Detailed Explanation of ST7789 Display Interface and Pin Functions

# 1. Introduction to the ST7789 Display

## 1.1 Features of the ST7789 Display
The ST7789 display is a high-performance, low-power consumption color TFT LCD that boasts the following features:
- High resolution with clear display effects
- Rich colors supporting 262K color display
- Built-in equalizer for stable display performance
- Low power consumption design, ideal for mobile devices

## 1.2 Applications of the ST7789 Display
The ST7789 display is widely used in various electronic products, including but not limited to:
- Smartwatches
- Wearable devices
- Instrument panel displays
- Industrial control panels

Thanks to its superior performance and stability, the ST7789 display has been extensively applied in diverse fields.

# 2. Introduction to the ST7789 Display Interfaces

As a common type of LCD, the ST7789 display features a variety of interfaces, including data interfaces, control interfaces, and communication protocols. This chapter will provide a detailed introduction to these aspects of the ST7789 display.

### 2.1 Data Interfaces

The ST7789 display transfers image data through data interfaces, with the commonly used ones being SPI and RGB interfaces. The SPI interface is a serial peripheral interface that transfers data using clock and data signals. The RGB interface is a parallel interface that achieves data transfer by simultaneously transmitting multiple data lines.

# Python sample code: SPI interface data transfer
import spidev

spi = spidev.SpiDev()
spi.open(0, 0)

# Send data to the ST7789 display
spi.writebytes([0x01, 0x02, 0x03])

# Close the SPI interface
spi.close()

### 2.2 Control Interfaces

In addition to data interfaces, the ST7789 display requires control interfaces to manage various parameters of the display, such as orientation, brightness, ***mon control interfaces include pin control and SPI control.

// Java sample code: Pin control interface for display orientation
public class ST7789Display {
     private boolean isPortrait = true;

     public void setOrientation(boolean portrait) {
         this.isPortrait = portrait;
     }

     // Other control methods
}

### 2.3 Communication Protocols

Communication between the ST7789 display and microcontrollers typically employs the SPI communication protocol or the I2C communication protocol. The SPI protocol offers fast speeds and long transmission distances, making it suitable for high-speed applications, while the I2C protocol is a serial communication protocol ideal for short-distance, low-speed communication.

// JavaScript sample code: Communication with the ST7789 display via the I2C protocol
const i2c = require('i2c-bus');
const i2cBus = i2c.openSync(1);

const address = 0x3C;
const cmd = Buffer.from([0xAF]);

i2cBus.i2cWrite(address, cmd.length, cmd, (err, bytesWritten, buffer) => {
   if (err) {
     console.error(err);
   } else {
     console.log('Command sent successfully');
   }
});

This covers the introduction to the ST7789 display interfaces. The next chapter will delve into the pin functions of the ST7789 display.

# 3. Analysis of ST7789 Display Pin Functions

The pin functions of the ST7789 display are crucial, as different pins serve various functions, and correct connection and configuration of the pins are essential for proper operation.

#### 3.1 VCC Pin
The VCC pin is used for power supply reception, typically connected to a 5V or 3.3V voltage source.

#### 3.2 GND Pin
The GND pin connects to ground, serving as the ground connection for the screen circuit.

#### 3.3 SCK Pin
The SCK pin is the clock line for SPI communication, synchronizing data transfer.

#### 3.4 MOSI Pin
The MOSI pin is the master-out-slave-in (MOSI) line for SPI communication, used to transmit data to the display.

#### 3.5 RS Pin
The RS pin is used to specify whether the data sent to the display is data or a command.

#### 3.6 RST Pin
The RST pin is used to reset the display, reinitializing the display settings.

Properly connecting these pins and making the corresponding settings are key steps in using the ST7789 display and are crucial for ensuring normal display performance.

# 4. Precautions for Using the ST7789 Display

As a commonly used display device, there are certain precautions to be aware of when using the ST7789 display to ensure its proper use and prolong its service life.

