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The traditional electronic tour guide system generally adopts the infrared wireless communication method, and it is easy for the tourists to receive the wrong scenic spot information and cause the inconvenience of the tourists.
RFID (Radio Frequency Identification Technology) is a non-contact automatic identification technology that automatically recognizes target objects and acquires relevant data through radio frequency signals. The identification work can be performed in various harsh environments without manual intervention, especially RFID technology and The combination of Internet of Things applications has made it a hot topic of current research. Therefore, the intelligent voice player combined with RFID technology has also become a development trend, which enables users to conveniently visit in the exhibition hall, understand exhibits, listen to various cultural relics, introduce attractions, etc., and realize automated intelligent digital management of museums and the like. .
The portable intelligent voice player designed in this paper can download the scenic spot information through communication with the PC through the USB interface. The RFID electronic tag is placed in the scenic spot to transmit the encoded information of the scenic spot. When the tourist enters the scenic spot, the portable intelligent voice player receives the corresponding scenic spot code. After the information, encode and play.
System overall design <br> According to the characteristics of RFID technology, the overall structural block diagram of RFID-based portable intelligent voice player is designed, as shown in Figure 1.
The design consists of three parts: RFID module; wireless signal transceiver module; intelligent voice playback control and decoding module. It mainly includes RFID electronic tags and readers, STC12LE5410AD MCU for master control, VS1003 audio decoding chip, large-capacity memory, USB communication interface, etc.
When the player is in the working state, after the tag signal is recognized by the RFID reader, the voice signal information and the tag information are transmitted to the portable voice device corresponding to the tag information through the transceiver system, and the voice segment stored in the portable voice device is read and played. voice. The effective working distance of the system is 3~5 m, and it can store at least 3~5 segments (3~5 min per segment) voice files (built-in Chinese, English, Japanese voice files), and the voice files can also be controlled by the user through the player. Play.
RFID module design RFID system works: After the user tag enters the magnetic field, if it receives a special RF signal from the reader, the energy obtained by the induced current can be sent out to the passive tag (Passive Tag) chip. The product address information in the product, or the active tag (active tag, Active Tag) actively sends a certain frequency information, and then the reader reads the information and decodes it, and then processes the data.
The basic model of the RFID system is shown in Figure 2. The space (non-contact) coupling of the RF signal is realized between the electronic tag and the reader through the coupling element. In the coupling channel, data exchange and energy transfer are realized according to the timing relationship.
The working range (sensing distance) of the RFID-based portable intelligent voice player should be controlled at 3 to 5 m. Because the distance between the booths in the exhibition hall is small, if the sensing distance is too far, it is easy to cause interference between the signals. The voice clip has already been played, so the sensing distance is no more than 10m.
The electronic backscatter coupling method has a range of 3 to 10 m, which is in line with the sensing distance requirement of the portable intelligent voice player. At the same time, the passive electronic tag is more cost-effective than the active electronic tag, and the tag does not need to be powered by the built-in power supply, and is easy to be used. Portable and environmentally friendly, RFID-based portable smart voice players are more suitable for passive electronic tags that use electronic backscatter coupling.
Wireless signal transceiving module design <br> The wireless signal transceiving system works as follows: the wireless signal transceiving system receives the signal recognized by the RFID system reader, and the transmitting part transmits the signal; the wireless signal transceiving system receiving device receives the signal and transmits the signal Into a portable voice device.
The wireless signal transceiving system is composed of two parts: the wireless signal transmitting part of the RFID system part, which is divided into an encoding module and a signal transmitting module (including an antenna); a wireless signal receiving part of the portable voice device part, which is divided into signal receiving parts. Module (with antenna) and decoding module.
The information format of the wireless signal transmission and reception information transmission should include two parts: the address information is used by the portable intelligent voice player to identify the information source of the wireless signal of the receiving radio frequency identification system; the voice file number information is used for the portable intelligent voice player to recognize the voice file, Select a voice file to play. The format of the information sent is shown in Figure 3.
The transmitted information uses an 8-bit address code and a 4-digit information code. When the address is set, there are three states (floating, positive power, and ground), that is, the address code has a total of 38, that is, 6 561 sets of non-repeating coding modes. The information source address of the wireless signal can be effectively transmitted, and the transmission error or the repeated address information caused by the repetition of the address information can be avoided, so that the information cannot be recognized or the error of the incorrect information is recognized.
Intelligent voice playback control and decoding module design <br> Portable intelligent voice player is mainly composed of Micro Control Unit, audio decoder, storage device, PC communication port, audio DAC and power amplifier, display interface and control keys. The microcontroller and audio decoder are the core of the whole system.
The workflow of the portable intelligent voice player is shown in Figure 4.
