Understanding CAN Bus Protocol in Vehicle Telematics
CAN Bus (Controller Area Network) is a robust communication protocol that has revolutionized vehicle telematics. In this article, we explore the technical details of this fundamental protocol.
What is CAN Bus?
CAN Bus is a serial communication standard designed by Bosch in the 1980s. Originally created for the automotive industry, it has expanded to industrial, aerospace, and medical applications.
Key Features
- Multi-master architecture: Any node can initiate communication
- Priority-based messaging: Higher priority messages are transmitted first
- Error detection: Built-in mechanisms for data integrity
- High noise immunity: Differential signaling for robust communication
How Does It Work?
Physical Layer
CAN Bus uses two wires:
- CAN-H (High): Carries the dominant voltage
- CAN-L (Low): Carries the recessive voltage
The difference between both signals determines if the bit is dominant (0) or recessive (1).
Data Frame Structure
A standard CAN frame includes:
| Field | Bits | Description |
|---|---|---|
| SOF | 1 | Start of Frame |
| Identifier | 11/29 | Message ID (priority) |
| RTR | 1 | Remote Transmission Request |
| IDE | 1 | Identifier Extension |
| DLC | 4 | Data Length Code |
| Data | 0-64 | Actual data payload |
| CRC | 15 | Checksum for error detection |
| ACK | 2 | Acknowledgment |
| EOF | 7 | End of Frame |
CAN Bus in Vehicles
Standard Parameters (OBD-II)
Common parameters accessible via CAN Bus:
- Engine RPM (PID 0x0C)
- Vehicle Speed (PID 0x0D)
- Fuel Level (PID 0x2F)
- Engine Coolant Temperature (PID 0x05)
- Throttle Position (PID 0x11)
- Engine Load (PID 0x04)
Proprietary Parameters
Vehicle manufacturers often include additional parameters:
- Total fuel consumed
- Detailed diagnostic codes
- Transmission data
- Safety system status
Rinho Telematics and CAN Bus
All Rinho devices include native CAN Bus support:
Spider IoT
- Single CAN channel
- Automatic protocol detection
- Compatible with most vehicles
Smart IoT
- Dual CAN channels
- J1939 support for heavy vehicles
- Extended parameter extraction
Benefits for Fleet Management
- Accurate fuel monitoring: Read actual fuel level from vehicle ECU
- Real odometer: Obtain manufacturer's odometer reading
- Engine diagnostics: Detect problems before failures occur
- Driver behavior: Analyze RPM, harsh braking, acceleration patterns
Technical Implementation
Connection Points
CAN Bus can be accessed via:
- OBD-II port: Standardized connector (vehicles post-2008)
- Direct ECU connection: For older vehicles or custom applications
- Diagnostic connectors: Manufacturer-specific ports
Baud Rates
Standard CAN baud rates:
- 250 kbps: Common for older vehicles
- 500 kbps: Most modern passenger vehicles
- J1939 (250 kbps): Heavy vehicles and trucks
Conclusion
CAN Bus technology is essential for advanced vehicle telematics. Rinho devices leverage this protocol to provide comprehensive fleet management data.
For more information about our CANBUS solutions, contact us.