The archive · Product Ideas · Product decision · 2024
Murex Robotics shrinks a five-port Ethernet switch to 45×42 mm, then open-sources it
A robotics team designs its own five-port Ethernet switch for its ROV, squeezing it to 44.9×42.2 mm with a ~$7 board cost, and publishes the files.
Murex Robotics
What it had to solve
Murex Robotics needed several Ethernet links inside its underwater robot, but every commercial switch was built for racks and retail — enclosed, bulky, feature-heavy and priced for volume buyers. With the robot's links running far below gigabit speeds, size and cost mattered more than speed.
How it works
Murex Robotics' underwater robot needed several Ethernet links, but every switch the team could buy was a retail product: enclosed, full of management features, and priced for volume buyers. Its own constraint set was different — the tether capped link speed far below gigabit, so five 100BASE-TX ports were plenty, as long as the board was small and cheap enough to embed.
So the team designed one. The mrxSwitch pairs the IP175Gx switch IC with magnetics soldered directly onto a four-layer board, which let full-size Ethernet jacks become 1.25mm-pitch Picoblade connectors and the whole board shrink to 44.9 by 42.2 mm. V2 removed the config components and EEPROM, cut board area by 30% and the bill of materials by 15%, and released the complete KiCad design openly on GitHub; a first run of about 25 boards came to roughly $7 each.
Posted to Hacker News as the world's smallest and cheapest networking switch, the project drew 666 points and 158 comments. Robotics and embedded engineers asked to buy boards and download the layout files, and when commenters challenged 'cheapest', the team answered with the ~$7 board cost and explained the design decisions came from its underwater robot. The documentation page, last updated in June 2025, still lists V2 as tested and functional.
Why it lands
- The spec came from the machine: because the robot's links ran below gigabit, the team could trade speed for the two things it actually needed — size and cost.
- Putting the magnetics on the board removed the biggest size driver, the full-size Ethernet jack, letting the ports shrink to 1.25mm pitch.
- Every feature that was not essential was deleted — management, config EEPROM, enclosure — so cheapness came from the design, not from volume buying.
- Releasing the KiCad files turned a bespoke board into a reference design any robotics or embedded team could copy or improve.
What it did
The Show HN post drew 666 points and 158 comments on 16 June 2024: embedded and robotics engineers asked for boards and files, pushed back on the 'cheapest' claim, and the team answered with real numbers. V2 was already tested and functional, and the documentation stayed live and updated into mid-2025.
What you can take
Spec against your own machine, not the market's biggest buyer: choose the speed you need, strip what you don't, and the missing part shrinks to buildable size — then publish it so the niche copies it.
Since then
The board stayed open after its Hacker News debut: the electrical-2024 GitHub repository carried the V2 layout files, a blog post documented V1, and the docs page remained live with a changelog through June 2025. Commenters' suggestions — VLAN management, an even smaller form factor, a $7 cost target — were acknowledged by the team for future revisions, and the team said the switch was already in service inside its underwater robot.
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