effect using a Low-Frequency Oscillator (LFO).
- Connectivity:
- Add MIDI output via USB, allowing the stylophone to function as a MIDI controller.
- Code Refinements:
- Refactor the code for better efficiency, especially the recording and display update logic.
This project is licensed under the MIT License. See the LICENSE file for details.