OpenFC

An open-source VEX V5 field controller. One small board drives all four competition ports, so you can run real autonomous and driver periods at practice instead of shouting a countdown across the room.

Plug it in over USB and drive it straight from this page — nothing to install, no app, no account. Everything runs in your browser.

Run a Practice Match ▶Flash FirmwareDocumentation

Four ports, driven together

Drives the ENABLE/DISABLE and DRIVER/AUT lines of four V5 Competition Switch ports in unison, optically isolated from the V5.

The board owns the clock

Once a period starts, the countdown runs on the board. Close the laptop lid or unplug the cable and the match still finishes on time.

Fails to disabled

It boots disabled, and outside a timed period it disables itself within 600 ms of losing contact with the host. Robots stop when things go wrong.

How it works

  1. 1Flash the board

    Connect over USB and install the certified firmware in one click. The page hashes what is actually running and tells you whether it matches an official release.

  2. 2Set your periods

    Autonomous, driver, or a full match. Move between periods yourself or on a timed gap. Durations are yours to pick — 15/90 by default, anything up to 10 minutes.

  3. 3Run the match

    A full-screen countdown drives the field. Enter advances the period, space stops everything at once.

Build it yourself

The hardware, the firmware and this site are open source. An ESP32-S3, four optocouplers and four RJ11 jacks — the schematic and the build are public.

Hardware reference →

Drive it from your own code

The board speaks newline-delimited JSON over USB serial at 115200 baud. Any language that can open a serial port can start a period or trip an e-stop.

Protocol reference →

Keep the field clear. OpenFC enables and disables real robots. Keep hands clear whenever the field is enabled, and confirm the board behaves as expected in your setup before relying on it.

Requires Chrome, Edge, or Opera — the Web Serial API.