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Frozen

tsmiltonAgents·20260721_countdown·hw/countdown/frozen.kicad_pcb

Frozen PCB layout, top view — open source STM32 board by tsmiltonAgents

About the Frozen PCB

Frozen is an open source STM32 PCB design by tsmiltonAgents, published on GitHub. It is a 4-layer board measuring 46 × 23 mm, with 22 components from 11 distinct parts.

Its main chip is the STM32L031G6U6, from the STM32 family. By type, the board carries 9 resistors, 8 capacitors, 1 IC, 1 crystal, 1 battery holder and 1 switch.

From the project

A 46 × 23 mm, 4-layer keyring PCB that counts down the hours to 10 October 2026, midday on a red 4-digit 7-segment display. Powered by a CR2032, it keeps time for years in deep sleep; press the button and the hours remaining glow for 8 seconds. Under 100 hours to go it switches t

A 46 × 23 mm, 4-layer keyring PCB that counts down the hours to 10 October 2026, midday on a red 4-digit 7-segment display. Powered by a CR2032, it keeps time for years in deep sleep; press the button and the hours remaining glow for 8 seconds. Under 100 hours to go it switches to minutes (decimal point lit as the marker). At T-0 it shows 0.0.0.0.

- STM32L031G6U6 (QFN28) runs the show: RTC on a 32.768 kHz crystal, Stop-mode sleep at ~1 µA with full RAM retention. - XINGLIGHT XL-SA2401SRWC 0.2" 4-digit red display, common cathode, multiplexed directly from GPIO (segments through 330 Ω on…

Frozen, from the project README
From the project README

Main components on the Frozen

STM32L031G6U6

Frozen bill of materials (BOM)

22 components, 11 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
STM32L031G6U6
U1
1
32.768KHZ
32.768kHz
Y1
1
BS-08-B2AA001
BT1
1
XL-SA2401SRWC
DS1
1
TS-1187A-B-A-B
SW1
3
100NF
100nF
C1, C2, C3
1
1UF
1uF
C4
2
10UF
10uF
C5, C6
2
15PF
15pF
C7, C8
8
330R
R1, R2, R3, R4, R5, R6, R7, R8
1
10K
10k
R9

Frozen design files

The KiCad project lives in the tsmiltonAgents/20260721_countdown repository on GitHub; these links point at the commit this page was built from.

Frozen: common questions

What microcontroller does the Frozen use?

The Frozen is built around the STM32L031G6U6, from the STM32 family.

How big is the Frozen PCB?

The Frozen measures 46 × 23 mm, has 4 copper layers and is 1.6 mm thick.

How many components are on the Frozen?

22 components, from 11 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 Frozen design files?

From the tsmiltonAgents/20260721_countdown repository on GitHub, which has the KiCad layout and the BOM; the links under Design files point to each one.

Can I use the Frozen design in my own project?

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

Can I test firmware for the Frozen 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.

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