Design of voice guide terminal based on RFID and speech synthesis technology

introduction

Some large museums and scenic spots in China have adopted some voice guides to provide tourists with various explanations and guides, which greatly facilitates tourists' understanding of the history and culture of museums and scenic spots. However, traditional voice guides have relatively simple functions, high power consumption, high cost, and complex data updates. Tourists need to manually enter codes to get the corresponding playback information, which limits the further promotion and use of voice guides. This design combines RFID radio frequency identification technology and TTS speech synthesis technology to propose a voice guide that can automatically identify the object of interpretation, and combines USB storage technology to achieve timely update of various guide information.

1 Analysis of RFID technology, TTS technology and terminal functions

RFID (Radio Frequency Identification), commonly known as electronic tags, is a contactless automatic identification technology. It automatically identifies the target object and obtains relevant data through radio frequency signals. The identification work does not require human intervention and can work in various harsh environments. RFID technology can identify high-speed moving objects and can identify multiple tags at the same time, and the operation is quick and convenient. The most basic RFID system consists of three parts: tags, which are composed of coupling elements and chips. Each tag has a unique electronic code and is attached to the object to identify the target object; readers, devices that read (and sometimes write) tag information, can be designed as handheld or fixed; antennas, which transmit radio frequency signals between tags and readers.

TTS (Text To Speech) technology solves the problem of how to convert text information into sound information, thereby changing seeing into hearing, making the way people obtain information more abundant and natural. Speech synthesis technology is one of the key technologies for realizing human-computer voice communication, involving knowledge of multiple disciplines such as acoustics, linguistics, digital signal processing, computer science, etc., and is a cutting-edge technology in the field of Chinese information processing.

As a portable terminal, the entire design of the voice guide terminal must meet the low power consumption requirement to ensure that it has enough energy to work reliably. At the same time, through the analysis of the voice guides currently used in the market, the voice guide terminal to be implemented in this design mainly realizes the following basic functions: automatic recognition of target objects; active playback of guide information; USB information update; tour route display; service information query.

2. Hardware Principle Design of Voice Guide Terminal

The basic principle block diagram of the voice guide terminal is shown in Figure 1. The RFID reader circuit sends the acquired tag information to the microcontroller. The microcontroller reads the corresponding text information from the data storage according to the tag information and sends it to the TTS speech synthesis circuit through the serial port. The TTS speech synthesis circuit converts the text information into voice information, which is then amplified by the audio amplifier circuit and sent to the built-in speaker or external headphones. At the same time, the LCD display screen displays the current tour route according to the tag information. In addition, some service information can be queried through the human-machine interface.

2.1 EM4095 RFID reader circuit

EM4095 is an RFID base station reader/writer chip with a carrier operating frequency of 100 to 150 kHz. It can operate tags such as EM400X, EM4050, and EM4150. When the working circuit shown in Figure 2 is used, its operating frequency is determined by the following relationship:

In practical applications, the capacitor in the above formula is selected as a ceramic capacitor, and the value of the inductor L1 is appropriately adjusted according to the actual test conditions to ensure that the operating frequency is 125 kHz.

2.2 XF-S3011 speech synthesis and audio amplifier circuit

The XF-S3011 chip is a Chinese speech synthesis chip developed by iFlytek Information Technology Co., Ltd. It fully integrates the complete speech synthesis system into a single processor, and receives and synthesizes any text through the serial port. The serial port baud rate is 9600 bps, and the current working status (Busy/Ready) of the speech chip is indicated through the RAD port. Since the audio signal power output by the XF-S3011 chip is relatively small, in order to make the audio signal have enough power to drive the speaker, it needs to be amplified by the LM4871 circuit, and the amplification gain can be adjusted by the resistor R. Figures 3 and 4 are the peripheral circuit design diagrams of the XF-S3011 chip and the LM4871 chip.

2.3 Microcontroller and interface circuit

The microcontroller uses LPC2146, which has 32 KB+8 KB and 256 KB embedded high-speed Flash memory, built-in USB 2.0 full-speed device, UART, SPI, SSP, I2C serial communication interface, ultra-small LQFP64 package, low power consumption. In order to connect with LCD 160×128, large-capacity data storage (SST39VF080) and keyboard, this design uses 74L574 and 74L245 to expand the I/O port.

In addition to ISP programming, the serial port 1 of LPC2146 can also be used to set system working parameters. At the same time, during the program debugging process, some status points can be set to facilitate code debugging and testing. The host computer management software communicates with LPC2146 through the USB port. LPC2146 saves the navigation information sent by the host computer into a large-capacity program memory in a certain format, which can facilitate timely data updates.

2.4 Power Management Module

For the voice guide terminal, multiple power supplies are required internally. Therefore, how to reasonably design the power management module has a very important impact on the stable operation of the terminal and the control of power consumption. This design uses the MAXl677 power management chip to convert the power provided by the lithium battery into two paths, one for the EL backlight driver, and the other outputs 3.3 V voltage for LPC2146 and other peripheral chips. The 3.3 V voltage is then converted to 1.8 V voltage by the SPX5205/1.8 V chip and provided to the LPC2146 core.

3 Application Software Design

In order to reduce system resource overhead and take into account the terminal function requirements, the software design uses the ARTX operating system that comes with Keil C51. This operating system is simple to use, occupies few resources, and is suitable for applications where real-time requirements are not too high. The terminal software program framework is shown in Figure 5, which mainly includes five parts: main control program, ARTX kernel program, user tasks, bottom-level driver, and configuration and settings. The basic process of software operation is:

① After power-on reset, the main control program runs, completes variable initialization, RAM allocation, task block initialization, ARTX initialization, and then enters the while loop;

②In the white loop, start task scheduling and switching, the task query beat is 10 ms, after completing a task, query the task with the highest priority in the task table and start executing;

③The external interrupt will start the corresponding interrupt handler, which will prompt certain tasks to be ready. The ready tasks will queue up and wait for execution according to priority.

Conclusion

The application of RFID technology in voice guide terminals solves the trouble of manually inputting identification information, realizes automatic information collection of identification objects, greatly simplifies routine operation procedures, and facilitates tourists to use; at the same time, combined with screen display, it provides tourists with accurate tour locations. Speech synthesis technology gets rid of the traditional recording storage mode, which reduces the requirements for terminal storage on the one hand, and realizes the rapid update of guide information on the other hand.