The Design Of Embedded Software In Car Audio And The Implementation Of Display Function

With the development of automobile production industry and electronic industry, Car Audio system has been updated and consummated continuously. The first electronic product applied on Automobile is Car Audio. It has turned from primary Car Radio into comprehensive multi-media carrying electronic system and it has functions of seeing and hearing, amusement, navigation, auxiliary driving. And it is becoming an indispensable part of the Automobile of the future.Car Audio is one part of Automobile.Its mostly task is providing the consumers of enjoy of voice of highly quality while Automobile is on the rails. In the realization of this project, the M16C/62 series single chip C language is used. It adopts the most advanced data media technology referring to data signal processing and digital sound composing etc technology field nowadays. It has well security and replanting.The software and the hardware in the project are developed abreastly.The processor in the hardware is the M16 Cs/62s series single chip made in Japanese Mitsubishi company .Because its inner part is embedded a 16-bits processor, between 8-bits with 32-bits, its price is lower. It has many interfaces, and it can reach various technique indexs whicht he design request completely on the functions.On the software, the embeded application software is designed and developed based on the Japanese NEC company's MX_OS operation system. MX_OS is completely according to the iTRON norm from and developed by NEC Company independently. MX_OS has a small volume, and doesn't request the MCUs high, so the software can be planted to various MCUs. With these advantages, MX_OS is applied by in the industry controling, in the home appliances and in other electronics products in Japan. So we choose MX_OS as the operation system in the object. The embedded application software is the main mission that the embedded software developping. Because the application software in the project takes MX_OS as operate system, so the software is splitted into some molds, that is dividing the software into some function molds according to each functions of the software. The molds keep utmost independence each other. If the molds have connection with another, they can use the interface functions or interface datas (also be called to interface BUFFER) to realize their contact. The MX_OS usage event triggers and interruption triggers to carry on dispatching the application software, so each mold is as a task of MX_OS or as an inside interruption service sub- procedure. The system main clock's cycle of the processor is 4 millisecond, so each mold's minimum executing time cycle is limited within 4 millisecond. But the display mold is exceptted.The display modle is executed not as a mission in the thesis , but it is put into eight milliseconds cycle to be executed.At the same time, because the time that GRAPHIC mode from reading the datas , processing them,to display them over 4 milliseconds, the design is not agree with MX_OS's demand in real time operation system.To remedy this shortage, we use six 8-milliseconds to display a frame .That is ,the display time is divided into six 8-milliseconds to process displaying a frame.Firstly, Graphic reads the manifestation datas,and obtains the PID which is sended by the DMM mold, and analyzes the PID as the Source and the Mode;Secondly, according to the resolution of the Source and Mode establishs a good dynamic control data;Thirdly, calls the engine and puts the display data into the logic buffer;Fourthly, processes a special display function for the special PIDs;Fifthly, sends the display datas to the PT6523 chip;Sixthly, does nothing, but change the step mark with the first step.Because of the asynchronism when DMM and Graphic stores or reads the datas, causes some display BUG.In this thesis, Graphic mold contrasts the PIDs in the fore and the latter cycle to control its own display functions.In this way, display problems whith are caused by DMM and Graphic's asynchronism of stroing and read datas are eliminated.In the hardware, the PT6523 chip is used as the drive chip which is made by PCT company. The M16 Cs/62s single chip uses the fake COM port to send a display datas to the PT6523 chip. The single chip sending the datas to the PT6523 chip obeys the PT6523 data structure strictly, that is delivering the display datas and the control word after sending the PT6523's address. System defines a LCDDriver mold over the display hardware. And the LCDDriver is used as a transparent layer between the Graphic and the display hardware .Thus, this kind of design also matches the mold design thinking.