Abstract: Based on ISD single-chip voice recording and playback integrated circuit and large-capacity IC card, the design method of IC card electronic voice book is given. This electronic voice book has the characteristics of small size, light weight, low power consumption and low cost. Keywords: IC card voice recording and playback text conversion so-called "IC card electronic voice book", that is, reading the information in the IC card, and then converting it into sound information, to replace the existing electronic device of the book, can be inconvenient Visually read people (such as the elderly, blind or patients, etc.) use. At present, the capacity of IC cards sold in the domestic market can reach 500K bytes. For example, direct storage of voice signals (in 8K/sec sampling rate) can store about 62.5 seconds of direct voice information. Although the stored sound quality is better, it obviously cannot meet the requirements of the general book to borrow a large amount of information storage. The author stores the Chinese character's speech coding (custom), storing a Chinese character only takes 1.5 bytes (12 bits), then the 500K byte IC card can store no less than 333,000 Chinese characters, and can play nearly 30 consecutively. Hours are enough to meet practical requirements. The design scheme given in this paper uses AT89LV51 single-chip microcomputer as the microprocessor, with ISD4004 as voice support, and AT45D041 type IC card as the electronic book information storage carrier. The AT45D041 IC card is a large-capacity memory card (4M bit) introduced by ATMEL in the United States in recent years. It is the largest IC card that is easily available on the market. With the advancement of technology, when switching to other types of IC cards with larger capacity, this design scheme still applies as long as the communication method remains unchanged. Even if the method is changed, you only need to modify the design. The basic working process of the device is as follows: first, convert Chinese character text files (such as "Three Kingdoms") into voice code files and store them in the IC card (this work is done by PC); then, when the IC card electronic voice book works The CPU in the playback device reads the speech code from the IC card; finally, the CPU controls the ISD single-chip voice recording and playback circuit according to the code, and plays the corresponding voice. This design scheme is an economical and practical electronic language book basic design scheme. Although it is not as good as the voice direct storage scheme in terms of sound quality, it has the advantages of low cost, small size, low power consumption and long continuous playing time. 1 The hardware schematic diagram of the hardware design playback device is shown in Figure 1. Figure 1 IC card electronic voice book electrical schematic diagram This design has six buttons, respectively, "play" (BUTTON0), "fast forward" (BUTTON1), "slow forward" (BUTTON2), "fast retreat" (BUTTON3 ), "slow back" (BUTTON4) and "stop" (BUTTON5). In order to be able to resume playback from the last stop at the next boot, a data memory with power-down hold is required. The AT24C01A is used in this article. In order to minimize the size and weight of the playback device, the device uses only one AA type (ie, No. 5) battery, so a step-up switching type regulated power supply is required. This article uses the MAX856. In order to save battery consumption, the device should have the function of automatic power off. When the "Play" button is pressed, the MAX856 chip 1 pin will be raised to a high level and the device will be powered. After that, the microcontroller sends a high-level pulse to the MAX856 chip 1 pin every 16 seconds to allow the device to continue to be powered. When the timing time (60 minutes) expires, the device stops sending a high level pulse to the MAX856 chip, and the device automatically powers down. The main functions and technical parameters of the AT45D041 large-capacity IC memory card used in this design are as follows:
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(1) has a serial interface compatible with SPI;
(2) 4325376;
(3) Low power consumption, dynamic current is 15mA, static standby current is 20μA;
(4) The maximum clock frequency is 10MHz. Refer to the reference [1] for the pins and commands of the AT45D041 high-capacity IC memory card.
Pins 1 to 8 of IC_CARD correspond to pins 1 to 8 of the AT45D041; 9 and 10 are auxiliary contacts of the IC card holder for detecting whether the IC card has been inserted. The main functions and technical parameters of the ISD4004 voice chip used in this design are as follows:
(1) 16 minutes voice recording and playback, the minimum length is 200 ~ 400ms (this design uses 300ms);
(2) The maximum number of segments is 2,400;
(3) SPI interface mode. The main pin of the ISD4004 voice core sleep and the connection method with the MCU are described as follows: AUD OUT--output audio signal, in order to get a larger output, use the power amplifier LM386 to amplify and provide it to the earphone or speaker. SS--chip select, active low, high between two instructions. MOSI--serial input, the main controller should put data to the local end half a cycle before the rising edge of the serial clock. MIS0 - serial output. SCLK--Serial clock input, generated by the main controller, used to synchronize the data transfer between MOSI and MISO. The above four terminals are respectively connected to P1.7 to P1.4 of the single chip microcomputer. /INT--Interrupt, the local end is an open-drain output. When EOM or OVF is detected in any operation, the local end goes low and remains; RAC--row address clock, open-drain output, for storage management, connected to the P1.3 of the microcontroller. 2 Voice code file formation The ISD4004 voice chip stores sounds in segments, one for each segment, and each tone is 300ms. However, it should be noted that many words have the same pronunciation (such as ye3: also, smelting, wild); while some pronunciations have no Chinese characters (such as: wai2, sai3, ka2, etc.). For each different sound, there are 5 basic sounds (ie, Yinping 1, Yangping 2, Shangsheng 3, Going 4 and Soft 5). As long as there is a Chinese character corresponding to it (the same pronunciation is only one), then a code is given, so that all the voice codes can be obtained. There are a total of 1311 pronunciations of Chinese characters. In design, all the different sounds are arranged in English byte and vocal order. There are 1337 (1311 Chinese characters + 26 English letters) voice codes, which is 1337 voices. With 1.5 bytes to store a voice code (that is, 1 Chinese character pronunciation), the 4M-bit IC card can store nearly 349,500 Chinese character voices. After the voice code is determined, 1337 voices can be written in the order of the voice code in the ISD4004 voice chip. First, according to GB2312-80, the conversion table of internal code and voice code of two-level Chinese characters is given, see Table 1. For each word in a given text file, you only need to find out its location code, then you can get the pinyin code by looking up the table, and finally write the pinyin code to the large-capacity IC card. For punctuation, treat it as a pause (no sound). It is worth noting that some Chinese characters (such as: and, he2, he4, huo2, huo4, hu2) have multiple pronunciations, and there will be multiple voice codes corresponding to these Chinese characters. If you want to convert to which voice code, you need to refer to the previous Chinese character or the latter Chinese character of the Chinese character. When it is still uncertain, the sound with the highest probability of occurrence (such as sum and he2) should be taken. Table 1 Conversion table of regional code and pinyin code (fragment) Location code Chinese pronunciation pinyin code (hexadecimal) Pinyin sequence number (decimal) ... ... ... ... ... 1712 Blast bao4 01F 31 1713 Cup bei1 020 32 1714 Monument bei1 020 32 1715 悲bei1 020 32 1716 å‘bei1 020 32 1717 北bei3 021 33 ... ... ... ... ... ... VB program to convert the text file in the computer to the voice code of the text, and write it into the IC card, thus forming an "electronic Voice book". Different IC cards are loaded with different contents, ie different "books". Note that the contents of the IC card can be rewritten. After a book has been heard, you can also go to a special service point and exchange a new "book" to listen to. According to the scheme given in this paper, the volume of the IC card electronic voice book insertion and loading is about 120mm%26; #215; 80mm%26; #215; 14mm. The phonetic pronunciation of the device is slightly stiff. If the intelligent processing algorithm can be further introduced to make the connection between the pronunciations of Chinese characters softer, the sounding effect will be improved.
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