● Covered by 1 source · 1 reportLow impact1 neutral
Open-Source USB-C LTE Modem Provides Data, SMS, and Voice Calls to Computers
Key points
- 4-layer board provides LTE data, SMS, and voice calls.
- Connects via a single USB-C cable, using a nano-SIM.
- Computer sees it as three standard USB devices.
- Designed with open-source KiCad files and JLCPCB assembly instructions.
- Features RP2040 microcontroller for control and firmware updates.
New USB-C LTE Modem Functionality
A new open-source hardware project introduces a USB-C LTE modem designed to give computers direct access to cellular networks. This 4-layer board supports LTE data, SMS messaging, and voice calls. Users insert a nano-SIM card and connect the device to a computer via a single USB-C cable. The computer then recognizes three standard USB devices, allowing for immediate use of cellular functions.
Hardware Design and Components
The modem board is powered by 5V from the USB-C connection and includes power regulation for its components, such as a 3.8V/3A buck converter for the LTE module's transmit bursts and 3.3V for the USB hub and RP2040 microcontroller. It features three LEDs to indicate network status (NET), incoming calls (RING), and active calls (CALL). The design omits a battery, screen, or speaker, relying on the host computer for audio output.
The board was designed using KiCad 10, with all project files, including footprints, symbols, and 3D models, provided. Manufacturing instructions are available for JLCPCB, including Gerber files, Bill of Materials (BOM), and Component Placement List (CPL) for assembly.
Firmware and Debugging
The device utilizes an RP2040 microcontroller, which controls the LTE module's power and reset lines. The RP2040 boots into its USB bootloader when blank, allowing for easy firmware updates via a .uf2 file. For debugging and recovery, the board includes pads for BOOT+GND to enter USB bootloader mode, SWD for debugging with probes like Pico Debug Probe, and USB_BOOT+1V8 for emergency modem updates.
Impact and Use Cases
This open-source modem provides a direct way for computers to integrate cellular capabilities, enabling scenarios such as answering calls through a headset, routing calls to scripts, or connecting to AI agents for automated interactions. Its open design allows for customization and integration into various projects requiring direct cellular connectivity without relying on smartphones or dedicated cellular gateways.
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Primary sources
GitHub cmc_internal/api GitHub github/collect GitHub Koppar-AI/koppar-lte-modem GitHub _private/browser GitHub get-started/accessibility GitHub en/copilotReporting from
A new open-source USB-C LTE modem board has been developed, allowing computers to access LTE data, send SMS, and make voice calls via a single USB-C connection. This device integrates a nano-SIM slot and presents itself as three standard USB devices, enabling computers to handle calls through a headset or automate interactions with scripts or AI agents.