There's LIN (Local Interconnect Network) communication, which always accompanies CAN (Controller Area Network) communication in automobile specifications. Its name does sound rather elegant, doesn't it?
explain
LIN(Local Interconnect Network) communication is a communication protocol used for various active sensors* and actuators within a car to communicate with control units. It is primarily used for low-speed communication within the vehicle and serves as a simple and relatively inexpensive communication solution that finds utility in many applications.
*Explaining it this way might still make it difficult to understand the difference between CAN communication.
Firstly, it's essential to understand that both CAN and LIN communication are not remote control communications. Both are used for communication among various control units and sensors inside the vehicle.
CAN communication is primarily used for communication among the core systems of a car, such as the engine, transmission, airbags, safety systems, etc.
Its features include:
- Capable of high-speed and reliable communication.
- Suitable for real-time data transmission requiring high speed and reliability.
- Supports complex network structures and long transmission distances (not wireless).
- Embedded with error detection and recovery mechanisms to ensure the safety of the vehicle.
<Core>
LIN communication is primarily used for communication among low-speed and relatively simple components within a car, such as active sensors and infotainment systems, which perform relatively simple functions.
Its features include:
- Low cost and simple implementation.
- Used for communication between components requiring low-speed data transmission.
- Relatively lower communication speed and reliability compared to CAN communication.
<easy explain>
CAN communication is a method used for important components in a car to communicate rapidly.
For example, when the engine and brake system exchange information, it needs to be fast and reliable. Hence, CAN communication is utilized. It plays a crucial role in situations like sudden stops or engine halts.
LIN communication, on the other hand, is used for relatively slow and simple communication between car components.
For instance, it can be used to control functions like the radio or window switches inside the car. These functions, such as turning the radio on or off, raising or lowering windows, or maintaining coolant temperature based on the car's temperature detection, don't require high-speed communication. Hence, LIN communication, which is relatively cheaper and easier to implement, is suitable.
(It's worth noting that when we say LIN communication is relatively slow, it doesn't mean slow as perceived by humans but rather slower compared to CAN communication. The speed of LIN communication is much faster than a human's perception of a second.)
※ CAN Communication Speed
Typically ranges from 125 Kbps to 1 Mbps.
125 Kbps means 125,000 communications occur per second.
1 Mbps means 1,000,000 communications occur per second.
※ LIN Communication Speed
Usually specified in the range of 1 Kbps to 20 Kbps.
1,000 to 20,000 communications occur per second.
(Additionally, the communication speeds mentioned above represent typical scenarios, akin to a standard normal distribution. It's essential to thoroughly understand and study your specific application before applying them, as there might be exceptional situations requiring different considerations.)
Continuing with LIN communication, as mentioned earlier, it's primarily used for communication with active sensors.
So, what are active sensors?
-> Active sensors refer to sensors that generate signals autonomously after being energized with electricity.
- Speed Sensor: Measures the speed of a vehicle. Typically attached to wheel hubs or transmissions.
- Temperature Sensor: Measures the temperature of various components in a car. For example, it monitors engine temperature to control its operation.
- Pressure Sensor: Measures pressure, such as fuel pressure or tire pressure, providing warnings to the driver.
- Inclinometer Sensor: Detects the inclination of a vehicle, providing information to various stability control systems.
So, what are passive sensors?
-> Passive sensors refer to sensors that require external intervention to detect changes in the environment or collect data. They are typically operated or controlled by humans or other external physical factors.
- Switches: Used to turn various devices in the car on and off. Examples include light switches or window switches.
- Pedals: Sensors operated by the driver's actions, such as the accelerator pedal or brake pedal.
- Steering wheel: Similar to pedals, sensors operated by the driver's actions.
- Buttons: Used to control various functions within the vehicle. Examples include buttons for the air conditioning system or radio AVN controls.
Furthermore, LIN is a single-wire bus system that operates on the master-slave principle. In a LIN data bus system, up to 16 slave ECUs can be connected to one master ECU.
<LIN Bus System Data Protocol>
The data protocol of the LIN bus system consists of [Message Header] and [Response].
Message Header
It plays a role in transmitting information from the master ECU to the slave ECU, and it consists of three elements:
① Start bit: Signals the start of a new message.
② Synchronization: Synchronizes all ECUs to operate at the same speed, ensuring timing alignment.
③ Identifier: Distinguishes each message, allowing precise recognition of the message.
Response
① When the master ECU requests actual values or diagnostic data, the slave ECUs respond. For commands to execute functions, the master ECU receives the response.
② The response includes precise information about the command to be executed. Slave ECUs do not transmit data in response to this message.
<Summary>
[Message Header] facilitates communication between the master ECU and slave ECUs, while [Response] performs tasks requested or provides data.
That's all.
