GoKawiilKoppar releases open-source USB-C LTE modem board design on GitHub
A hobbyist project called Koppar has published the full design for a USB-C LTE modem that exposes itself to a computer as a network adapter, serial AT-command ports and a USB sound card, enabling LTE data, SMS and voice calls with audio routed over USB. The repository includes the KiCad schematic and board files, JLCPCB manufacturing and assembly files, a design review document, and RP2040 firmware, letting anyone fabricate and assemble the board themselves.
GoKawiil's interpretation of the reporting above, not reported fact.
By releasing gerbers, BOM and placement files rather than a finished product, the creator lowers the barrier for developers to give any computer or script its own phone line, which could appeal to makers building automated call-handling or AI voice agents. The accompanying review document, which notes what was checked against datasheets and what remains open, suggests the design is still maturing rather than a finished commercial product.
- Open-source board turns a nano-SIM into LTE data, SMS and voice access over a single USB-C port.
- Computer sees the module as three standard USB devices: network adapter, serial AT-command port, and sound card.
- Full fabrication and assembly files for JLCPCB are published, allowing anyone to build their own unit.
Quectel EC25-EUX LTE Module — This is the exact cellular module featured in the Koppar board, giving developers and makers direct access to LTE data, SMS, and voice over AT commands. It's a great way to experiment with embedded connectivity projects, prototype your own phone-line-on-USB device, or just understand the hardware behind the article.
See Quectel EC25-EUX LTE Module on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: github.com, 2026-10-31
Published there as: “Show HN: A USB-C LTE modem that gives my computer a phone line”
Read the original report → The summary and analysis above are GoKawiil's own, written from reporting by the source above. Facts and quotes belong to the original publisher.