--- title: "CAN and LIN bus communication" subject: "Automotive Technology" chapter: 11 key: "semester_5/automotive_technology:can-and-lin-bus-systems" source: https://www.bctengineer.com/q/semester_5/automotive_technology/can-and-lin-bus-systems site: BCT Engineering --- # CAN and LIN bus communication Automotive Technology · Chapter 11: Automotive Electronics - Asked in: year not given, 6 marks - Video: [CAN Bus Explained - A Simple Intro [v1.0 | 2019]](https://www.youtube.com/watch?v=FqLDpHsxvf8) — CSS Electronics - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/automotive_technology/can-and-lin-bus-systems - Whole chapter: https://www.bctengineer.com/md/semester_5/automotive_technology/chapter-11 ## Question Why are in-vehicle networks used? Describe the CAN bus (structure, signal, message frame) and compare it with the LIN bus. ## Short answer In-vehicle networks reduce wiring by sharing data on a bus. CAN uses twisted pair, differential signaling, multi-master message frames with identifier, data, CRC at up to 1 Mbit/s. LIN is a low-cost single-wire master-slave bus at up to 20 kbit/s for comfort devices. ## Answer #### Need for in-vehicle networks A modern car has 50 to 100 ECUs (engine, ABS, airbag, body, infotainment). Connecting each pair with separate wires would be heavy, costly and unreliable. A **serial data bus** lets all ECUs share data over only two or a few wires, reduces weight and makes diagnosis easy. #### CAN (Controller Area Network) Developed by Bosch (ISO 11898). ```text ECU1 ECU2 ECU3 ECU4 | | | | ==== CAN_H ===================== ==== CAN_L ===================== 120 ohm terminator at each end ``` - Two twisted wires, **CAN-H** and **CAN-L**, carry a differential signal (dominant bit: H = 3.5 V, L = 1.5 V; recessive bit: both 2.5 V), so noise is rejected. - Speed is 125 kbit/s to 1 Mbit/s (high-speed CAN for engine and ABS). - **Message frame:** start bit, identifier (11 bits, showing content and priority), control field, data (0 to 8 bytes), CRC, acknowledge and end of frame. - It is multi-master: any node can send. **Arbitration** by the identifier is bitwise: the lower number wins, so there is no collision. Error checking is strong. #### LIN (Local Interconnect Network) A cheap, single-wire, master-slave bus for simple, slow devices such as mirrors, window lifts, seat motors and rain sensors. | Point | CAN | LIN | |---|---|---| | Wires | 2 (twisted pair) | 1 (plus ground) | | Speed | Up to 1 Mbit/s | Up to 20 kbit/s | | Control | Multi-master | One master, up to 15 slaves (16 nodes) | | Cost | Higher | Low | | Use | Engine, brakes, safety | Body comfort devices | LIN nodes connect to the CAN network through a gateway. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why are in-vehicle networks used? A. They increase the number of wires B. They replace the battery C. They remove ECUs D. A serial bus shares data among 50 to 100 ECUs over few wires, cutting weight and aiding diagnosis Answer: D. Point-to-point wiring is heavy, costly and unreliable. (Key point: Need) 2. How is the CAN signal carried? A. Optical B. Single wire, voltage to ground C. Differential on twisted CAN-H and CAN-L, so noise is rejected D. Radio waves Answer: C. A differential signal (dominant H 3.5 V, L 1.5 V) rejects noise. (Key point: CAN signal) 3. How does CAN avoid collisions? A. Time slots B. Higher number wins C. A master polls each node D. Bitwise arbitration on the identifier; the lower number wins Answer: D. Multi-master CAN uses the 11-bit identifier for priority. (Key point: Arbitration) 4. Which is correct for LIN? A. Used for ABS B. Two wires, 1 Mbit/s, multi-master C. Single wire, up to 20 kbit/s, one master with up to 16 slaves, for mirrors and windows D. Costlier than CAN Answer: C. LIN is a cheap slow body bus connected to CAN through a gateway. (Key point: CAN vs LIN) ## Related in Automotive Technology - [Electric vehicle architecture and traction motors](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Aev-architecture-and-motors) — Automotive Technology, chapter 12 ## Related in other subjects - [SSB wave for a low pass message signal](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Assb-lowpass-message) — Communication Systems, chapter 2 - [Message transfer parts and signal unit addressing](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Amtp-signal-unit-addressing) — Telecommunications, chapter 5 - [GSM frame structure, traffic and control channels](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Agsm-frame-traffic-control-channels) — Wireless Communication, chapter 8, asked 4× - [GSM frame structure and channels during a call](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Agsm-frame-call-channels) — Wireless Communication, chapter 8