Author Email: greatchen1979@163.com
Introduction:
The current domestic main big city’s public transportation uses the artificial pronunciation newspaper station mostly, as soon as whenever namely stands by the driver or the train attendant commentary key carries on the newspaper station. But sometimes because receives on each kind of factor like sleet day Lu Hua, the vehicle crowded, the train attendant mood change and so on influence, can leave the retribution in this life wrong station, fails to report situation which stands, was specially not the familiar this city terrain passenger has brought the nonessential trouble for the passenger, thus has constructed the shade noon to a city’s window image project, therefore the development automatic newspaper station system became inevitably. In because the system request docking receives the public transportation GPS localization information (latitude and longitude information and so on) carries on processing, by between the latitude and longitude information production station sign and public transportation’s distance information, between this will experience the tedious computation, will difficulty with realize with the common micro controller, but when will use the DSP processing chip, this question is very good solves.
1. Automatic newspaper station system’s gross structure
The entire automatic newspaper station system mainly carries the equipment and the electronic station sign by the vehicle two major part is composed. System structure frame as shown in Figure 1.1. The vehicle carries the equipment mainly to use to the public transportation locator data extraction realizes the automatic newspaper station, but the station sign equipment mainly uses to this positional information demonstration. Because public transportation’s positional information is changes unceasingly, but the station sign position is relatively fixed, therefore between both must the establish contact, must establish in above the wireless communication foundation.
The automatic newspaper station principle is as follows: The vehicle carries the GPS receiver to receive public transportation’s localization information unceasingly, after undergoing DSP processor processing withdraws the useful information and through the wireless receiver transmitter this localization message routing, the electronic station sign after receiving this localization information, (obtains in advance this localization information with own static state positional information by the GPS receiver) carries on the contrast, if its differential value (for instance public transportation enters the station in the stipulation scope time), gives the public transportation by the electronic station sign returns specific instruction newspaper station stand information, after the public transportation receives this specific instruction stand order, reads in the specific broadcast address by the DSP processor through and the mouth to the speech chip, the speech chipThrough this broadcast address, after the filter, broadcasts this specific pronunciation information by the speaker, has like this realized public transportation’s automatic newspaper station function.
1.1 vehicles carry the equipment
The so-called vehicle carries the equipment is also refers to installs on public transport’s equipment, it is in the mass transit information service system the important constituent. Must realize the function which the mass transit information system has, namely has the GPS satellite positioning information receive, the public transportation automatic newspaper to stand as well as with electronic station sign functions and so on two-way communication, speaking of the hardware constitution, the vehicle carries the equipment to by the GPS receiving antenna, the GPS receiver, the communication controller, the automatic newspaper station equipment as well as the wireless receiver transmitter and so on several important parts is composed.
(1) GPS receiver
The public transportation vehicle carries in equipment’s GPS receiver is mainly uses for to gain public transportation’s localization information, it can receive the localization material which the satellite sends out, and may to the GPS signal which receives carry on the transformation, the enlargement and processing, with the aim of surveying the GPS signal from the satellite to receiver antenna’s propagation time, interprets guidance telegram text which the GPS satellite transmits, real-time computation information [10] and so on observation station three dimensional position, three dimensional speed and time. The vehicle carries the GPS receiver to be possible to select may supply the re-development Garmin (wise) GPS25 OEM, it has the parallel 12 channels, can simultaneously track 12 GPS navigation satellite, the sensitivity is high, the localization speed is quick, the power loss is low, the performance-to-price ratio is high, some 2 compatible RS-232 duplex channel, can simultaneously transmit the standard NMEA-0183 data, its non-difference pointing accuracy in 10 meters, the power loss is small, the data turnover rate is quick, may amount to for 1/second.