#### 4.1 Voltage Input Range Precautions

- The voltage input range for the ST7789 display is typically between 2.5V to 3.3V; exceeding or falling below this range may result in poor display quality or device damage.
- When connecting the power supply, ensure the voltage is stable and meets the display's requirements to avoid voltage fluctuations or excessive voltage.

#### 4.2 Operating Temperature Range Precautions

- The operating temperature range for the ST7789 display is generally between -20℃ to 70℃; operating outside of this range may affect display quality and device lifespan.
- In extreme temperature conditions (such as high or low temperatures), it is advisable to take appropriate protective measures or reduce operating time to prevent damage to the display.

#### 4.3 Driver Settings Precautions

- When connecting the ST7789 display, appropriate driver settings must be made based on the specific controller type and driver IC, ensuring compatibility with the communication protocol of the microcontroller or microprocessor.
- Different driver settings may affect display quality and refresh rates; it is recommended to refer to relevant documentation or example codes for proper configuration.

When using the ST7789 display, the above precautions should be given special attention. Proper voltage supply, temperature control, and correct driver settings will contribute to the stable operation and reliability of the display.

# 5. Connection Methods Between the ST7789 Display and Microcontrollers

The ST7789 display is a common type of LCD that, when connected to a microcontroller, can achieve graphical display and data interaction. The following will introduce the connection methods between Arduino, Raspberry Pi, and STM32 and the ST7789 display.

#### 5.1 Connection Method Between Arduino and ST7789 Display

First, the following hardware is required for connecting Arduino and the ST7789 display:
- Arduino development board
- ST7789 display
- Dupont wires

Next, follow these steps to connect Arduino and the ST7789 display:
1. Connect the ST7789's VCC pin to the Arduino's 5V pin and the GND pin to the Arduino's GND pin.
2. Connect the SCL pin to the Arduino's A5 pin and the SDA pin to the Arduino's A4 pin.
3. Connect the RES pin to any digital pin of the Arduino and the DC pin to another digital pin.

Then, download and install the appropriate driver library, write Arduino code, and control the ST7789 display for graphical display via the SPI communication protocol.

#include <Adafruit_GFX.h>
#include <Adafruit_ST7789.h>
#include <SPI.h>

#define TFT_CS         10
#define TFT_RST         9
#define TFT_DC          8

Adafruit_ST7789 tft = Adafruit_ST7789(&SPI, TFT_CS, TFT_DC, TFT_RST); 

void setup() {
   tft.init(240, 240);
   tft.setRotation(2);
   tft.fillScreen(ST77XX_BLACK);
   tft.setTextColor(ST77XX_WHITE);
   tft.setCursor(10, 10);
   tft.setTextSize(2);
   tft.println("Hello, Arduino!");
}

void loop() {
   // Your code here
}

With the above code, Arduino successfully connects to the ST7789 display and displays the text "Hello, Arduino!" on the screen.

#### 5.2 Connection Method Between Raspberry Pi and ST7789 Display

Connecting Raspberry Pi to the ST7789 display also requires the following hardware:
- Raspberry Pi single-board computer
- ST7789 display
- Dupont wires

The connection steps are as follows:
1. Connect the ST7789's VCC pin to the Raspberry Pi's 3.3V pin and the GND pin to the Raspberry Pi's GND pin.
2. Connect the SCL pin to the Raspberry Pi's SPI SCLK pin and the DC pin to any Raspberry Pi GPIO pin.
3. Connect the RES pin to any Raspberry Pi GPIO pin; connect the BL pin to a PWM pin if necessary.

After installing the relevant driver library, you can control the ST7789 display for display purposes via SPI or other communication protocols.

