Chinese Character Input in 51 Single-Chip Microcomputer Display and Control System

For PC, inputting Chinese characters is very simple, but in some single-chip human-machine interface systems, real-time input of Chinese characters is very difficult, and most of them can only display Chinese characters with pre-selected font dot matrix. However, each 16×16 Chinese character dot matrix is ​​represented by 32 bytes. For occasions that require flexible use of a large number of Chinese characters, the program volume is too large and it is very difficult to implement. The following analyzes the structure of the Chinese character library, designs a practical Chinese pinyin input method, and gives the basic program of the LCD Chinese character display module.

1 Internal code representation of Chinese characters

Different operating systems have different internal codes for Chinese characters. For example, GB231280 Chinese character code is used on Apple OS, while GBK Chinese character code is used on Windows system. There are also Unicode code, GB180302000, Founder 748 code, etc. Since GB 231280 is the earliest (1980) "General Chinese Character Set and Its Interchange Standard Code" promulgated by the China National Bureau of Standards, all subsequent codes are compatible with GB2312. It contains 7,445 Chinese characters, letters, symbols, etc., including 6,763 Chinese characters, including 3,755 first-level Chinese characters and 3,008 second-level Chinese characters. It is the only Chinese code that is mandatory for use in mainland China and overseas regions that use simplified Chinese (such as Singapore, etc.), so it is also called the standard Chinese character library.

The dot matrix data of each Chinese character needs to occupy 32 B of memory, where the strokes are displayed is 1, and where there are no strokes is 0. Then the dot matrix data is converted into a dot matrix data form that can be displayed by the dot matrix LCD through the C51 language of the single-chip microcomputer.

2. Production of Chinese Character Library

This section discusses the specific method of burning a 16×16 dot matrix Song style Chinese character library into a 512 kB memory.

The memory chip used in this example is AM29C040, which is a 512 kB FLASH ROM produced by AMD. Readers can also use other products with a capacity of not less than 256 kB, but in the specific circuit design, attention should be paid to the pin definition and logical relationship, and the corresponding model should be selected when burning; UCDOS software has a file named HZK16DAT, which is a 16×16 national standard Chinese character dot matrix file. In this file, all Chinese characters in the national standard area code are stored in order from small to large according to the Chinese character area code. Each Chinese character occupies 32 B, and each area is 94 Chinese characters. Its size is 262 kB, which can all be written into AM29C040. In addition to storing all national standard Chinese characters, it can also store 8×16 ASCII code dot matrix data and Chinese character sentence encoding data, which is more convenient to use.

In actual operation, the production of a hardware Chinese character library is no different from the programming of an ordinary program memory. Note that when calling in the HZK16 file, it must be opened in binary mode. After successful programming and verification, the memory can be removed for use. In this way, a hardware Chinese character library is produced.

3 Design ideas

In this example, starting from the low-cost and low-power design concept, the Philips P89C51RD2 microcontroller is used as the core, and the input uses a 4×4 multiplexed keyboard, which can input numbers, letters or pinyin. The Chinese character library is stored in AMD's A M29C040 (512 k×8 b) FLASH, the LCD module DMF50174 (320×240), and the display controller SE D1335 is a liquid crystal display control chip produced by Japan's SEIKO EPSON. The chip select (control signal) of each chip is generated by 74 HC138 decoding.

The Chinese pinyin is input by keyboard, the single chip retrieves the area code, reads the Chinese character dot matrix design from FLASH, displays it on LCD, and uses the IAP function of P89C51RD2 to program online and change the user interface or interface function online.

4 Chinese character input

P89C51RD2 is a very excellent single-chip microcomputer released by Philips in 2001. This single-chip microcomputer is a derivative product based on the 8-bit 80C51 single-chip microcomputer. In addition to fully retaining the large framework of the 80C51 instruction system and hardware structure, it has carried out many aspects of strengthening, expansion and innovation. P89C51RD2 utilizes the original 16-bit addressing mechanism for external data and program memory, expands the on-chip RAM to 1 kB, and the on-chip FLASH EPROM to 64 kB. It has ISP (in-system programmable) and IAP (in-application programming), and has 6-clock and 12-clock modes. In the 6-clock mode, the external crystal oscillator is 0-20 MHz, and in the 12-clock mode, the external crystal oscillator can reach 0-33 MHz.

As a general application system, the Chinese characters in the first and second level character libraries are sufficient.