CAN Protocol Interview Questions

Controller Area Network or CAN protocol is a standard for communication between various electronic devices like engine management systems, active suspension, ABS, gear control, lighting control, air conditioning, airbags, central locking, etc which is embedded in an automobile.

The list of major features of CAN Protocol are as follows:

• Speed
• Flexibility
• Low Cost
• Robustness
• Built-in Error Detection

Some Listed applications of CAN Bus are as follows:

• Pedelecs
• Building automation
• Agricultural equipment
• Elevators, escalators
• Medical instruments and equipment
• Industrial automation and mechanical control
• Industrial automation and mechanical control
• Trucks, buses, Passenger vehicles, gasoline vehicles, and electric vehicles

It is a message-based protocol, originally designed for multiplex electrical wiring within automobiles to save on copper.

The CAN Messages types are listed below:

• Data frame - Data frame is a frame containing node data for transmission.
• The error frame - Error frame is a frame transmitted by any node detecting an error.
• The remote frame - A remote frame is a frame requesting the transmission of a specific identifier.
• The overload frame - An overload frame is a frame to inject a delay between data or remote frames.

High Speed CAN:

High Speed CAN offers baud rates (from 40 Kbit/s to 1 Mbit/sec) which is depending on cable length. It has the most popular standard for the physical layer. it allows for simple cable connections between devices. It is the physical standard used in the DeviceNet and CANopen specifications.

Low Speed/Fault-Tolerant CAN:

It offers baud rates (from 40 Kbit/s to 125 Kbits/sec). It is also a standard that allows CAN bus communication to continue in case of a wiring failure on the CAN bus lines. In the low speed/fault-tolerant CAN network, each device has its own termination

"CAN base frame" supports a length of 11 bits for the identifier which is made up of the 11-bit identifier whereas "CAN extended frame" supports a length of 29 bits for the identifier which is made up of an 18-bit extension.

CAN arbitration refers to the process in which two or more CAN controllers agree on who is to use the bus.

SAE stands for Society of Automotive Engineers. SAE J1939 is the vehicle bus recommended standard basically used for communication and diagnostics among vehicle components.

ISO11898 stands for the international standard organization standard for high-speed CAN communications in road vehicles. It also specifies the PMA and MDA sublayers of the Physical Layer.

CANopen is a high-level communication protocol and also a device profile specification that is based on the CAN (Controller Area Network)protocol. This protocol was developed for embedded networking applications, such as in-vehicle networks. It also covers a network programming framework, device descriptions, interface definitions, and application profiles. CANopen provides a protocol that standardizes communication between devices and applications from different manufacturers.