STM32 Microcontroller Practical Guide to Graphical Display: In-depth LCD Driver, Graphics Library, and Touch Screen Implementation for Cool Human-Machine Interaction

# 1. Overview of STM32 Graphics Display**

STM32 microcontrollers are widely used in industrial control, consumer electronics, medical devices, and other fields, with graphics display functionality being one of their important applications. This chapter will provide an overview of STM32 graphics display technology, including the principles of graphics display, STM32's graphics display capabilities, and the applications of graphics display.

STM32 microcontrollers achieve graphics display through LCD (liquid crystal display). LCDs consist of liquid crystal materials, and the arrangement of liquid crystal molecules changes under the influence of an electric field, thereby achieving image display. STM32 microcontrollers drive LCDs via dedicated interfaces (such as FSMC, LTDC) to control the arrangement of liquid crystal molecules, realizing image display.

STM32 microcontrollers possess powerful graphics display capabilities, supporting various resolutions, color depths, and display modes. Moreover, STM32 provides a wealth of graphics libraries, such as STemWin, TouchGFX, etc., which offer abundant functions for graphics drawing, image loading, and touchscreen interaction, greatly simplifying the development work of graphics display.

# 2. LCD Drivers and Graphics Libraries**

**2.1 Principles of LCD Drivers**

**2.1.1 Structure and Operation of LCD**

A liquid crystal display (LCD) is a thin and flat display device that changes the transmittance of light by controlling the arrangement of liquid crystal molecules to display images. An LCD consists of the following main components:

- **Backlight:** Light-emitting diodes (LEDs) or cold cathode fluorescent lamps (CCFLs) provide the backlight required for display.
- **Polarizing Film:** Two layers of film, with their molecules arranged in a specific direction, control the polarization of light entering and leaving the LCD.
- **Liquid Crystal Layer:** A thin layer of liquid crystal molecules, whose arrangement can change to alter the transmittance.
- **Color Filter:** A thin film that decomposes white light into the primary colors red, green, and blue (RGB).
- **Thin Film Transistor (TFT):** Electronic switches that control the arrangement of liquid crystal molecules.

The operation of an LCD is as follows:

1. The backlight emits white light.
2. The polarizing film polarizes the white light in one direction.
3. The liquid crystal molecules in the liquid crystal layer align with the direction of the polarized light.
4. The liquid crystal layer allows polarized light to pass through.
5. The color filter decomposes white light into RGB primary colors.
6. TFT controls the arrangement of liquid crystal molecules to change the transmittance.
7. The light passing through forms an image.

**2.1.2 STM32's LCD Driver Interfaces**

STM32 microcontrollers provide various LCD driver interfaces, including:

- **Parallel Interface:** Communicates directly with the LCD using a data bus and control signals.
- **Serial Interface:** Communicates with the LCD using SPI, I2C, or other serial protocols.
- **Dedicated LCD Controller:** An integrated peripheral in the STM32 chip for driving the LCD.

**2.2 Introduction to Graphics Libraries**

**2.2.1 Concepts and Classification of Graphics Libraries**

A graphics library is a set of functions and data structures used for creating and displaying graphics in embedded systems. Graphics libraries can be classified into the following categories:

- **Low-Level Graphics Library:** Provides basic graphic drawing functions, such as drawing points, lines, and rectangles.
- **Mid-Level Graphics Library:** Provides advanced graphic drawing functions, such as image loading, text rendering, and animation.
- **High-Level Graphics Library:** Provides a complete graphical user interface (GUI) development framework, including windows, buttons, and menus.

**2.2.2 Commonly Used STM32 Graphics Libraries**

Commonly used STM32 graphics libraries include:

- **STemWin:** A commercial graphics library developed by STMicroelectronics, offering extensive graphic drawing, GUI development, and touchscreen support functions.
- **LittlevGL:** An open-source graphics library known for its compactness, efficiency, and ease of use.
- **uC/GUI:** A commercial graphics library that provides extensive graphic drawing, GUI development, and touchscreen support functions.

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