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CAN Bus

Navigation: Configuration > IoT > Sources > CAN Bus

The CAN Bus page configures the CAN (Controller Area Network) interface of the IRF3851, used to acquire industrial data from a connected CAN bus. It sets the CAN bit rate, optional CAN FD (Flexible Data-rate) operation with its own data-phase bit rate, listen-only mode, bus-error reporting, and automatic bus-off recovery. The live interface status — bit timing, error counters, and controller mode — is shown on the State tab. Changes take effect after clicking Apply, but must be saved persistently via the Save page to survive a reboot.

Note

The CAN interface is available only on models equipped with CAN hardware (e.g. the IRF3851). On the IRF3851 the CAN bus shares a 12-pin connector with digital I/Os 3…5.

Use from Docker

The CAN bus can be accessed from Docker containers running on the device. Enable CAN access for containers on the Docker page.

CAN Bus

Settings

CAN 0 bitrate
The CAN 0 bit rate in bits/s (the arbitration-phase bit rate). It must match the bit rate of the connected CAN bus.
CAN 0 FD enabled
Enables CAN FD (Flexible Data-rate) for CAN 0. When enabled, the data phase uses the separate data bit rate below.
CAN 0 data bitrate
The CAN 0 data bit rate in bits/s for the data phase of CAN FD frames. Only used when CAN FD is enabled.
CAN 0 listen only
When enabled, CAN 0 only listens and does not send any frames or acknowledgments (passive monitoring of the bus).
CAN 0 bus error reporting
Enables bus-error reporting for CAN 0.
CAN 0 restart-ms
The automatic-restart time in milliseconds after a bus-off condition (0 disables automatic restart).

CAN connector and wiring

On the IRF3851 the CAN bus shares a 12-pin (2×6) connector with digital I/Os 3…5. The CAN signals are on pins 9–12; for the complete connector pin assignment see Electrical interfaces.

IRF3851 12-pin connector

Pin Signal Description
9 CAN_H CAN high line
10 CAN_L CAN low line
11 CAN_SHIELD Cable shield
12 CAN_GND CAN reference ground
  • Use a twisted pair for CAN_H (pin 9) and CAN_L (pin 10).
  • Connect CAN_GND (pin 12) to the CAN reference ground of the bus system.
  • Route the cable shield continuously and connect it to CAN_SHIELD (pin 11).
  • Use a linear bus topology; avoid a star topology and keep branch lines (stubs) as short as possible.

Termination

  • Fit 120 Ω termination resistors only at the two physical ends of the CAN bus.
  • An IRF3851 used as a mid-node must not add extra termination.

CAN bus wiring example

Commissioning checklist (physical connection)

  • CAN_H (pin 9) and CAN_L (pin 10) are not swapped.
  • CAN_GND (pin 12) is connected.
  • The shield is connected to pin 11.
  • Exactly two 120 Ω termination resistors are present, one at each bus end.