Most USB-to-bus adapters, including tools like CANTact Pro or MeatPi’s Ollie V1 and V2, typically support either CAN or RS-485/RS-422 as fixed-function serial devices. In contrast, the FalCAN Probe by Anders B. Nielsen is a multi-protocol USB adapter based on the STM32F042 microcontroller.
The FalCAN Probe is a compact open-source USB Type-C board that connects a computer to CAN, RS-485, and full-duplex RS-422 networks. Instead of using a fixed USB bridge, it exposes the MCU’s native USB interface along with SWD and GPIOs, and can also be used as a small Arm Cortex-M0 development platform.
FalCAN Probe specifications:
- MCU – STMicro STM32F042C6Tx Arm Cortex-M0 microcontroller @ 48 MHz with 32KB flash, 6KB SRAM
- Host Interface – USB 2.0 Full Speed via USB Type-C port
- Interfaces (non-isolated)
- CAN bus via Texas Instruments SN65HVD230 transceiver; enumerates as a GS_USB CAN device when jumper JP4 is open
- RS485 and full-duplex RS422 via dual SP3485EN transceivers
- Expansion
- 2x 17-pin GPIO expansion headers
- Unpopulated female DE-9 (DSUB-9) footprint for CAN standard pinout
- Exposed USART1 (PB6/PB7) for external USB-to-UART usage
- Header pins for GPIOs, boot configuration, SWD debugging, and bus routing (JP3/JP4)
- Debug – Dedicated header for SWD programming
- Misc – Green and Red status LEDs
- Power – 5V via USB-C, regulated by an on-board MIC5504-3.3 LDO
- Dimensions – TBD (4-layer FR4 PCB ~1.6mm thickness)
What makes the FalCAN Probe different from similar tools like CANable or Candlelight adapters is its firmware. It uses a fork of the candleLight_fw that supports the mainline Linux gs_usb kernel module, meaning you can plug it into an Ubuntu or Raspberry Pi OS and use standard can-utils without installing any custom drivers. Note: The FalCAN Probe firmware further adds support for RS-485 and RS-422 mode switching on top of the standard CAN capabilities, and the hardware itself exposes the STM32 development pins.
Mode switching is handled using simple hardware jumpers checked at startup. If JP4 is left open during reset, the device shows up as a CAN interface (gs_usb). If JP4 is closed, it appears as a USB serial port (CDC) connected to USART1 for RS-485/RS-422 communication.
Anders notes that the board is essentially a simple STM32 development board with built-in industrial communication hardware, making it easy to reprogram. You can use it as a bus traffic generator, a CAN analyzer, or even turn it into an ST-Link–style programmer with custom firmware.
The hardware was designed in KiCad 9, and the complete design files (schematics, PCB layout, Gerbers, and BOM with LCSC part numbers) are available on GitHub under a CC BY-SA 4.0 license. The customized firmware is available in a separate GitHub repository.
The open-source FalCAN Probe with CAN and RS-485 is available for purchase on iMania.dk for 249.00 DKK (approximately $36 USD), with listed prices including 25% VAT for European buyers (VAT is removed at checkout for US/International buyers). It ships without the pin headers or the DE-9 connector soldered, though an unsoldered male DE-9 is included in the package so users can mount it on the bottom of the PCB to match the industry-standard TouCAN/PEAK CAN pinouts.
Debashis Das is a technical content writer and embedded engineer with over five years of experience in the industry. With expertise in Embedded C, PCB Design, and SEO optimization, he effectively blends difficult technical topics with clear communication
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