| With the development of the Automotive Electronics, the traditional communication such as"point to point"is getting more and more limited. Under this circumstance, the technology of Automotive Network has been created, of which the CAN-Bus is the most popular in the application. This paper is written for the automotive instrument with the CAN-bus function, to design a device to test its performance.Firstly,this paper showed the development of automotive instruments, and then followed by their corresponding test devices. We also gave the CAN-bus Protocol in detail.We gave basic principle of the design for this instrument. The writer proposed that it could be considered as"an advanced signal generator"which could generate test signal which is equal to it in an Auto. After received test signal, automotive instrument would also show the relative"information"as it in a car, and so we finished the process of test. Similarly, a device for testing a CAN-bus instrument is just a"signal generator"which could generate the CAN-bus signal.The model of the test instrument shows that it is composed of two main parts: hardware system and software system. The software system is just application software running in the PC and the hardware is only a circuit board based on a single chip. Through the Serial Communication, we could connect them, which realized the controlling the hardware by the application software which is operated by a man.The part of hardware system began with the introduction of single chip. We selected the MC9S12 Family MCU of FreeScale Company: MC9S12DJ64 MCU. In the hardware system , there are two main parts: design for a CAN-bus node and the Serial Communication Interface.For any CAN-bus node, at first, it should process the data according to the CAN-bus Protocol by a CAN-bus controller, and then convert it into the physical CAN-bus Differential signal through a CAN-bus transceiver. For the msCAN module has already been embedded in the MCU, we could only design a CAN-bus transceiver circuit to fulfill the creation of a CAN-bus node. Here we chose TJA1050transeicer of Philips Company.Although Serial Communication Interface has already been embedded in the MCU, it followed a standard in which 5V means the logic"1"and 0V logic"0". While Serial Communication Interface of PC, COM could not be compatible to the hardware system. In this reason, we should make use of another chip to carry it out. Finally we chose the chip of MAX232.After finishing the circuit board, we need burn the program in it. Because the hardware system would communicate with the PC by the Serial Communication, we must make some specific communication rules between them in order that they are able to"understand"each other when the communication is being. Every single step of test began in the PC, and the receiver must transmit a feedback command to make sure the process of communication safer.The induction of the program burnt into the hardware system is followed by this order: 1. Describe the function of every subprogram. 2. Show its flow chart. 3.Explain corresponding Register in detail. According to the hardware system, the burning program is also composed of two main subprograms: CAN-bus transmission sub function and SCI trans-receive sub function.The application software based on the PC was programmed by VB language. First, the writer showed the data formation in the software programming including Serial Communication part and internal storage data formation part. Later the paper told the reader how to realize the Serial Communication in the VB by using its controller MSComm. At last, it guided the reader to operate the software and gave the skeleton the programming concisely.Finally we carried out the full test process to test its performance. Fortunately, the device could do a good job when we input the information in the application software and it generated the right CAN-bus signal, by which the CAN-bus instrument could give the corresponding display.
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