How to connect the CAN bus What is the CAN bus?

The positive pole of the power supply of the equipment is connected to the constant power on the car (normal power refers to the wiring harness that has a power supply when the main switch of the battery is turned on); The negative pole of the power supply is used to connect the car battery.

Negative pole, ACC connected to the car key ACC power supply.

Check that the CAN cable is docked:

After the device is connected, turn on the ACC power to start the device, and start the car, then press the device menu key, and then press the turn button to press the system self-test, press the confirm button to confirm, enter the CAN information, if the customer has provided the CAN protocol and has been debugged, then you can see the car speed, battery voltage, oil temperature and other information, if not, you need to check whether the CAN cable is connected normally.

cnacan bus.

It was originally designed by the German company Bosch for automotive detection and control systems. In 1993, CAN became the international standard ISO11898 (high-speed application) and the specification developed from a specification (standard format) to a compliant specification specification (standard format, extended format), and most of the CAN devices currently in use comply with the specification.

<> in accordance with ISO 11898, in order to enhance the reliability of CAN-BUS communication, termination matching resistors (120) are usually added to the two endpoints of the CAN-BUS network. The size of the termination matching resistor is determined by the characteristic impedance of the transmission cable, for example, if the characteristic impedance of a twisted pair is 120, then the two endpoints on the bus should also integrate 120 termination resistors. I used a CAN to serial port device manual in the recommended topology diagram of a CAN bus device connection, you can refer to the following, when using in the field, the branch line should be as short as possible.

CAN is the name given to an industrial fieldbus. This interface is not available on ordinary computers. It is a serial communication method, but it is not a serial port. The appearance of the interface can be a 15-pin D-shaped port or an RJ45 interface, depending on what occasion it is used.

Features of CAN:

1. Strong real-time data communication between nodes in the network

The CAN controller works in a variety of ways, and each node in the network competes to send data to the bus in a lossless structure, bit by bit, according to the bus access priority.

And the CAN protocol abolishes the station address coding, and replaces it with the encoding of the communication data, which can make different nodes receive the same data at the same time, and these characteristics make the data communication between the nodes of the network composed of the CAN bus strong in real time, and is easy to form a redundant structure, improves the reliability of the system and the flexibility of the system.

2. Short development cycle:

The CAN node has an automatic output shutdown function in case of severe errors, so that the operation of other nodes on the bus is not affected, so as to ensure that there is no "deadlock" state of the bus due to problems with individual nodes in the network.

Moreover, CAN has a complete communication protocol that can be implemented by the CAN controller chip and its interface chip, which greatly reduces the difficulty of system development and shortens the development cycle, which is incomparable with RS-485 with only electrical protocol.

3. The fieldbus that has formed an international standard:

Compared with other fieldbuses, CAN bus is a fieldbus that has formed an international standard with many characteristics such as high communication rate, easy implementation, and high cost performance. These are also important reasons why CAN buses are used in many fields and have strong market competitiveness.

Compared with the general communication bus, the data communication of the CAN bus has outstanding reliability, real-time start-up and flexibility. It is the most widely used in the automotive field, and some of the world's famous automobile manufacturers have adopted CAN bus to realize the data communication between the internal control system of the vehicle and the various detection and actuators.

At the same time, due to the characteristics of the CAN bus itself, its application scope is no longer limited to the automotive industry, but to the automatic control, aerospace, navigation, process industry, machinery industry, textile machinery, agricultural machinery, robots, CNC machine tools, medical equipment and sensors and other fields. CAN has developed an international standard and has been recognized as one of the most promising fieldbuses.

The CAN-H line and the CAN-L line are two communication lines in the Controller Area Network (CAN), and they have the following differences:

1.Signal level: The signal level of the CAN-H line and the CAN-L line are complementary.

On the CAN bus, when the voltage on the CAN-H line is higher than the voltage on the CAN-L line, logic 1 is described; When the voltage on the CAN-L line is higher than the voltage on the CAN-H line, it indicates logic 0.

2.Transmit data: The CAN-H line and CAN-L line are complementary bits for transmitting data, respectively. For example, if the CAN-H line transmits logic 1, then the CAN-L line transmits logic 0.

3.Functional differences: CAN-H line and CAN-L line have the same function when transferring data, but have different roles in different devices.

In some devices, the CAN-H line plays the main control role, while the CAN-L line plays the slave role; In other devices, the roles of these two lines may be reversed.

In general, CAN buses use complementary signal levels of CAN-H lines and CAN-L lines to transmit data, and they play different roles in different devices but have the same function when it comes to transmitting data.

CAN is the abbreviation of Controller Area Network, which is an ISO international standardized serial communication protocol. Its full English name is Controller Area Network, which is generally abbreviated as developed by Bosch Company of Germany, which is known for its R&D and production of automotive electronic products, and eventually became an international standard (ISO 11898), which is one of the most widely used fieldbuses in the world.

In the automotive industry, a variety of electronic control systems have been developed in order to meet the requirements for safety, comfort, convenience, low pollution, and low cost. Due to the different types of data used to communicate between these systems and the requirements for reliability, there are many cases where multiple buses are constructed, and the number of wiring harnesses increases.

In 1986, in order to meet the needs of "reducing the number of wiring harnesses" and "high-speed communication of large amounts of data through multiple LANs", Bosch, a German electrical manufacturer, developed a CAN communication protocol for automobiles. Since then, CAN has been standardized with ISO11898 and ISO11519 and has become a standard protocol for automotive networks in Europe.