Plantone: ESP32 Plant-to-Music Synthesizer
Plants generate small, constantly shifting electrical signals across their leaves. Plantone reads those signals and turns them into sound in real time: an instrument played by a living plant instead of a musician. We built the device from a bare-breadboard signal test through a pre-production unit with its own enclosure and controls.
The Challenge
The core problem sat at the boundary between biology and electronics: plant signals are tiny, noisy, and slow compared to audio frequencies. Turning that raw input into music that sounds intentional, not random, meant building a full signal chain (amplification, filtering, a synthesis engine) and fitting all of it onto hardware small enough to sell as a consumer product.
Every choice fed into the next one. A cleaner analog front end simplified the DSP work downstream. A more capable chip freed up options for reverb and multi-channel panning but changed the power and cost budget. We also had to make it playable: octave selection, sensitivity, and reverb needed physical controls a person could operate without a manual.
What We Built
- Signal chain to capture plant electrical activity and convert it into an audio-rate stream
- Hardware synthesizer running on a dedicated DSP chip, later ported to ESP32
- USB MIDI output, prototyped first on an ATtiny85
- Octave selection, sensitivity slider, reverb, and channel panning controls
- Noise reduction across the analog and digital stages (residual headphone noise stayed on hold)
- Onboard display and a save function for stored settings
- Web interface for adjusting common settings without the physical controls
- Encoder knob added for on-device settings navigation
- USB-C connector to replace the original micro-USB (still open)
- Enclosure design and internal layout for the first sellable unit
- Sample assembly on a factory-produced PCB (still open as of 2024-12)
Delivery
The project moved from a breadboard proving the signal-to-audio concept, through a prototype that generated real music from a live plant, to a pre-production device with its own board and enclosure. Late-stage work focused on the details that separate a working prototype from a shippable product: connector standardization, panel layout, and a settings interface usable without a computer. The factory-PCB sample and the USB-C swap remained open. This is our own R&D product; we report no sales figures.
Engineering at a glance
- Scale. About 611 engineering hours, 2 engineers, 2021-08 to 2024-12.
- Prototype in the first week. The bill of materials and a breadboard prototype came on 2021-08-11 and 08-12, and the ESP32 port took about 7 engineering hours on 08-18. USB MIDI on an ATtiny85 followed in late August (about 23 hours).
- Signal chain. Plant electrode input analysed and converted to an audio-rate stream (about 16 engineering hours), then a hardware synthesizer on a dedicated DSP chip (about 95 hours).
- Prototype rework. The largest single block, about 230 engineering hours: thin flexible electrode wires, a random instrument mode when the electrode signal appears or disappears, battery charging, and a power switch.
- Controls and interface. Octave selection, an inverted sensitivity slider from 5 to 100 percent, reverb, channel panning, scales, an I2C display, an encoder for common settings, and a web UI with saved patterns that applies changes as the slider moves.
- PCB and enclosure. Rear connectors moved onto the board (about 37 engineering hours), the board fitted into an enclosure with side connectors and a display cutout, and a troubleshooting pass on loose solder joints (about 28 hours).
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