The Data Acquisition Based On LIN Bus

Developmentofautomobiletechnologymoreandmoreembodyinthefieldofthe automobile electronic, the traditional technology of automobile electronic isonly limited to electro-control about some mechanical spare & components in theautomobile, which is simple comparatively, and the relevant equipment is huger.This technology is backward comparatively. According to the need that the actualapplication of automobile is changeable, the modern technology of automobileelectronic majorization & synthetically control about automobile entiretyperformance by utilizing utmost develop's computer technology, networkcommunication technology and control technology. The modern automobileelectronic's technology has already changed to integrated electronical, intelligent,modules with integrated automobile; the bus-based controller network technologyisanewdevelopmentdirectionofthetechnologyofanautomobileelectronic.TechnologyoftheFieldBusCAN(ControllerAreaNetwork),whichappearedin the 80's of the 20th century and has greatly promoted the development ofmodern automobile electronics' technology. CAN Bus has gained the advantagethat other field buses can't contend against at the application field of automobileelectronicwithitspeculiardesignideaforautomobile.Now,atleastoneCANBussystem are equipped on almost all the European & American automobiles.However,theprojectcostofCANBusnetworkisveryhigh,andusingCANBuson some position with less important of the automobile is seemed "waste one'stalent on a petty job", and then which will increase the complexity ofcommunication among the bottom equipment sometimes. In this case, as thesub-busofCAN,LINBusarisesatthehistoricmoment.LIN (Local Interconnect Network) Bus is a one-wire series communicationnetwork with low cost. LIN communication is based on SCI(UART) data format,it adopt the mode of one-master controller / multi-slave equipment,which canavoid the bus message competition by only using the one 12V signal wire on physical. LIN message transfer rate can reach 20Kbit/s maximatily, user mayincrease the node in the network without hardware and software to need change.Generally,thenumberofnodeinaLINnetworkislessthan12.LIN Bus can beused torealizingthe distributed electronic control system inthe automobile. Because the LIN Bus goal is to offer the auxiliary function forexisting automobile network (for example: CAN Bus), So LIN Bus belongs to akindofauxiliarybus network. Insomeoccasionthat donot needthebandwidthofCAN Bus and multi-functional, such as the communication between intelligencesensor and the brake devices, using LIN Bus can greatly save the cost. Theappearance of LIN Bus enable people adopt the low cost solution to supplementthedeficiencyofCANBus.Vehicle in the course of the exercise, data is continuously changing, many ofthemarehigh-speedchanges,suchasspeed,enginespeedetc.Data acquisition is bridges to link automobile and body inside & outside'senvironment and is an important way to obtain information for automobile, toprovide immediately and effective information for control the vehicle. About thehigher accuracy & speed data acquisition, it can be used to CAN bus to achievetransmission. On the contrary if not require the more higher accuracy and speeddata acquisition, such as car inside & outside temperature and humidityetc, whichis not need high amount of real-time requirements, then introduce the LIN bus, soitcansatisfytherequestandthecheappriceandthehighreliability.WithLINBusintroduced, the diverse car body network has added that the body control systemdesign flexibility to improve the system reliability, so that conducive to thedevelopmentofdistributedcontrolsystemsbody.Theexperimental project baseonthe"Vehicle InformationSystem Platform ",there is a function demand which had been put forward to aimed at LIN busapplication, mainly design and improvement occasion which is related to simplevehicleanddemandmorelowtransmissionspeed.LIN bus is the application's main vehicle is simple, on the occasion of transmissionspeedmodestdesignandimprovement.In detail realize, after catch hold of testing object performance, then sure thatthis design need to achieve and realize function. On this basis, the experimentalwill be analyze about system program and definite system's network structure andaccording to the actual situation to definite hardware chip and development tools,and the key to this design: diagram of the hardware design, software codecomposeanddebugging.Generally, the car needs to be deal with the following three categories: switchsignal, analog signal and digital signal. LIN Bus more use about switch in theacquisition, such as car light, car door. But LIN Bus less use in the amount ofanalogand digital acquisition. The experiments mainlygather analog capacityanddigitalcapacity,andthedatacollectedthroughtheLINBustunnelshow.In this design, the mainly hardware chip adopt low-power & low voltage &high-performance 8-bit (i.e. AT89S51) of ATMELCo., then make the AT89S51as LIN network a MCU (Micro Controller), and the output of the functions &instructions systems compatible with MCS-51, more flexible and inexpensive,ISP support downloading. Make Philips's TJA1020 as LIN transceiver.Temperature sensor adopts from DALLAS Co product which is the digitaltemperature sensor DS18B20, simple interface, and the economy, which is typicalinthedigitalcollection.Achievinganalog-digital conversiondevices adopt from U.S.AsemiconductorCo product which is ADC0804. It is eight then successive approximation ADC,belongCMOSdevice.This paper present the main nodes from the drawings and designs, Choice ofdevelopment tools from the Shanghai Xingyan Co product which is SUPERICE16 as hardware simulator device, embedded Xingyan KEIL C integratedsoftwareasaPCsoftwarecompose&debuggingenvironment.Online real-time simulation, embedded system's development pattern will befollowed during the development process, all code use the C51 to prepare, adopt modular software design and have more better with consistency andtransplantation, then increase procedure more readability and understandability.The whole software is composed with Digital Temperature Acquisition Moduleand A/D conversion module and microprocessor module and LIN buscommunication module, total four parts module composed.Amongthem, LIN buscommunication module divided two parts: sending procedures and receivingprocedures.Complete all the design work, laboratory testing and field testing phase, andbetter achieving the collection and transmission of the functional requirements.PracticeshowedontheLINbusdataacquisitionisfeasibleandreliable.Atpresent,the paper merely demonstrate the feasibility on the basis of the experiments, thenext step will be for products, assemble test. LIN Bus no need more modules andno more cable, in the mean time through the LIN bus to test and debug. Authorizeor shielding some certain characteristics, it can bring a great deal cost savings fordevelopersandconsumers.About LIN Bus, not only in the field of automotive electronics, further on inthe public areas of consumer electronics and industrial control areas it will have abroaderapplication.