Unveiling the Power of CAN in Embedded Systems

Author : my internship | Published On : 14 Mar 2024

In the intricate world of embedded systems, communication is the key to seamless operation. One crucial player in this communication game is the Controller Area Network, or CAN. Let's demystify CAN, explore its working mechanism, understand its protocol layer, and uncover the number of channels it brings to the table.

What is CAN in embedded systems?

CAN stands for Controller Area Network, a communication protocol widely used in embedded systems for real-time applications.

How does a CAN system work?

CAN facilitates communication among microcontrollers and devices without a central computer.It employs a multi-master, multi-node approach, enabling simultaneous data transmission without conflicts.

What layer is CAN protocol?

CAN operates at the data link layer (Layer 2) of the OSI model.The two sub-layers within CAN are the Logical Link Control (LLC) and the Media Access Control (MAC).

Media Access Control (MAC):

Responsible for addressing nodes, error detection, and managing message priority. Implements a non-destructive bitwise arbitration mechanism, where the message with the highest priority gets transmitted first.

Logical Link Control (LLC):

Manages flow control, acknowledging received messages, and retransmitting if necessary. Enhances reliability by ensuring that the sender knows if the message was successfully received.

CAN Frame Structure:

Messages in a CAN network are called frames, consisting of an identifier, control bits, data, and CRC for error-checking. Two types of frames: Data frames carry information, and Remote frames request data from other nodes.

Bitrate and Timing:

CAN supports various bitrates, with common rates being 125 kbit/s, 250 kbit/s, and 500 kbit/s. Timing is crucial; nodes must synchronize to avoid conflicts, achieved through predefined time quanta.

Error Handling:

CAN employs sophisticated error detection mechanisms, including cyclic redundancy checks (CRC). Detected errors trigger an error frame, and faulty nodes are temporarily isolated to prevent disruptions.

How many channels are in CAN protocol?

CAN operates on a two-channel, twisted-pair wiring system: CAN High (CANH) and CAN Low (CANL).

CAN High (CANH):

Voltage Level: CAN High operates at a higher voltage level compared to CAN Low.

Transmission: During transmission, the voltage on the CANH wire increases, representing the dominant state.

Dominant State: In the dominant state, CANH voltage is closer to the supply voltage, indicating a logical 0.

CAN Low (CANL):

Voltage Level: CAN Low operates at a lower voltage level compared to CAN High.

Transmission: During transmission, the voltage on the CANL wire decreases, representing the dominant state.

Dominant State: In the dominant state, CANL voltage is closer to the ground, indicating a logical 0.

These channels allow for balanced communication, reducing electromagnetic interference.

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