Analysis of the Infrared Touchscreen Driver Principle for ST7789 Display Screen

# 1. Introduction to ST7789 Display

## 1.1 Features of ST7789 Display
The ST7789 display is a high-performance TFT-LCD screen driver chip with the following features:
- High resolution for clear and delicate display effects
- Fast refresh rate with excellent response speed
- Supports RGB interface, making it easy to integrate into various systems

## 1.2 Applicability of ST7789 Display
The ST7789 display is suitable for a wide range of embedded systems and consumer electronics, such as smartwatches and smart home control panels. Its outstanding performance and stability make it a preferred choice for extensive applications.

# 2. Overview of Infrared Touch Screen Technology

Infrared touch screen technology, as an advanced touch technology, boasts numerous unique advantages. Below, we delve into the principles and operations of infrared touch screens and compare them with traditional touch screens.

### 2.1 Principles and Operations of Infrared Touch Screens

Infrared touch screens work by installing a pair of infrared emitters and receivers on the edges or surface of the LCD screen. The emitters emit infrared light, and when an object touches the screen surface, the infrared light is blocked, causing the receiver to fail to detect the light. By detecting the interruption of infrared light, the touch position can be determined. This principle results in infrared touch screens being highly accurate and stable.

### 2.2 Comparison of Infrared Touch Screens with Traditional Touch Screens

Compared to traditional capacitive or resistive touch screens, infrared touch screens have the following advantages:

- **Unaffected by surface material**: Infrared touch screens can penetrate any material on the screen surface, such as gloves, glass, etc.
- **Strong resistance to pollution**: As the infrared beams are non-contact, infrared touch screens are less affected by dust and liquid contamination.
- **High precision and sensitivity**: Infrared touch screens can achieve high touch accuracy and sensitivity, suitable for scenarios requiring precise interaction.

Through these comparisons, infrared touch screens have clear advantages in specific scenarios, providing users with a more convenient and accurate touch experience.

# ***bining ST7789 Display with Infrared Touch Screens

This chapter explores the integration of ST7789 displays with infrared touch screens and their related advantages and应用场景.

#### 3.1 Integration Methods of ST7789 Display and Infrared Touch Screens
ST7789 displays and infrared touch screens can be integrated through serial communication, among other methods. By stacking the infrared touch screen on top of the ST7789 display, touch screen functionality can be achieved without affecting the display's normal operation. Infrared touch screens support multi-touch and gesture recognition, and when combined with ST7789 displays, they offer a richer user interaction experience.

#### 3.2 Analysis of Advantages and Application Scenarios
The advantages of combining ST7789 displays with infrared touch screens are mainly reflected in the following aspects:

- Provides a more intuitive and convenient method of operation, allowing users to interact with displayed content through touch screens.
- Achieves multi-touch and gesture recognition functions, enhancing the user experience.
- Realizes display and touch screen functions without taking up additional space, saving device volume.

应用场景 include but are not limited to smart home control panels, industrial control equipment, medical equipment, and other products that require display and touch interaction.

By combining ST7789 displays with infrared touch screens, products can be provided with more intelligent and user-friendly operating methods, enhancing the user experience and product competitiveness.

# 4. Driving Principle of ST7789 Display

ST7789 display is a common color TFT LCD with high definition, rich colors, and good display effects, widely used in various fields.

#### 4.1 Analysis of ST7789 Display Working Principle

The working principle of the ST7789 display mainly involves communication with the main control chip through the SPI interface. The main control chip sends instructions or data to the ST7789 display to control the displayed content. The entire display consists of multiple pixels, each containing the three primary colors—red, green, and blue. By controlling the color and brightness of each pixel, various images and text can be displayed. In addition, the display includes a display buffer for storing content to be displayed, achieving image display through a line-by-line refresh method.

#### 4.2 Key Points of Driver Design

When designing the ST7789 display driver program, the following points need attention:

1. **Initialization Settings**: Before using the display, it must be initialized, including settings for display mode, pixel format, orientation, and other parameters.

