What Is a Graphic / Dot Matrix Display?
A graphic (dot matrix) display is a display type that divides the screen into an independent pixel grid, forming not only text but any shape, line and image.
Difference From a Character LCD
A character LCD only prints ready characters into fixed cells. In a graphic display each pixel is controlled separately; so custom fonts, icons, graphics and animation can be drawn.
Resolution
The display capacity is given in pixel count (e.g. 128×64). As resolution rises, finer detail is shown but more memory and processing are needed.
| Property | Character LCD | Graphic LCD |
|---|---|---|
| Unit | Character cell | Pixel |
| Flexibility | Text only | Shape + text |
| Processing load | Low | Higher |
Driver and Interface
Most graphic LCDs contain a controller chip (e.g. ST7920, ST7565) and are driven with an SPI or parallel interface. The image is written pixel by pixel into memory with the help of libraries.
Where Is It Used?
Measurement instruments, 3D-printer/CNC interfaces, gaming devices, portable-device menus and embedded systems that visualize data.
Framebuffer
Graphic displays usually hold all the pixels in a framebuffer; drawing is done in this memory first, then transferred to the screen. A 128×64 monochrome display takes about 1 KB; on low-memory microcontrollers this limit must be kept in mind.
Common Mistakes
- Wrong library: if a driver suited to the controller chip isn't used, the display won't work.
- Memory: the framebuffer may not fit at high resolution.
- Refresh rate: slow updating makes animation flicker.
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