In-depth analysis of the core technology and application cases of the RS-232/SPI/I ² C protocol analysis tool

RS-232, SPI and I ² C are three common serial communication protocols, which are widely used in various electronic devices and systems.

Understanding the working principles, technical characteristics and practical applications of these protocols is essential for developing efficient and reliable communication systems.

This article will deeply analyze the core technologies and application cases of these three protocol analysis tools, and comprehensively explore their technical details and application methods from principle to practice.

I. RS-232 protocol analysis tool.

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1. How it works.

RS-232 is a voltage-based asynchronous serial communication standard widely used for data transmission between computers and peripherals.

It performs full-duplex communication through two lines (the sender line and the receiver line), and the transmission rate is usually between 300 bps and 115.2 kbps.

RS-232 uses negative logic, that is, the logic "1" means -5V to -15V, and the logic "0" means + 5V to + 15V.

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2. Technical features.

- # Easy to use #: Due to the high degree of standardization of the RS-232 interface, the hardware implementation is relatively simple.

- # Long Distance Transmission #: suitable for point-to-point communication over short distances (usually no more than 15 meters).

- # Wide Application #: Commonly used for connecting computers with modems, printers and other devices.

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3. Application case.

Suppose we have an embedded system that needs to communicate with the PC, we can use the RS-232 interface to achieve this function.

The following is a simple code example showing how to configure and use the RS-232 interface for data sending and receiving in an embedded system.

#include 
#include 
#include 
#include 

int main() {
    int serial_port = open("/dev/ttyS0", O_RDWR); // 打开串口设备文件
    if (serial_port < 0) {
        perror("Failed to open the serial port");
        return 1;
    }

    struct termios tty;
    if (tcgetattr(serial_port, &tty) != 0) {
        perror("Failed to get attributes of the serial port");
        close(serial_port);
        return 1;
    }

    cfsetospeed(&tty, B9600); // 设置波特率为9600
    cfsetispeed(&tty, B9600);

    tty.c_cflag &= ~PARENB; // 无奇偶校验位
    tty.c_cflag &= ~CSTOPB; // 1个停止位
    tty.c_cflag &= ~CSIZE;
    tty.c_cflag |= CS8;     // 8个数据位

    tty.c_cflag &= ~CRTSCTS; // 禁用硬件流控制
    tty.c_cc[VMIN] = 1;      // 读取至少1个字符
    tty.c_cc[VTIME] = 5;     // 等待最多0.5秒

    if (tcsetattr(serial_port, TCSANOW, &tty) != 0) {
        perror("Failed to set attributes of the serial port");
        close(serial_port);
        return 1;
    }

    char msg[] = "Hello, RS-232!";
    write(serial_port, msg, sizeof(msg)); // 发送数据

    char read_buf[256];
    int num_bytes = read(serial_port, &read_buf, sizeof(read_buf)); // 接收数据
    if (num_bytes > 0) {
        printf("Received: %s\n", read_buf);
    } else {
        perror("Failed to read from the serial port");
    }

    close(serial_port); // 关闭串口设备文件
    return 0;
}

II. SPI protocol analysis tool.

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1. How it works.

SPI (Serial Peripheral Interface) is a synchronous serial communication protocol that allows the master device to communicate with one or more slave devices in full duplex.

SPI uses four lines: main output slave input (MOSI), main input slave output (MISO), clock (SCK) and chip selection (SS).

Data is transmitted synchronously on the rising or falling edge of the clock signal.

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2. Technical features.

- # High Speed Transfer #: SPI supports high data transfer rates, usually up to a few Mbps.

- # Multi-slave device support #: A master device can communicate with multiple slave devices at the same time, and different slave devices can be distinguished by chip selection signals.

- # Simple Protocol #: The SPI protocol is relatively simple and easy to implement.

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3. Application case.

Assuming we have a microcontroller that needs to communicate with multiple sensors, we can use the SPI interface to achieve this.

The following is a simple code example showing how to configure and use the SPI interface in a microcontroller to exchange data with the sensor.

#include 

const int chipSelectPin = 10; // 定义片选引脚

void setup() {
    Serial.begin(9600); // 初始化串口通信
    SPI.begin(); // 初始化SPI接口
    pinMode(chipSelectPin, OUTPUT); // 设置片选引脚为输出模式
    digitalWrite(chipSelectPin, HIGH); // 确保片选引脚初始状态为高电平
}

void loop() {
    digitalWrite(chipSelectPin, LOW); // 选择从设备
    byte data = SPI.transfer(0x00); // 发送数据并接收响应
    digitalWrite(chipSelectPin, HIGH); // 取消选择从设备
    Serial.println(data, HEX); // 打印接收到的数据
    delay(1000); // 延时1秒
}

III. I ² C protocol analysis tool.

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1. How it works.

I ² C (Inter-Integrated Circuit) is a synchronous serial communication protocol, mainly used for short-distance, low-speed inter-chip communication.

I ² C uses two lines: the data line (SDA) and the clock line (SCL).

All devices connected to the bus share these two lines, and each device has a unique address.

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2. Technical features.

- # Multi-master multi-slave #: The I ² C bus supports a multi-master multi-slave architecture, allowing multiple master devices and multiple slave devices to coexist.

- # Automatic Arbitration #: When multiple master devices try to access the bus at the same time, the I ² C protocol automatically arbitrates to ensure that the communication does not conflict.

- # Low Power #: The I ² C bus is designed in low power mode for battery-powered devices.

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3. Application case.

Suppose we have an embedded system that needs to communicate with multiple sensors and actuators, we can use the I ² C interface to achieve this function.

The following is a simple code example showing how to configure and use the I ² C interface in a microcontroller to exchange data with the sensor.

#include 

void setup() {
    Wire.begin(); // 初始化I²C接口
    Serial.begin(9600); // 初始化串口通信
}

void loop() {
    Wire.beginTransmission(0x50); // 开始与地址为0x50的从设备通信
    Wire.write(0x00); // 发送寄存器地址
    Wire.endTransmission(); // 结束传输
    Wire.requestFrom(0x50, 1); // 请求1字节数据
    while (Wire.available()) { // 如果数据可用
        byte data = Wire.read(); // 读取数据
        Serial.println(data, HEX); // 打印接收到的数据
    }
    delay(1000); // 延时1秒
}

IV. Summary and Outlook.

RS-232, SPI and I ² C are three important serial communication protocols, each with unique advantages and application scenarios.

With an in-depth understanding of the working principles, technical features, and practical application cases of these protocols, developers can better utilize these tools to optimize their projects.

In the future, with the continuous development of IoT and embedded systems, these protocols will continue to play an important role in driving the continuous innovation and development of communication technology.