Design Of Embedded Car Gateway Based On ARM9

With the rapid development of electronic technique and the continuity improvement of vehicle performance, the electronic equipments on vehicle are becoming more and more. Traditional electric systems mostly introduced point-to-point communication mode, little affiliation with them. That made the connection system complex. In order to adapt the development of the vehicle electronic equipment, the in-vehicle network system has come forth. For example, CAN bus, LIN bus and F1exRay have been applied in in-vehicle network system. Because of particular structure and stable performance of CAN bus, which applied in it is the most widely.CAN is a serial communication protocol which was declared by Bosch company. Compared with other kinds of field buses, CAN bus has low price and good performance. It saves lots of wirings because all of the CAN nodes are linked to the same bus. One message on CAN bus needn't be sent several times because it is transferred serially and so it is shared by all nodes. Messages of CAN have short frame, whose data field is composed of 8 bytes at most, as a result, every message is transmitted quickly on bus. Nodes in bus compete with each other for bus occupancy privilege when they are going to send message to others. CAN bus uses message coding instead of address coding, and its baud rate could reach 1Mbps. It also has advantages in error detection and self recovery, which evidently ensure the reliability data transmission. Lin bus is an more lower bus than CAN, it is applied in lower velocity environment as supplement of CAN bus.In recent years, a lot of automobile factories put their emphases on CAN researching and some of them have worked out products of CAN. We can infer easily that CAN bus would have bright future in the next few years.In order to managing the nodes of in-vehicle network efficiently and processing the data, I have designed the MCN(main control node) of the in-vehicle network. That is carried out by the S3C2410 MPU of ARM9 core, and the software platform is Embedded Linux.. The gateway process the communication with the CAN network and Lin network. There are four nodes in the CAN network, They are fixed separately in the four corners of vehicle, which are linked to many lights (such as high beam, passing lamp, turn light, emergency light, etc.).The LIN network also contains four nodes which are linked to different doors.Among the gateway circuit, the main chips in the CAN network are: S3C2410, MCP2510 and 82C251, the main chips in the Lin network are S3C2410 and TJA1020. Their characters and functions are shortly described in this paper. The circuit diagrams are also provided in detail. Samsung's S3C2410X is a 16/32-bit RISC microprocessor. This product is designed to provide hand-held devices and general applications with cost-effective, low-power, and high-performance microcontroller solution in small die size.To reduce total system cost, the S3C2410X includes the following Components separate 16KB Instruction and 16KB Data Cache, MMU to handle virtual memory management,Besides the existing physical layer protocol data link layer protocol, the application layer protocol should be defined according to the special purpose in this design. Eight different message IDs are used because there are eight kinds of light should be controlled. Those IDs present the meaning of messages, and they also denote the static priority of messages. One byte data is used in every message frame to denote the specified operation type to be done. When several nodes are sending messages to bus at the same time, the one whose message has high priority will get the access to use bus, and the others have to wait until the bus is free again. The gateway should control the four doors to open or close them. Every door is given signal address from oxc0 to 0xc3. Eight instructions are defined to control the doors. Thirty two instructions are defined to explain the feedback.Aside from the hardware circuit and the protocol definition, the software also plays a big part in this design. The software is programmed in CAN device drivers and Lin device drivers based on Linux. The application programmer also is realized based on drivers to communicate with CAN and Lin network. This design testifies the feasibility of using CAN bus and Lin bus to car body network. it provides the software and hardware environment of extending to the in-vehicle information center in the future. Besides CAN bus, this system used LIN bus into in-vehicle network, and present low cost CAN/LIN mix network architecture for vehicle. The wireless network part could be added in the future work, and we will put emphasis upon the research of communication between different bus network, such as MOST .