When in processes the data which the GPS receiver receives, generally through to the frame head’s judgment determined first whether is ” $GPRMC ” the frame structure, then carries on the data again to this frame extraction processing. If the situation is special, needs from other gain data, the processing method with it also to be completely similar. Because in frame various data segment by comma division, therefore when processes the buffer data generally is through searches for the ASCII code ” $ ” to judge whether is the frame head, in carries on the recognition after the frame head’s category the one who through to experiences the comma integer the counting to judge again is processing presently is which one kind of localization guidance parameter, and makes corresponding processing.
The processing process is mainly divided four steps to carry on: Must first determine current transmits the data byte is whether legitimate, namely this data byte whether is in the data packet data which belongs to us to need; Then the determination transmits data byte in this data packet position; Then to the data byte which gathers carries on the preservation; Finally when the entire data packet transmission ended, handed over carries on computation processing by the disposal procedure part.
(2) communication controller
The communication controller uses DSP processing chip TMS320VC5402, it is a section of performance-to-price ratio extremely high fixed point DSP chip which TI Corporation promotes. Its performance characteristic is as follows: The operation speed may reach 100MIPS; Has the advanced multi-bus structure, three 16 bit data memory main line and a program memory main line; 40 arithmetic logic unit (ALU), including a 40 doliform shifter and two 40 accumulators; A 17×17 multiplier and 40 special-purpose accumulators, allow 16 belts/not to have the mark multiplication; The conformity Viterbi accelerator, uses in enhancing Viterbi to arrange the decoding the speed; Monocycle standardization and index decoding; 8 auxiliary registers and a software stack, permission use field most advanced fixed point DSP C language compiler; The data/procedure addressing space is 1M×16bit, built-in 4K×16bit ROM and 16k×16bit RAM; Built-in programmable waiting status generator, phase-locked loop (PLL) clock producer, two multichannel cushion serial port, with exterior processor correspondence 8 bit parallel HPI mouth, two 16 timers as well as 6 channel DMA controller, and low power loss. Compare with C54X series’s other chips, C5402 has characteristics and so on high performance, low power loss and low price. It uses 6 levels of assembly lines, when and RPT (redundant instruction), some multi-cycle’s instruction turned the monocycle instruction; Chip internal RAM and ROM may act according to PMST register’s OVLY and the DROM position nimble establishment. These are advantageous to the algorithm optimization.
C5402 uses 3.3V and the 1.8V power source power supply, I/O uses the 3.3V power source power supply, the chip nucleus uses the 1.8V power source power supply.
(3) wireless receiver transmitter
The wireless receiver transmitter carries an equipment’s part as the vehicle, is the public transportation and the electronic station sign correspondence wireless bridge. It mainly completes the instruction order which the receive electron station sign transmits, carries on processing through the communication controller to realize the automatic newspaper station function. Because only needs stands in the newspaper in the scope realizes between the station sign and public transportation’s wireless communication, therefore uses the wireless receiver transmitter which the general wireless receiving and dispatching module constitutes then, for instance here may use Motorola’s two model of chip MC33493 launch chip as well as the MC33594 receive chip then, specifically wireless communication here does not aggravate an introduction.
1.2 electronic station signs
The electronic station sign mainly completes with the public transportation between the information exchange, in addition may complete to the stand information demonstration function, therefore electronic station sign system mainly by wireless receiver transmitter, communication controller as well as LED display system constitution, the communication controller also uses DSP processing chip TMS320VC5402. Because electronic station sign after receiving the localization information which the public transportation sends back, must judge the public transportation whether already to arrive at the newspaper station scope, the concrete treating processes are as follows:
Supposes the electronic station sign the positional information is: The longitude, the latitude is; The public transportation current positional information is: The longitude, the latitude is, then the current public transportation and the electronic station sign’s distance (differential value is very highly small, may ignore) is: 
(1-1)
The TMS320VC5402 operating speed is quick, very simple can obtain the station sign and public transportation absolute distance at this moment through the programming, when satisfies the newspaper station scope by the electronic station sign transmission corresponding newspaper station order, such public transportation after receiving the newspaper station order can realize the automatic newspaper to stand.
