Can basic knowledge

The Can:controller area Network is an ISO-standardized serial communication protocol.

The can controller determines the bus level based on the potential of the two wires. The bus electric divide is the dominant level and the recessive level, caricatures. The sender sends the information to the receiver by changing the bus level.

In the can protocol, all messages are sent in a fixed format, and when the bus is idle, all units connected to the bus can start sending new messages. When more than two units start sending messages at the same time, the identifier ID determines the priority. The ID does not represent the destination address of the send, but rather the priority of the message that accesses the bus. When more than two units start sending messages at the same time, each bit of each message ID is compared to a quorum-by-arbitration basis. The winning unit of the arbitration can continue to send a message, and the unit that loses the quorum immediately stops sending and receives the job.

Can communication is done through 5 types of frames:

A data frame used to send a cell to a receiving unit to transmit data to a frame.
A remote control frame for the receiving unit to request data from a sending unit with the same ID.
An error frame used to notify the wrong frame to other units when an error is detected.
Overload frame for the receiving unit to notify the frame that it is not ready to receive.
Frame interval, a frame that separates the data frame and the remote control frame from the previous frame.

Bit timing:

The number of bits per second sent by the sending unit in a non-synchronous condition is called the bit rate. A bit can be divided into 4 segments

Sync Segment SS
Propagation time period PTS
Phase Buffer Segment 1 PBS1
Phase Buffer Segment 2 PBS2

These segments are made up of the smallest units of time that can be called the TQ (Quantum).

The so-called sampling point is the point that reads the bus level and reads the level as a bit value. The position is at the end of the PBS1.

Can bus idle is in hidden level.

Can basic knowledge