The abstract introduced that one kind and dodges the MP3 public transportation newspaper which based on at89C51SNDlC monolithic integrated circuit saves realizes to stand, may realizes the high quality pronunciation information broadcast through the keyboard and the broadcast listing file, simultaneously uses the LED lattice demonstration broadcast the content, the newspaper stands may take the superior plate to replace the pronunciation document conveniently, is advantageous for the vehicle to carry the advertizing info the replacement.
The key word newspaper stands MP3 FATl6 filing system AT89C51SNDlC to dodge saves the LED lattice demonstration
Along with the urban fast development, the public transportation line is often making the adjustment, the station name also carries on the change along with it, moreover the vehicle carries the advertisement also more and more to be valued business’s, therefore a section can replace the pronunciation information, broadcast the high grade pronunciation information the automobile newspaper to stand appears more and more important conveniently. The traditional automobile newspaper stands uses the special-purpose speech synthesis chip to make. Speech synthesis chip information capacity, pronunciation acoustic fidelity limit, and the replacement information needs the specialized equipment and the public figure, thus causes to develop one kind of new automobile newspaper to stand appears the great importance. This article designs the newspaper stands may replace the broadcast content very conveniently, and may broadcast the high quality music.
1 newspaper stands the function
This newspaper station appliance has following function:
◇ may take the superior plate and the computer connection. The user may download the newspaper stands the broadcast content voluntarily, may also change the broadcast content conveniently.
◇ may the document which must broadcast through the edition broadcast listing file change.
◇ has 16 16×16 lattice Chinese characters, when the pronunciation broadcast may simultaneously use the Chinese character to prompt the broadcast content.
◇ broadcast high quality music, without newspaper station broadcast when may take the MP3 player, improves the public transportation grade of service.
2 system principle of work
This system uses at89C51SNDlC monolithic integrated circuit (interior to integrate the MP3 decoder) to take master control CPU and to decode the MP3 data, realizes to the newspaper station information broadcast, the lattice character display, the file memory as well as serves as when the superior plate function USB and PC machine on-line control. The system realizes the filing system using FATl6 on K9F1208, forms Windows to be possible to distinguish the visit the 64MB addressing region. Unifies the USB controller, the system may take the superior plate to use under Windows, thus realizes under Windows to the document management as well as the data storage function. The system has established a named SCHEDULE.LST listing file using the FATl6 filing system on K9F1208. This listing file’s different ranks took under the root directory the different MP3 document name, keyboard’s different pressed key have corresponded the listing file not to travel together the MP3 document name; When has a pressed key presses down, the procedure finds the MP3 document which in the listing file ought to do to correspond to carry on the broadcast. Like this through the procedure hypothesis, the public transportation may realize the MP3 form sound signal newspaper through the keyboard to stand as well as each kind of information broadcast. The listing file when the system to dodges saves the initialization produces, the system while to dodges saves carries on the formatting to produce this named sCHEDULE.LST the listing file. This listing file may open under Windows using the memorandum, edits the MP3 name which must broadcast. Broadcast newspaper station information at the same time through 16 16×16 LED lattice demonstration corresponding broadcast content. System diagram as shown in Figure 1.
3 parts of electric circuits
AT89C51SNDlC is one section which Atmel Corporation promotes integrates the MP3 hardware decoder and USB the revl.1 controller’s monolithic integrated circuit. It based on 8 C51 the MCU nucleus (highest clock rate is 20 MHz), built-in 2304 byte RAM and 64KB the Flash procedure space, has the 4KB guidance to dodge saves, provides surpasses 44 available general I/O mouths and many kinds of connections. And the very convenient design is the keyboard mouth which and the I2S form audio frequency connection 4 may interrupt. 4 may interrupt the keyboard mouth may compose 4×4 the keyboard matrix, but the I2S connection simplified the system circuit. What this design’s DAC uses is UDAl330. UDAl330 is a section of internal integration earphone operational amplifier which Philips Corporation promotes, has I2S connection DAC. Uses UDAl330 to be possible to further simplify the system circuit, and provides the L3 pattern and the static control two control modes, highest may provide 20 high quality sounds, is one kind of more ideal choice.
System schematic diagram as shown in Figure 2.
3.1 pronunciation processing part
At89C51SNDlC chip internal demoding circuit supports MEPG the I/II sound form third form the hard decoding, may process 48 kHz, 44.1kHz, 32 kHz, 24 kHz, 22.05kHz and 16 kHz the sampling frequency MP3 tonic train signaling, supports 31 levels of low, middle and high balanced controls and about the sound track independent volume control, the acoustic fidelity effect aspect obvious good in the speech synthesis chip.
