HardLabs

Firefly2

candykingdom·firefly2·hardware/puck/firefly2.kicad_pcb

Firefly2 PCB layout, top view — open source STM32 board by candykingdom

About the Firefly2 PCB

Firefly2 is an open source STM32 PCB design by candykingdom, published on GitHub. It is a 2-layer board measuring 41.4 × 41.3 mm, with 21 components from 18 distinct parts.

Its main chip is the STM32G070KBTX, from the STM32 family. Other key parts include the RFM69HCW, CH340X, XL-0807RGBC-WS2812B and AP2112K-3.3. By type, the board carries 5 ICs, 4 diodes, 4 capacitors, 3 connectors and 3 resistors.

It belongs with the rf & radio designs in this gallery.

From the project

Small blinkenlight boards that sync up using radios

Wireless LED control for Burning Man art installations, bikes, and wearables. Devices driving WS2812 strips self-organize over 915 MHz RFM69 radios into a flood mesh with exactly one master, share a network clock via heartbeats, and render effects as pure functions of network time — so every device animates in sync without streaming frames.

New to the project? Start with GETTING_STARTED.md. Working in the code (human or agent)? The mental model lives in docs/index.md and the shared Claude Code/Codex ground rules in CLAUDE.md.

Main components on the Firefly2

STM32G070KBTXRFM69HCWCH340XXL-0807RGBC-WS2812BAP2112K-3.3

Firefly2 bill of materials (BOM)

21 components, 18 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
STM32G070KBTX
SAMD21E18
U1
1
RFM69HCW
RFM69CW
U2
1
CH340X
MIC5504
U3
1
XL-0807RGBC-WS2812B
74LVC1G125
U4
1
AP2112K-3.3
MOSFET
U5
1
614105150721
J2
1
CONN_01X01
J3
1
CONN_01X04
P3
2
hole
H1, H2
2
ESD5Z5.0
WS2812B
D1, D4
1
C2286
WS2812B
D2
1
SRV05-4-P-T7
WS2812B
D3
1
100NF
10uF
C1
2
100NF
1uF
C2, C3
1
100NF
DNP
C4
1
4K7
470
R1
1
10k
R2
1
22K
20
R3

Firefly2 design files

The KiCad project lives in the candykingdom/firefly2 repository on GitHub; these links point at the commit this page was built from.

Firefly2: common questions

What microcontroller does the Firefly2 use?

The Firefly2 is built around the STM32G070KBTX, from the STM32 family.

How big is the Firefly2 PCB?

The Firefly2 measures 41.4 × 41.3 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the Firefly2?

21 components, from 18 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.

Where can I download the Firefly2 design files?

From the candykingdom/firefly2 repository on GitHub, which has the KiCad layout and the BOM; the links under Design files point to each one.

Can I use the Firefly2 design in my own project?

The repository has no license, so all rights stay with candykingdom. Use it as a reference, and ask the author before reusing the design.

Can I test firmware for the Firefly2 without the hardware?

Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug STM32 firmware against it before you order a PCB.

More boards in firefly2

Similar boards