FalCAN Probe Is an Open-Source, STM32-Based USB to CAN/RS-485/RS-422 Adapter

Key Takeaways

• FalCAN Probe supports CAN, RS‑485, and RS‑422 via USB‑C
• Firmware uses candleLight_fw fork, compatible with Linux gs_usb driver
• Device switches modes with jumper JP4, no custom drivers needed
• Open‑source hardware files hosted on GitHub under CC BY‑SA 4.0
• Priced at 249 DKK (~$36), includes VAT for EU buyers

Pulse Analysis

The embedded systems market has seen a surge in open‑source hardware that lowers entry barriers for prototype development. Traditional USB‑to‑bus adapters such as CANTact Pro or MeatPi’s Ollie focus on a single protocol, forcing engineers to stock multiple tools. The FalCAN Probe disrupts this model by delivering a compact, USB‑C‑based solution that simultaneously handles CAN, RS‑485, and RS‑422, addressing the growing demand for versatile test equipment in automotive, industrial automation, and IoT applications.

At the heart of the FalCAN Probe is an STM32F042 Cortex‑M0 microcontroller running a fork of the candleLight_fw firmware. This firmware leverages the Linux kernel’s gs_usb driver, meaning the device appears as a standard CAN interface on Ubuntu, Raspberry Pi OS, or other distributions without installing proprietary drivers. Mode selection is achieved via a simple JP4 jumper: open for CAN (gs_usb) and closed for a CDC serial port linked to USART1 for RS‑485/RS‑422. The board also exposes SWD pins and GPIO headers, turning it into a low‑cost development platform for custom firmware or even an ST‑Link‑style programmer.

Pricing the FalCAN Probe at roughly $36 USD makes it one of the most affordable multi‑protocol adapters on the market, especially when compared to isolated industrial tools that can exceed $200. Its fully open‑source design—schematics, PCB layout, and bill of materials on GitHub—encourages community contributions and rapid iteration. For startups and hobbyists alike, the device offers a scalable way to generate bus traffic, perform protocol analysis, or prototype custom communication stacks, ultimately accelerating product development cycles and reducing tooling overhead.