LED Display Screen

Updated: 6/28/2025 Words: 0 words Reading time: 0 minutes

In the previous section, we learned how to display a line of text on an LED dot matrix panel. In this section, we will learn how to display more content using an LED display screen.

Pixels and Resolution

To understand how a screen works, you first need to understand the concept of pixels. A pixel is the basic building block of an image on a screen. Any image is actually composed of countless pixels.

Under the backlight of the display, each pixel has a specific color value, usually combined from Red, Green, and Blue (RGB) values. When each pixel displays the corresponding color, a complete image is formed.

And what we commonly know as resolution refers to the number of pixels. For screens of the same size, the smaller the individual pixel, the more total pixels, the higher the resolution, and the clearer and sharper the displayed image.

Refresh Rate

Refresh rate, often referred to as "frame rate" or "refresh frequency," is an important parameter for various display technologies, including monitors, televisions, and digital screens. It defines how many times per second the image on the screen is redrawn or refreshed.

Refresh rate is measured in Hertz (Hz) and indicates how many times per second a display updates its content. For example, a 60Hz refresh rate means the display updates the image 60 times per second. Refresh rate has a significant impact on the smoothness of animation in videos, animations, and games. Higher refresh rates can make these visual effects appear smoother and more vivid.

In the past, the most common refresh rate for displays was 60Hz, determined by the frequency of AC power systems. However, modern displays typically support higher refresh rates, such as 120Hz, 144Hz, 240Hz, and even 360Hz.

High refresh rates can significantly reduce motion blur, making fast-moving objects on the screen appear clearer and gaming experiences smoother. But high refresh rates also require support from content and driving hardware. For example, to experience 120Hz gaming, you need a controller or computer capable of producing 120 frames per second. Moreover, most movies and TV shows are traditionally filmed at 24fps, which looks very smooth on a 60Hz display due to 3:2 pulldown technology, but may not fully utilize higher refresh rates.

LED Display vs. LCD Display

The main difference between these two types of displays lies in their backlighting. LED screens use light-emitting diodes as backlights, while LCDs use fluorescent backlights. Compared to traditional LCD displays, LED displays offer numerous advantages.

Firstly, each pixel on an LED display is independent, so it doesn't need to light up the entire backlight layer once turned on, unlike LCD screens, which implicitly saves energy consumption.

Additionally, precisely because each pixel on an LED display emits light independently, it can achieve nearly infinite contrast. Contrast refers to the ratio of brightness between black and white in an image. A higher contrast image appears richer in color. LED screens can directly turn off the backlight of corresponding pixels to improve contrast, thereby enhancing picture quality.

Furthermore, because LED displays can quickly switch the color of each pixel, they display dynamic images more clearly. LED displays also have higher brightness and can display clearly in sunlight, making them suitable for outdoor use, such as shop signs and billboards.

Character Encoding Standards

Text data is converted into binary encoding that computers can understand and process through character encoding. These encoding standards ensure consistent representation of different languages, scripts, and symbols in computer systems.

Some common character encoding standards include:

• ASCII (American Standard Code for Information Interchange): The earliest character encoding standard, using 7-bit binary encoding, covering basic English letters, numbers, and symbols.
• Unicode: A universal character encoding standard designed to unify almost all character sets and symbols in the world. It assigns a unique code point to each character and supports multiple encoding methods.
• UTF-8, UTF-16, etc.: Unicode encoding schemes used to map Unicode code points to storable and transmittable byte sequences.
• ISO-8859 Series: Encoding standards covering various European language character sets.
• GBK, GB2312, etc.: Chinese character set encoding standards used to represent Chinese characters and symbols.

Character encoding standards play a crucial role in text processing, web display, software development, and internationalization. Understanding different character encoding standards can help ensure correct transmission and display of text data across different systems and platforms.

1. ASCII (American Standard Code for Information Interchange)

ASCII code is a character encoding standard widely used in early computer systems. It was primarily designed for English text, so characters or special symbols from other languages were not included in the original ASCII character set.

ASCII code uses 7-bit binary representation, meaning it can represent up to 128 different characters (2^7). The most significant bit (8th bit) was unused in ASCII and typically used for parity checking in early communication systems.

Although ASCII was an important milestone in character encoding, its limitation to 128 characters prevented it from representing characters from various languages and scripts. As computers became more international, the demand for more comprehensive character encoding standards led to the development of Unicode, which can represent characters from almost all languages and scripts worldwide.

2. Unicode

Unicode's philosophy is to assign a "unique code point" to each character and symbol, giving each character a distinct position.

By design, the first 256 encodings are exactly the same as ISO-8859-1, to facilitate easy conversion of existing Western text. In the code charts on this page, you can see the Unicode code point (U+xxxx, where "xxxx" is a hexadecimal number) for each character.

Unicode space is divided into blocks, with each block's code corresponding to different languages. Unicode characters also include punctuation marks, mathematical and musical symbols, emojis, and more.

3. UTF-8 Encoding

UTF-8 is one of Unicode's encoding schemes. It has a good feature: for ordinary ASCII characters (0x00 to 0x7F), its encoding is exactly the same as ASCII.

The first 128 code points (ASCII) require one byte. The next 1,920 code points require two bytes for encoding, covering almost all the rest of the Latin alphabets. The remaining 61,440 code points belong to the Basic Multilingual Plane (BMP) and require three bytes for encoding, including most Chinese, Japanese, and Korean characters. And the 1,048,576 code points in other Unicode planes require four bytes for encoding, including emojis (pictographic symbols), less used CJK characters, various historical scripts, and mathematical symbols.

A "character" might require more than 4 bytes because it consists of multiple code points. For example, a national flag character requires 8 bytes because it is composed of two Unicode scalar values from outside the BMP.

The following diagram shows an example of UTF-8 encoding. For example, U+0024 only needs to be prefixed with 0 to form one byte, and the value remains unchanged; while U+00A3 requires two bytes. First, mark the high 5 bits of the original code point as green, and the low 6 bits as red, then add prefixes 110 and 10 respectively to form two complete bytes. And so on:

Fonts

Fonts are also encoded in binary format so that computers can read and understand them. Font files typically use specific file formats, and each format has its own specifications and structure for storing character encoding mappings and graphic data.

Character encoding mapping refers to mapping character encodings or Unicode code points to the font's character graphic data. Character graphic data contains information such as appearance, size, and position. This data exists in the form of vector graphics, describing the appearance of characters. After reading these glyph data, computers can render them, forming specific font styles.

Experiment

Principles