The most complete dot matrix LCD display principle and method of use
The display principle of a dot matrix LCD is based on the binary system, where all data is represented using 0s and 1s. In digital circuits, different operations are performed on the LCD controller to generate various outputs. For English characters, which are limited in number, only 8 bits (one byte) are required. However, for Chinese characters, which exceed 6,000 commonly used characters, an internal code system was developed. This system uses two ASCII values that are rarely used to represent Chinese characters, while the lower 128 bits remain reserved for English characters, forming the English internal code.
Once the internal code of a Chinese character is obtained, it's just a set of numbers. To display these on the screen, fonts are used. Fonts are also sets of numbers, but they have a different meaning — they define the shape of characters. For example, the font for the letter 'A' is stored as a pattern of dots, as shown in Figure 1:
Figure 1: Font map for "A"
Similarly, the Chinese character “you†is represented in a dot matrix format, as shown in Figure 2:
Figure 2: Font map for "You"
The 12864 dot matrix LCD is a graphic display module composed of row and column drivers, along with a 128×64 full dot matrix liquid crystal display. It can show 8×4 or 16×16 Chinese characters. The structure is illustrated in the following image:
Before using the 12864 LCD, it's essential to understand its internal components and functions. These include the Instruction Register (IR), Data Register (DR), Busy Flag (BF), Display Flip-Flop (DFF), XY Address Counter, Display Data RAM (DDRAM), and Z Address Counter. Each component plays a specific role in controlling the display and managing data transfer.
The instruction system of the 12864 LCD is relatively simple, with only seven commands available. These include commands for turning the display on/off, setting the page, reading status, writing data, and more. Each command has a specific function and timing requirement to ensure proper operation of the display module.
To demonstrate the use of the 12864 LCD, a practical example is provided. This example involves displaying a specific layout on the screen, as shown in Figure 3:
Figure 3: Simulation display rendering
The hardware schematic and software flowchart are also included to guide the implementation. A sample program is provided, showing how to generate and display Chinese characters using a modulo tool. By entering the desired text and selecting the appropriate format, the corresponding dot matrix code is generated, which can then be embedded into the program to display the character on the screen.
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