Tinyradio

Tiny radio keychain!!

A keychain that is also a working fm radio:D

Specifications

• XIAO RP2040 microcontroller - edit firmware without any extra equipment
• RDA5807M - cheap and widely available FM radio chip
• Wired earphones act as an antenna for the radio
• Runs on a CR3032 coin cell battery
• 58 x 42.4mm (can be made even smaller if you don't want mounting holes)
• bom can be found as bom.csv

Usage

• Provide a battery and wired earphones.
• To flash the firmware, follow these instructions.
• Press the left knob down to turn on/off.
• Turn the left knob to adjust volume.
• Turn the right knob to adjust frequency.
• Adjust the earphone wire position and length to adjust reception of signals.

Why

I made it because I like tiny things (my most prized pencilcase posession is a tiny calculator), I like keychains, and I like radios. I'm also new to hardware stuff so it was nice to get started with a simpler receiver. That, and I had impulse-bought RDA5807 chips a year or so ago. I also wanted a neat trinket I could give to radio people when I meet them at conventions and stuff. Additionally, my current radio is rather large... so I can't really carry it around anywhere.

Process

The development process is logged in detail here and later here. It took me quite a while (~1 1/2 month of consistent work) because I was pretty much new to PCB design. I learned a lot about KiCad and the design process through this project.

Next steps

I want to try making multiple at a time (larger scale) so that I have enough to go around. Also, harder projects (tiny calculator...).

Zine