A CAN bus simulator with real firmware on every node

LabWired joins several simulated MCUs on one CAN bus. Each node runs its own firmware against a modelled CAN controller.

In the lab below, three Blue Pills exchange engine RPM and a synthetic temperature at 500 kbit/s. A companion lab adds a node built for 250 kbit/s, which goes bus-off.

Live lab, running in your browser. Open the full lab →

What is simulated

• STM32F103 bxCAN: three TX mailboxes, RX FIFO0, loopback, and acceptance filter banks. A frame no active filter matches is dropped, as on the chip.
• On a timed bus a frame takes wire time. Lost arbitration, TX errors, REC/TEC counters, error warning, error passive and bus-off are reported in ESR.
• Bus-off recovery, with or without MCR.ABOM.
• STM32H563 FDCAN is driven by firmware in CI.

What is left out

We list the gaps so you know when to reach for a bench.

• bxCAN RX FIFO1 is never queued. TSR.LOWx, silent mode (SILM), and the sleep and wake-up interrupts are not modelled on the timed bus.
• CAN transceivers (SN65HVD230 and the generic part) are wiring only: no analog bus levels, slope control or standby pin.
• The MCP2515 is an SPI register shell. Its CAN wire frames are not modelled.

Sources

Checked on 22 October 2026 against:

• bxCAN model (source)
• Firmware-exercise matrix (generated, CI-gated)

Related

• SN65HVD230 part page
• MCP2515 part page
• Catching a CAN bug that only shows up on real hardware

Other simulators

• nRF52840 simulator
• STM32 Nucleo simulator
• STM32 Blue Pill simulator
• Modbus RTU simulator
• Raspberry Pi Pico simulator
• ESP32-C3 simulator
• SSD1306 OLED simulator
• DHT11 simulator
• Servo simulator