As electronic devices become increasingly compact, integrating full functionality into ultra-small form factors remains a major challenge. While a miniature watch-style FM radio was previously achieved, further miniaturisation—down to an earbud-sized device—introduces design complexity, space constraints, and control limitations that make a fully featured solution difficult to present in a single implementation.
This project introduces a simplified earbud-size FM radio, designed to fit entirely inside an AirPods-style enclosure. Instead of offering full tuning control, the system operates as a fixed-frequency FM radio, preconfigured using an external microcontroller. Once programmed, the FM chip works independently, allowing users to listen to a preset FM station or repurpose the device as a long-range FM spy receiver tuned to a matching transmitter frequency.
Key Features
- Ultra-compact FM radio design that fits inside an earbud
- Uses the RDA5807M FM stereo radio module
- Fixed, pre-programmed FM frequency
- External programming via IndusBoard Coin / Arduino over I²C
- Minimal component count for extreme miniaturisation
- Two exposed contact pads for reprogramming frequency when needed
- Powered by a small TWS earbud Li-Po battery (30–50mAh)
- Direct audio output to a 7mm, 16-ohm earbud speaker
- Optional FM transmitter support for spy or monitoring applications
Applications
- Experimental ultra-miniature FM radio designs
- Wearable and embedded electronics projects
- Proof-of-concept for earbud-scale RF devices
- FM-based audio monitoring or spy applications
- Learning platform for RF modules and compact PCB design
- Foundation for future MCU-controlled micro radio systems
This earbud-size FM radio demonstrates how functional RF electronics can be pushed into extremely small form factors by simplifying control and design. While limited to a preset frequency in its current form, the project lays the groundwork for a fully programmable, ultra-compact FM radio. Future iterations with tiny SMD microcontrollers promise to unlock complete control—bringing true standalone FM functionality to earbud-scale devices.