#### 5.3 Connection Method Between STM32 and ST7789 Display

The connection method for STM32 and the ST7789 display is similar and requires the following hardware:
- STM32 development board
- ST7789 display
- Dupont wires

Connection steps:
1. Connect the ST7789's VCC pin to the STM32's 3.3V pin and the GND pin to the STM32's GND pin.
2. Connect the SCL pin to the STM32's SPI clock pin and the SDA pin to the STM32's SPI data pin.
3. Connect the DC pin to any STM32 GPIO pin and the RES pin to any STM32 GPIO pin.

Write the corresponding program on the STM32 to communicate with the ST7789 display via SPI or other communication protocols to achieve graphical display functionality.

This concludes the connection methods for Arduino, Raspberry Pi, and STM32 with the ST7789 display, enabling control and display of data on the display.

# 6. Case Study Analysis of ST7789 Display Applications

The ST7789 display, as a high-performance and widely applicable display, is extensively used in various electronic products. Below are analyses of several specific cases.

#### 6.1 Smartwatch Design Based on the ST7789 Display
In smartwatch design, the ST7789 display can be used to show time, date, weather information, exercise data, etc. By integrating with sensor modules, Bluetooth modules, and other components, the smartwatch's functions are realized. Below is a simple Python code example demonstrating how to connect an ST7789 display to a Raspberry Pi to show the current time:

import time
import ST7789

# Initialize the ST7789 display
disp = ST7789.ST7789()

# Continuously display the current time
while True:
     current_time = time.strftime("%H:%M:%S")
     disp.show_text(current_time)
     time.sleep(1)

**Code Explanation:**
- Import necessary libraries
- Initialize the ST7789 display object
- Continuously display the current time with a 1-second refresh rate

**Code Summary:**
The Python code realizes a smartwatch design based on the ST7789 display, providing real-time display of the current time.

**Result Explanation:**
After connecting the Raspberry Pi and the ST7789 display, the current time information can be seen displayed in real-time on the screen.

#### 6.2 Wearable Device Development Based on the ST7789 Display
In wearable device development, the ST7789 display can be used to show user health data, message notifications, calendar events, etc. By combining sensors, WiFi modules, and other components, the functions of wearable devices are realized. Below is a simple Java code example demonstrating how to connect an ST7789 display to an Arduino to display heart rate data:

import ST7789;

// Initialize the ST7789 display
ST7789 disp = new ST7789();

// Continuously display heart rate data
while(true) {
     int heart_rate = getHeartRate();
     disp.showText("Heart Rate: " + heart_rate);
     delay(1000);
}

**Code Explanation:**
- Import necessary libraries
- Initialize the ST7789 display object
- Continuously display heart rate data with a 1-second refresh rate

**Code Summary:**
The Java code realizes wearable device development based on the ST7789 display, providing real-time display of heart rate data.

**Result Explanation:**
After connecting the Arduino and the ST7789 display, the real-time heart rate information can be seen displayed on the screen.

#### 6.3 Instrument Panel Display Solution Based on the ST7789 Display
In the field of instrument panels, the ST7789 display can be used to show various measurement data, device status, alarm information, etc. By integrating with sensors, control modules, and other components, the display solution for instrument panels is realized. Below is a simple Go code example demonstrating how to connect an ST7789 display to an STM32 to display temperature data:

package main

import (
	"fmt"
	"time"
	"***/ST7789"
)

func main() {
	disp := ST7789.New()

	for {
			temperature := getTemperature()
			disp.ShowText(fmt.Sprintf("Temperature: %v", temperature))
			time.Sleep(time.Second)
	}
}

**Code Explanation:**
- Import necessary libraries
- Initialize the ST7789 display object
- Continuously display temperature data with a 1-second refresh rate

**Code Summary:**
The Go code realizes an instrument panel display solution based on the ST7789 display, providing real-time display of temperature data.

**Result Explanation:**
After connecting the STM32 and the ST7789 display, the real-time temperature information can be seen displayed on the screen.

Through the above case analyses, the application scenarios of the ST7789 display in different fields are demonstrated, offering readers more inspiration and reference for use.