CAN DB9 Pinout
CiA 303-1 standard 9-pin D-sub pinout for CAN bus and CANopen.
Overview
The DB9 (DE-9) connector is the de-facto physical interface for CAN and CANopen networks, defined by CAN in Automation recommendation CiA 303-1. It places the differential CAN pair and ground on a 9-pin D-sub for daisy-chaining.
Although the housing matches an RS-232 port, the pin assignments are entirely different - CAN and RS-232 cables are not interchangeable. Only a few pins are mandatory.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | Reserved | CAN | Reserved (optional CAN error line) |
| 2 | CAN_L | CAN / SIGNAL | CAN bus low signal line |
| 3 | CAN_GND | GND / CAN | CAN ground / reference |
| 4 | Reserved | SIGNAL | Reserved |
| 5 | CAN_SHLD | GND / CAN | Optional shield connection |
| 6 | GND | GND | Optional ground |
| 7 | CAN_H | CAN / SIGNAL | CAN bus high signal line |
| 8 | Reserved | CAN | Reserved (optional CAN error line) |
| 9 | CAN_V+ | POWER / CAN | Optional external bus power supply |
Notes
- Mandatory signals: CAN_H (7), CAN_L (2), CAN_GND (3).
- 120 Ohm termination belongs at the two physical ends of the bus.
Reference: CiA 303-1 - CANopen DB9 connector pinout· verified 2026-06-27