2. **Data Transmission**: When transmitting data through the SPI protocol with the main control chip, attention must be paid to timing, data format, etc., to ensure correct data transmission.

3. **Refresh Display**: By continuously updating the content in the display buffer and refreshing the display, a dynamic display effect can be achieved.

4. **Performance Optimization**: Performance can be optimized, and power consumption can be reduced by adjusting the update strategy of the display content and lowering the refresh rate.

In summary, understanding the working principle of the ST7789 display and designing a reasonable driver program based on its characteristics can better leverage its display effects and enhance the user experience.

# 5. Driving Principle of Infrared Touch Screens

Infrared touch screens, as a common touch screen technology, mainly rely on the collaborative work of infrared sensors and control circuits. Here is a detailed analysis of the driving principle of infrared touch screens:

#### 5.1 Infrared Touch Screen Driver Circuit Design

Infrared touch screens typically consist of emitters and receivers. The emitters emit infrared light onto the screen surface, while the receivers detect the infrared light blocked by fingers to determine the touch position. The driver circuit often includes modules such as AD converters, filters, and digital signal processors for processing infrared signals and converting them into touch coordinates.

# Example code for Infrared Touch Screen Driver Circuit Design

def detect_touch():
     infrared_light = read_infrared_sensor()
     if infrared_light < threshold:
         return "Touch Detected"
     else:
         return "No Touch Detected"

def read_infrared_sensor():
     # Read the value of the infrared sensor
     return sensor_value

# Main program
threshold = 100
touch_status = detect_touch()
print(touch_status)

**Code Summary:**
- Touch status can be detected by reading the value of the infrared sensor.
- Set a threshold to determine if a touch has occurred based on the sensor value.

#### 5.2 Key Points in Developing Infrared Touch Screen Driver Programs

When developing the infrared touch screen driver program, the following points need consideration:

1. Determine the sampling frequency and sensitivity of the infrared sensors to obtain accurate touch position information.
2. Filter and process the infrared signal to ensure the accuracy and stability of touch detection.
3. Optimize touch algorithms to improve touch response speed and accuracy, enhancing the user experience.

By focusing on these development points, the infrared touch screen driver program can be better designed and implemented, providing stable and reliable support for touch interaction.

In practical applications, infrared touch screens are widely used in intelligent devices and interactive displays. In the driver program development process, developers should flexibly apply these points based on specific needs to achieve better touch interaction effects.

# 6. Case Analysis

In this chapter, we will analyze the application scenarios and effect display of ST7789 displays and infrared touch screens through real-life cases.

#### 6.1 How to Use ST7789 Displays and Infrared Touch Screens in Real Products

To demonstrate how to use ST7789 displays and infrared touch screens in real products, we will use the Raspberry Pi as a demonstration platform to build a simple interactive interface. First, we need to connect the ST7789 display and infrared touch screen to the Raspberry Pi and then write the corresponding driver programs.

# Python sample code

import ST7789_display
import IR_touchscreen

# Initialize ST7789 display
display = ST7789_display.init()

# Initialize infrared touch screen
touchscreen = IR_touchscreen.init()

while True:
     # Get infrared touch screen coordinates
     x, y = touchscreen.get_touch_coordinates()

     # Display the touch point on the ST7789 display
     display.show_touch_point(x, y)

#### 6.2 Case Demonstration and Effect Display

In the above example, we implemented the combined application of ST7789 displays and infrared touch screens using the Raspberry Pi. When a user touches the infrared touch screen, the ST7789 display will immediately show the location of the touch point, achieving a simple interactive effect. This combined approach can be widely applied in smart homes, industrial control, medical equipment, and other fields, providing users with a more convenient and intuitive operating experience.

From the above case demonstration, we can see that the combination of ST7789 displays and infrared touch screens has high expandability and flexibility in practical applications, offering new possibilities for the interaction design of various products.