The Design And Implementation Of In-vehicle MOST Control Node

With the development of electronic technology, the number of the in-vehicle electronic devices is growing. The traditional link way has the disadvantage of high quality, high cost, EMI and etc. So, vehicle companies divide in-vehicle electronic system into some subsystems, there are particular electronic devices in these subsystems, the subsystem is the in-vehicle bus. The in-vehicle bus is a kind of key technology of the in-vehicle electronic technology.Now, CAN bus and LIN bus are the popular in-vehicle bus. CAN bus has the advantage of high responsiveness, high reliability. Although low speed, low responsiveness, but LIN bus has the advantage of low cost. With the growing of the number of in-vehicle entertainment devices, these two kinds of bus can not adapt the demand of high bandwidth, low EMI when transporting the media data. So Daimler-Chrysler, BMW, Hammer-baker, OASIS company develop the MOST bus with the advantage of high bandwidth, low EMI, low cost. The MOST Network is a kind of entertainment bus. It can transport the audio data and the video data. With the development in this decade, MOST technology became more and more popular. Now, European market is the main part of the market using MOST technology, Asian market and North American market also accept MOST technology gradually.In the modern times, MOST bus adapts the standard of MOST25. MOST bus uses POF, the bandwidth of the first generation MOST bus is 25Mbit/s. There has been the vehicle with the second generation MOST bus-MOST50. MOST50 use STP, the bandwidth is 50Mbit/s. the bandwidth of MOST50 is twice as wide as MOST25's. MOST company develops the third generation MOST bus in 2008, the bandwidth of MOST150 is 150Mbit/s. MOST bus is a new type of in-vehicle bus, many vehicle companies and vehicle research institutions pay close attention to it.Because the vehicle industry in our country is dropped behind in the field of in-vehicle electronic technology, our country can not develop MOST bus now. We must import MOST devices, and then assemble them. With the development of our vehicle market, the electronic technology of our country becomes the growth point of the world's vehicle technology. So when MOST technology extends in Asian vehicle market, studying MOST technology, develop MOST devices with intellectual property right is meaningful to our vehicle electronic technology.With the project to research and develop the in-vehicle MOST technology with China FAW Group Corporation R&D Center and the project to develop the in-vehicle entertainment system based MOST bus with the HSHY Company in Jilin, this paper bases on the MOST transport principle, designs the software and hardware of a MOST Network controller node. This paper is the base of following research.This paper analyzes the basis structure of the MOST Networks, the model of Network, the structure of data frame, transport protocol and etc, and this paper also illustrate the way of transporting data in the MOST Network. Compared the feature of all kinds of chips, this paper has chose the Network Interface Controller and external control chip.Network Interface Controller OS81050 has four external ports. The Network port is the interface between OS81050 and MOST Networks. Control port can transport the control data and the packet data. Streaming port can transport the streaming data. MediaLB port can transport all types of data. So there are two different ways to communicate between Network Interface Controller and external control chip. Compared MediaLB way with I 2 C way, this paper chose I 2 C way to complete the communication.MOST controller node can control the whole network. Compare to other nodes, the controller node pay attention to deal with control data. So MOST controller node has three functions: initial the node, transport and receive data with I 2 C bus, deal with control data. The hardware design of MOST control node is mainly around the Network Interface Controller OS81050 and the external control chip. The general programming chose OS81050 as the Network Interface Controller, Atmega128 as the external control chip. So this paper expanded circuit of the chip with the basic circuit of these chips. Then wire the PCB, we complete the hardware design.MOST control node is mainly used to control the whole network. When designing the software, the software programs of MOST nodes include initialing nodes, designing a interface between the I 2 C communication and the high level Network Service, designing a low level driver to transport or receive data on the I 2 C bus, designing a Network Service program which can convert high level commands to low level messages, or convert low level messages to high level commands or status.In this paper, we divide the Network Service program into two parts: low level Network Service program and high level Network Service program. The low level Network Service program faces Network Interface Controller. It can deal with low level messages. The high level Network Service program is above the low level Network Service program. It faces applications, and can provide applications with some API functions about Network Service. When transporting or receiving messages, applications need not realize the transport mechanism. Applications only use the API functions about Network Service to complete the communication.This paper divide the debugging into two parts: debugging the MOST control node and debugging the whole network. When debugging the MOST control node, we must ensure that the control node can completely initial, and can transport or receive messages normally. When debugging the whole network, we must ensure MOST nodes can work with each other, and complete the communication. After debugging, MOST Networks can work normally, and the whole system can run stably. So we can confirm that this design is successful.This paper has designed a MOST control node successfully. All nodes in the network can work with each other. So we can find that MOST bus has the advantages of high speed, high responsiveness, high reliability, anti-interferences. This paper becomes foundations and theory for applying MOST to in-vehicle multimedia, smart home.