2. in the automatic newspaper station system is related the hardware circuit composition
2.1 serial interface electric circuit composition
In the automatic newspaper station system between the GPS receiver, the wireless receiver transmitter and the DSP processor’s correspondence is realizes through the serial port. In the system uses TMS320VC5402 does not have the standard RS232 connection, but may use its XF, BIO, INT0 and the timer realizes a most Jan the RS232 connection, thus achieves the serial communication the goal, here has enumerated between the DSP processing chip and the GPS receiver’s serial communication electric circuit, as shown in Figure 2.
2.2 pronunciation newspaper station pronunciation hardware circuit composition
In the pronunciation newspaper station pronunciation hardware circuit may use the 1SD4004 speech synthesis chip which 1SD Corporation produces, this component has the acoustic fidelity nature, the easy to operate, monolithic depositing, to record, the low power loss, the anti-power failure repeatedly and so on many special energy. In the practical application, the recording part will include the content to save in advance to the speech chip, and assigns a specific broadcast address, when needs to report stands, only needs to read should broadcast the first address, reports the station information automatically to broadcast immediately by the speech chip through the speaker, realizes the newspaper station. Uses the 1SD4004 speech chip in here to design the automobile newspaper to stand, its peripheral circuit and simple, like the chart shows:
May see between TMS320VC5402 and the ISD4004 line connection from the chart are few, the circuit structure is quite simple. In TMS320VC5402 D1 meets ISD4004 serial input pin MOSI, from this pin read-in playback address; The D2 data line connects ISD4004 to select patches or strips of land as worth saving for seed pin /SS, controls ISD4004 whether to select; D3 and D4 meet ISD4004 separately serial clock pin SCLK and interrupt pin /INT. When needs to report stands, only needs to read should broadcast the first address, sends in turn immediately by the DSP in D1 base pin under clock’s control this address the speech chip, broadcasts automatically through the filter by the speaker, realizes the real-time newspaper station.
3. the system function software realizes
On after component electricity, first completes the procedure the initialization, afterward enters the examination to receive the stand command phase. If the public transportation receives instructs the stand order, then transfers carries out the data reduction program which this stand aims. Each stand order represents a corresponding station, through the judgment current station number, and obtains depositing take this station number as the basis should the station playback content first address, then the transfer playback subroutine, the read-in saves in advance the home station playback content first address, starts the playback. After each playback finished, the ISD4004 interrupt pin (25 feet) will deliver a low level signal automatically. In hardware design, this pin and DSP in chip D1 connection, will therefore cause one time to interrupt, may carry on the stand in the interrupt subroutine the demonstration. In addition, if obtains each corner in advance the static GPS localization information, then after the public transportation receives the localization information, two localization information carries on the contrast, if its differential value also in the prescribed limit, this time may cause procedure turn to carry out the special language playback (for example “corner please to note” and so on sentences).
Concrete program flow chart as shown in Figure 4. The public transportation while arrives at which every one stands, the electronic station sign can with receive oneself positional information vehicle’s localization information contrast, when its differential value in decides in the scope, this time the electronic station sign will transmit the stand newspaper station order to the public transportation. After the public transportation receives the concrete newspaper station order, through judges the stand number to be possible to obtain the corresponding stand playback content first address, the playback content’s address which obtains delivers in ISD4004, namely may complete the playback. In the public transportation completes stands after the home station automatic newspaper, immediately cuts to the next station newspaper station order inquiry, works in turn, may realize to the entire strip line’s newspaper station function.
4. conclusion
This article uses the DSP processing chip has and the important application in the public transportation automatic newspaper station system, not only it plays the control the role, docks the GPS localization information which receives to carry on processing more importantly, the production distance information, is the system realizes the automatic newspaper station function key to be. In addition, because the DSP chip is extremely quick to data processing’s speed, unifies the GPS pointing accuracy the enhancement, enables whole set system to obtain very good manifestation in the practical application, enormous convenience public transportation passenger.