First, the wireless signal receiving portion of the portable intelligent voice player receives the wireless signal, recognizes the voice signal stored by the player and plays it, and then decodes the signal by the audio decoding chip, and the audio is converted by the digital-to-analog converter. The digital signal is converted to an analog signal amplified output.
The entire control program of the portable intelligent voice player is completed by the operation of the single-chip microcomputer, and controls the operation of each part of the player (reading the voice signal from the storage device to the audio decoder for decoding, and completing the data exchange with the PC when connecting with the PC) , responding to the operation of the control button, displaying the operating state of the system, etc.; the audio decoder can directly perform the decoding operation of the audio signal in multiple formats; the storage device is an important part of the system, and is used for storing the audio signal pre-existing in the player. The data transmitted from the PC communication port can also be stored. The data in the memory is read by the single-chip microcomputer and sent to the audio decoder during playback; the PC communication port is a data exchange between the player and the PC, and the copy of the data in the memory is completed. , delete, copy and other operations; audio DAC is the conversion of digital audio signals into analog audio signals, convenient for use with headphones or amplifiers.
The STC12LE5410AD part of the single chip microcomputer is used for controlling the wireless signal in response to receiving and recognizing and reading the voice file information in the storage device, and playing the voice file decoded by the audio decoding chip, and controlling the LED display screen to display the file information (including the file name and the file length). , playback length, etc.), in addition, can also respond to button playback, pause, fast forward and volume adjustment on the player.
The STC12LE5410AD family of microcontrollers is a single clock/machine cycle compatible 8051 core microcontroller. The STC12LE5410AD features the following: Enhanced 1T Pipeline Reduced Instruction Set Structure 8051 CPU; user application space 12 KB, 10 KB, 8 KB, 6 KB, 4 KB, 2 KB; on-chip 512 B RAM; general purpose I/O port (27 /23), after reset to quasi-bidirectional port, weak pull-up (common 8051 traditional I / O port); can be set to four modes: quasi-bidirectional weak pull-up, push-pull strong pull-up, only input high resistance Open-drain I/O port drive capability can reach 20 mA, but the entire chip can not exceed 55 mA; ISP (programmable in the system), IAP (programmable in the application), no special programmer can be used through the serial port ( P3.0/P3.1) directly download the user program and complete one piece in a few seconds; internally integrate the MAX810 dedicated reset circuit (when the external crystal is below 20 MHz, the external reset circuit can be saved); clock source: external high-precision crystal clock, internal When downloading the user program, the R/C oscillator user can choose whether to use the internal R/C oscillator or the external crystal clock; the internal R/C oscillator frequency is 5.2~6.8 MHz at normal temperature, and the accuracy is not high. When you choose, you can choose to use the internal clock, but because of the temperature drift, you should It is is 4 ~ 8 MHz; of 2 16-bit timers, counters.
When the MCU partially acquires the file information of the voice signal in the wireless signal, the corresponding voice signal is read, the voice file is decoded by the audio decoding chip, and then the decoded audio file is played by the earphone or other audio device by the single chip microcomputer.
The VS1003 is an MP3, WMA, MIDI audio decoder and ADPCM encoder. The VS1003 receives the input bit stream through a serial interface. It can be used as a slave to the system. The input bit stream is decoded and then passed through a digital volume controller to an 18-bit oversampling multi-bit, controlled via a serial bus. decoder. The VS1003 features the following: Can decode MPEG 1 and MPEG 2 Audio Layer III (CBR+VBR+ABR), WMA 4.0/4.1/7/8/9, 5 to 384 Kb/s all stream files, WAV (PCM) +IMAAD-PCM) format file; single clock operation 12.13 MHz; internal PLL phase-locked loop clock multiplier; contains high-performance on-chip stereo digital-to-analog converter; analog, digital, I/O separate power supply; 5.5 KB of on-chip RAM for code and data preparation.
The storage medium of the player is an SD card. The SD card is widely used in mobile storage devices, and has a variety of capacities, which is convenient for the user to arbitrarily change the voice file in the storage medium, and the cost is low; using USB to communicate with the PC, It is convenient for the user to guide the voice file to the player; the display part adopts an LED display screen for the user to understand the brief information of the exhibit through the display screen.
The schematic diagram of the circuit design of the portable intelligent voice player is shown in Figure 5.
Conclusion <br> The RFID-based portable intelligent voice player designed and implemented in this paper uses STC12LE5410AD as the main control chip, and uses VS1003 audio decoding chip. Combined with RFID technology, it can realize wireless data communication in all directions such as museum exhibition hall. The system not only has the function of electronic tour guide system, but also can be used for traffic management and parking lot management.
Design of Portable Intelligent Voice Player Based on RFID
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