This recording instrument uses brings ARM7 essence LPC2104 CPU to make primarily controlling machine, large capacity dodges the fast memory to take the memory carrier, has the precise clock electric circuit, transforms the simulation quantity using the high accuracy A/D switch gathering automobile sensor, and direct recording automobile signal light and so on each kind of switch quantity. Simultaneously uses the string mouth realization and the microcomputer data communication, saves the automobile travel record low information by the binary file form to the hard disk on.

System overall frame like chart 1 shows. Brings ARM7 essence LPC2104 CPU is the automobile travel recording instrument core, the overall system by the information gathering module, the information processing and the memory module and the string mouth connection module is composed.

LPC2104 is a section support real-time simulation and track ARM7TDMI-S CPU which Philips Corporation produces, internal integration has with the internal memory controller connection ARM7 local bus, (AHB) and inside and outside the connection piece supposes the function with the interrupt controller connection AMBA high performance main line outside VLSI to suppose the main line (VPB, ARM, AMBA main line compatible ultra large scale integrated circuit), and has inserted 128KB the high speed Flash memory. LPC2104 the ARM7TDMI-S disposition for the small end (Iittle-endian) the byte order, has seals small, the power loss is low, many 32 timers, the many kinds of main lines connection and reaches merit and so on 9 external interrupts, extremely suits as the automobile travel recording instrument host controls CPU. At the same time, LPC2104 also has 128 widths the memory interfaces and the unique acceleration structure, thus enables 32 codes to be able to move under the biggest clock frequency.

2 information gathering module design

Automobile travel recording instrument request real-time recording vehicles travel each kind of condition information, therefore this system divides into the information gathering module the switch quantity data acquisition module, the simulation quantity data acquisition module, the clock data acquisition module.

2.1 switches quantities data acquisition module

This module parallel inputs 8 displacements positions register using 74LS165 bit parallel to expand 16 to lose the entrance, its hardware electric circuit like chart 2 shows. Is 16 loses the entrance line using the LPC2104 3 I/O mouth line expansion, in the chart expands 16 input lines by 2 piece of 74LS165 series connection, CLK is the clock pulse input end, D0-D7 is the parallel input end, first level data out-port QH is connected with latter level signal input end SIN, when S/L is the low level, the permission parallel sets at into the data, S/L is when the high level permits serial shifting. Like this about the direction lamp, front the headlight, opens the gate signal, the brake lamp signal and so on 16 groups switches quantities after the photoelectricity coupler isolation the parallel input to 2 piece of 74LS165 in, after again passes through the 74LS165 transformation, the serial output carries on processing to LPC2104.
2.2 simulations quantities data acquisition module

When carries on analog data gathering, the water temperature, the water level and so on 8 groups sensors gather the signal first recuperates the link after the simulated signal, its 整定 in A/D in the switch reference voltage Vref decision full measuring range input voltage signal, then carries on after the A/D switch the A/D transformation. This module uses TLC0838 8 groups 8 which the US Texas Instruments company promotes gradually to approach the mold, the number switch, the sampling frequency is 100kHz, uses the SPI main line connection with the external communication. LPC2104 the SPI main line connection and TLC0838 which inlays through among them carry on the correspondence, its hardware electric circuit like chart 3 shows. SCK is the SPI main engine input or from machine the input clock, MOSI is the SPI main engine to from machine the data transmission, MISO is SPI from machine to the main engine data transmission, SSEL is SPI from machine the choice.

The automobile speed survey is through counts the pulse signal realization which the velocity generator produces. This system counts the speed pulse signal using the AT89C2051 monolithic integrated circuit. This monolithic integrated circuit may establish to defend the guage to count the speed pulse signal, and transforms it the automobile the actual measuring range. Meanwhile may calculate the automobile according to the travelling schedule and the time the speed, and through string mouth UART0 data transfer for LPC2104.

