CAN message types and structure
In SPI communication, the four signals of chip select, clock signal, data input and data output have separate signal lines. The I2C protocol includes two signal lines for clock signal and data signal, and the asynchronous serial port includes two signals for receiving and sending. These protocols contain more signals than the CAN protocol, and they can easily synchronize data or distinguish the direction of data transmission.
However, CAN uses two differential signal lines, which can only express one signal. The concise physical layer determines that CAN must be equipped with a more complex protocol. How to use one signal channel to achieve the same or even more powerful functions? The solution given by the CAN protocol is to package data, operation commands (such as read/write) and synchronization signals, and these packaged contents are called messages.