In MP3 file memory Yu Shancun K9F1208. When carries on the newspaper station information broadcast, MCU pressed key which and presses according to the system current condition, according to the procedure hypothesis the MP3 filename which the search should broadcast from listing file SCHEDULE.IST. After the search, opens this document, examines this document MP3 data each, and examined a frame institute brings information whether with this consistency. If discovers the entire mistake in the tolerance interval, then recognized that the document may broadcast. MCU the control is realizes to the decoder through 9 with the MP3 decoder related special function register. When in input buffer already some complete frame, the decoder can start to broadcast. The decoder through MP3 in decoding condition register MP3STA and MP33TAl MPREQ, MPFREQ, the MPBREQ position realizes to the MP3 input block management handshake signal. When broadcast, MCU takes out the MP3 data frame from the MP3 document to send in the MP3DAT register. When the decoder needs the data, through the handshake signal, and initiates the corresponding interrupt, informs MCU to MP3DAT in the data-. The decoder also supports functions and so on CRC verification, frame synchronization wrong verification, here no longer gives unnecessary detail.
With the UDAl330 connection, at89C51SND1C I2S connection pin receives the UDAl330 correspondence separately on the pin. In order to enhance the tonic train signaling acoustic fidelity, UDAl330 uses the L3 pattern, the APPSEL earth. Under this pattern, APPL0 takes the test pin, APPL1 takes the L3 pattern the clock, APPL2 takes the L3 mode control, APPL3 takes the L3 pattern the data feeds, they with AT89C5lSNDlC P4.7, P4.4, P4.5, P4.O are separately connected.
The newspaper stands does not need to record the function, therefore the MIC electric circuit does not need to turn on the MP3 electric circuit. The MIC electric circuit’s tonic train signaling takes the automobile power amplifier another group input turning on, as shown in Figure 3.
3.2 superior function parts
This function involves on K9F1208 FATl6 filing system’s realization with manages, as well as USB from machine and main engine’s between correspondence. K9F1208 is a section of 64 MB Flash chip which Tristar Corporation promotes, the chip saves the region to divide into 4096 blocks, each block divides 32 pages, each page has 512 KB 16 bytes. Flash reads/writes has the following characteristic: Must carry on the read-write take the page as the unit, before writing, must clean the original content first; The cleaning operation must carry on to Block, namely one time cleans Block at least the content. Therefore FATl6 realization, may a page which leaves Flash decide as 1 sector, (64 sectors) decides as one bunch its 2 blocks. Thus, a bunch of capacity just is 512 bytes ×64=32KB, satisfies FATl6 to the bunch of size request. When FATl6 assignment space, its logical block address (LBA) and the Flash actual physical address’s transformation may carry on according to the below formula:
F1ash block address = logic block address /0×20
Flash page address = logic block address %0×20
According to such structure and the FATl6 request, realizes DBR, FAT, DIR and the DATA four areas on K9F1208, then realizes in the superior plate’s floppy disk management function. In at89C5lSND1C chip the integration has the USB controller, because Mass the Storage agreement and the vertex disposition, the enumeration, the course of communications are more complex, here no longer gives unnecessary detail, the hardware connection invites the reference diagram 2.
3.3 display circuits
As shown in Figure 4, the display circuit by IDT7132, AT89C5l, 74LSl54, 74HC573 as well as 1 16×256 LED lattice screen constitutes. IDT7132 is a piece of capacity is 32 KB pair of mouth RAM, because 16×256 the LED lattice screen demonstrated that the buffer altogether needs 512 byte storage spaces, the electric circuit uses it and saves the Chinese character displayed information with at89C5lSNDlC connection. 16×256 the LED lattice screen may demonstrate that 16 16×16 lattice Chinese characters, the display monitor divides 32 pages, each page divides into 16 lines. This design uses two piece of 4-16 decoder 74LS154 to combine 5-32 decoders, takes the page decoder; Uses piece of 74LSl54 to take the good decoder. Each page corresponds 74HC573, uses in locking debit and credit page some line of demonstrations the content; 32 74HC573 may lock saves 16×256 LED lattice screen line of contents, the display monitor by 7407 actuates. AT89C5l from pair of mouth RAM stipulated that the region takes out the demonstration content, the control page decoder sends in separately the data in each page of current lines, then controls the good decoder to line feed, so circulates forms the dynamic demonstration. The display circuit takes the ~ independent module use, when the newspaper stands the displayed information, only need want the Chinese character matrix which demonstrated to send in the pair of mouth RAM correspondence the memory region.
Conclusion
Along with MP3 player hardware cost’s reduction, the MP3 newspaper stands the performance and the cost advantage is getting more and more obvious, has the broad application prospect; And MP3 newspaper peace may replace the broadcast information conveniently, has the high use value and promotes the value.
