Supported decoder

OpenStint Decoder

Open-source SDR lap timing — built by the same hands as LapBeeps.

💚 Open source 📡 SDR-based decoder 💰 Complete setup under $100

What it is

Professional-grade timing, off the shelf.

OpenStint is a software-defined-radio (SDR) lap timing decoder. Instead of a sealed proprietary box, it turns a cheap SDR dongle and a loop antenna into a precise RC timing system — and does all the clever signal work in open-source software.

It reads the open OpenStint transponder protocol and the RC3 / RC4 / MRT transponders most clubs already own, so you don't have to throw out your gear to try it.

And it's a bit personal: both LapBeeps and OpenStint are built by me. OpenStint came first — this is the decoder LapBeeps was designed around from day one. If anything ever doesn't line up, there's one inbox to email, not a support maze.

An OpenStint SDR decoder and antenna set up trackside — The whole decoder, trackside: an SDR dongle and a loop antenna. A Raspberry Pi as host computer. That's it.

What you need

A complete setup for under $100.

No five-figure timing system, no annual licence. Here's the entire shopping list.

≈ $40

An SDR dongle

An RTL-SDR v4 (~$40) is all you need. Prefer more headroom? A HackRF One clone runs about the same, the original around $120.

a few $

A loop & antenna

A wire loop under the track and a short antenna. Add the open-source OpenStint pre-amp when you want a wider, cleaner detection window.

≈ $5 each

Transponders

Order the open transponder boards from JLCPCB for a few dollars apiece — or keep using the RC3 / RC4 / MRT transponders you already own.

A computer you own

The decoder sips resources — a spare laptop or a Raspberry Pi 3B+ is plenty. LapBeeps runs right alongside it.

Already have a laptop and a few RC3/RC4 transponders? You're looking at the price of one SDR dongle to get on the air.

How it works

From the loop to the leaderboard.

Transponders broadcast

Each car carries a transponder sending its unique ID — the OpenStint protocol, or the RC3 / RC4 / MRT signals you already race with.

The SDR listens

An off-the-shelf SDR dongle and a loop antenna pick up every crossing. Adaptive filters clean up the signal in software, not in expensive hardware.

OpenStint decodes

Passing times are pinned to the signal-strength peak — not a rough threshold — and the decoder publishes each crossing over the network.

LapBeeps scores

LapBeeps listens, scores, ranks, and announces — live. No bridge, no plugin, no extra configuration. It just works.

OpenStint + LapBeeps

Made for each other.

✓ Native support in LapBeeps — plug it in and race, no setup
✓ Same author builds both LapBeeps and the OpenStint decoder
✓ Open protocol — community supported and free to extend
✓ Reuses your existing RC3 / RC4 / MRT transponders
✓ Precise, signal-strength-based passing detection
✓ Runs happily on a Raspberry Pi 3B+ for a permanent install

Open source

It's all out in the open.

zsellera/openstint

The SDR laptiming decoder. Runs on a laptop, a Raspberry Pi, or anything Linux/Windows.

View repo

zsellera/openstint-transponder

Reference transponder design. Order the boards straight from JLCPCB and build a fleet on the cheap.

View repo

zsellera/openstint-preamp

Optional loop amplifier for a cleaner signal and a bigger detection window across the track.

View repo