Controller Area Network (CAN) and RS485 (EIA/TIA-485) are two widely used serial communication protocols in industrial and automotive applications.
CAN is a robust, priority-based bus standard (ISO 11898) designed for real-time control systems, while RS485 is a differential signaling standard supporting multi-point communication over long distances.
This comparison highlights their technical differences, use cases, and trade-offs.
Contents
2. Technical Specifications
| Parameter | CAN (ISO 11898) | RS485 (TIA-485) |
|---|---|---|
| Physical Layer | Differential (CAN_H/CAN_L), 2.5V bias, 1.5V swing | Differential (A/B), ±1.5V to ±5V swing |
| Topology | Linear bus (terminated at both ends) | Bus, star, or daisy-chain (termination optional) |
| Max Nodes | 110 (theoretical), typically 20-30 | 32 (without repeaters), up to 256 with drivers |
| Speed vs. Distance | 1 Mbps @ 40m, 125 kbps @ 500m | 100 kbps @ 1200m, 10 Mbps @ 10m |
| Data Framing | Packet-based (ID, DLC, data, CRC) | Byte-stream (protocol-agnostic) |
| Arbitration | Non-destructive bitwise (ID priority) | Master-slave or peer-to-peer (collision-prone) |
3. Strengths & Weaknesses
CAN
- Pros:
- Built-in error detection (CRC, ACK, frame check)
- Deterministic latency (priority-based arbitration)
- Fault confinement (automatic node shutdown)
- Standardized higher-layer protocols (CANopen, J1939)
- Cons:
- Lower bandwidth (1 Mbps max for Classic CAN)
- Complex software stack (requires CAN controller)
- Higher transceiver cost (vs. RS485)
RS485
- Pros:
- Long-distance support (1200m+)
- Higher speeds at short distances (10 Mbps)
- Simple hardware (UART-compatible)
- Lower cost per node
- Cons:
- No built-in error handling (relies on protocol)
- Collision risk in multi-master setups
- No native prioritization
4. Real-World Applications
CAN Dominates:
- Automotive: ECUs, OBD-II, brake-by-wire (ISO 11898-2)
- Industrial: Robotics (CANopen), marine (J1939)
RS485 Preferred:
- Industrial Automation: PLCs, Modbus RTU, HVAC systems
- Building Systems: Lighting control, access panels
5. Decision Guidelines
Choose CAN if:
- Real-time fault tolerance is critical (e.g., automotive safety systems)
- Priority-based message handling is needed
- System requires ISO-standardized higher layers (e.g., CAN FD for >1 Mbps)
Choose RS485 if:
- Long-distance wiring is required (e.g., factory sensor networks)
- Cost sensitivity is high (low-cost transceivers)
- Legacy protocols (Modbus) are already in use
6. Conclusion
CAN excels in mission-critical, real-time systems with built-in robustness, while RS485 is ideal for cost-sensitive, long-distance applications with simpler protocols.
Future trends: CAN FD (5 Mbps) is bridging the bandwidth gap, but RS485 remains relevant for legacy industrial systems. Emerging Ethernet-based standards (EtherCAT, Ethernet/IP) are displacing both in high-speed apps.