2.3 clocks data acquisition module

For the recording driving time, enables the travel recording instrument the real-time recording automobile condition, uses the special clock module to provide the time signal, this system selects the DS12887 clock electric circuit. DS12887 is surmounts 2000 the clock electric circuit, uses 4 figures expressions year the calendar system. The electric circuit crystal oscillator, the oscillating circuit, the charging circuit and may charge the lithium battery and so on to seal together in the chip stops the side, composes a Canada thick integrated circuit module. DS12887 can automatically deposit and withdraw and the renewal current time, LPC2104 passable has read DS12887 internal time indice register to obtain the current time and the calendar, also passable has chosen two the code or the BCD code initialization electric circuit 10 time indices register.

3 information processing and memory module design

Because the Flash memory structure is suitable is the solid state saves, the EPROM memory structure is suitable to the dynamic storage, therefore, this system according to the actual need, the useful Flash solid state memory and the EPROM dynamic storage unifies the way carries on the data storage and remembered, namely saves gathering with the Flash solid state the automobile condition data, with EPROM dynamic storage Flash newest memory fan district number and memory address. Dodges the fast memory to select MX29F800BTC which the beautiful letter company produces, EPROM selects Microchip Corporation 24C32, simultaneously uses the I2C main line connection and 24C32 which in LPC2104 inlays carries on the correspondence.

When this system work, first controls CPU by the LPC2104 host to read from 24C32 takes the fan district number and the memory address which Flash recently saved, then take this address as the reference, take a this address address value as the Flash beginning address, take this address next address value as the Flash beginning address, carried on the memory according to the order. Flash needs to save the data has 16 groups switches quantities information, 8 groups simulations quantities information has and the clock information. This system uses two bytes (altogether 16) to save 16 groups switches quantities information, uses 8 bytes the storage spaces to save 8 groups simulations quantities information. In order to save the storage space, the system each time saves when by no means the gathering data all storage time symbol. Because the data acquisition is separated by the fixed second carries on, therefore, the system only was when just started the movement and each fan area reference gathering and the memory clock signal takes the timer, but behind the data gathering time take these timers as the reference.

The system saves software flow like chart 4 shows. When this system 重装 on electricity movement, needs start-of-record gathering the time information. Because the system power source is provides by the automobile power source, therefore starts the time which gathers also is the time which the automobile starts, starts the timer by this as the automobile which goes. In the procedure movement, establishes an automobile by the master routine to start the symbol, in first time writes in front of the data the automobile starts the sign to be effective, then first judges the current memory address whether has some fan area the first address, if is, then acts according to writes the fan area the request in the seventh byte start place memory current clock signal, otherwise, starts in the current memory address place with 10 bytes memories current clock signal, records outset time which the automobile starts to move, then eliminates the automobile to start the symbol. The fan area starts the address place recording time information whether is the outset time which the automobile starts to move, may act according to the preceding fan area recording the time information to carry on the judgement. If around two fans areas recording data is continual, then the latter fan area record time information is not expressed the automobile starts the outset time which moves, otherwise the situation is opposite.

4 strings mouths connection module design

The computer may read as necessary through the string mouth takes the data which the travel recording instrument saves. Between the travel recording instrument and the computer string mouth correspondence follows the RS232 agreement. When serial communication, LPC2104 in turn the data read-out and which saves Flash in sends out after the UART0 string mouth, then gives the computer after the MAX232 level switch, again receives this data by the computer through the string mouth.

5 concluding remark

The automobile travel recording instrument use microcomputer through the string mouth receive automobile travel data, and the logarithm according to carries on analysis processing; Using Visual C++ 6.0 took the development kit, compiles the microcomputer data analysis disposal procedure, the conformable display automobile moves the time condition; Using the graphical display various components profile, like front to the light switch situation, about the direction light switch situation, opens the gate information, the brakes signal, the water temperature change situation (scope is 0 �?~100 �? and so on. Installs this travel recording instrument on the automobile carries on the test, the result is also more ideal, can satisfy the design request. Its test result like chart 5 shows.