模拟I2C实现温湿度传感器SHT20的的no hold master的读取温度的程序

以下是模拟I2C实现SHT20温湿度传感器的no hold master的读取温度的程序示例：

#include <stdio.h>
#include <stdlib.h>
#include <wiringPi.h>

#define I2C_SDA_PIN 2
#define I2C_SCL_PIN 3
#define SHT20_I2C_ADDR 0x40

// 定义SHT20芯片命令
#define SHT20_MEASURE_TEMP_NO_HOLD 0xF3

// I2C总线初始化
void i2c_init() {
    wiringPiSetup();
    pinMode(I2C_SDA_PIN, OUTPUT);
    pinMode(I2C_SCL_PIN, OUTPUT);
}

// I2C总线开始信号
void i2c_start() {
    digitalWrite(I2C_SDA_PIN, HIGH);
    digitalWrite(I2C_SCL_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SDA_PIN, LOW);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
}

// I2C总线停止信号
void i2c_stop() {
    digitalWrite(I2C_SCL_PIN, LOW);
    digitalWrite(I2C_SDA_PIN, LOW);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SDA_PIN, HIGH);
    delayMicroseconds(5);
}

// I2C总线发送一个字节数据
void i2c_write_byte(unsigned char data) {
    int i;
    for (i = 0; i < 8; i++) {
        digitalWrite(I2C_SCL_PIN, LOW);
        delayMicroseconds(5);
        if (data & 0x80) {
            digitalWrite(I2C_SDA_PIN, HIGH);
        } else {
            digitalWrite(I2C_SDA_PIN, LOW);
        }
        delayMicroseconds(5);
        digitalWrite(I2C_SCL_PIN, HIGH);
        delayMicroseconds(5);
        data <<= 1;
    }
    digitalWrite(I2C_SCL_PIN, LOW);
    digitalWrite(I2C_SDA_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
}

// I2C总线读取一个字节数据
unsigned char i2c_read_byte() {
    unsigned char data = 0;
    int i;
    digitalWrite(I2C_SDA_PIN, HIGH);
    for (i = 0; i < 8; i++) {
        data <<= 1;
        digitalWrite(I2C_SCL_PIN, LOW);
        delayMicroseconds(5);
        digitalWrite(I2C_SCL_PIN, HIGH);
        delayMicroseconds(5);
        if (digitalRead(I2C_SDA_PIN)) {
            data |= 0x01;
        }
        delayMicroseconds(5);
    }
    digitalWrite(I2C_SCL_PIN, LOW);
    digitalWrite(I2C_SDA_PIN, HIGH);
    delayMicroseconds(5);
    return data;
}

// 从SHT20芯片读取温度
float sht20_read_temperature() {
    float temperature = 0;
    // 发送开始信号
    i2c_start();
    // 发送设备地址和写命令
    i2c_write_byte(SHT20_I2C_ADDR << 1);
    // 发送读取温度命令
    i2c_write_byte(SHT20_MEASURE_TEMP_NO_HOLD);
    // 等待转换完成
    delay(100);
    // 发送开始信号
    i2c_start();
    // 发送设备地址和读命令
    i2c_write_byte((SHT20_I2C_ADDR << 1) | 0x01);
    // 读取温度数据的高字节
    unsigned char temp_h = i2c_read_byte();
    // 发送ACK信号
    digitalWrite(I2C_SDA_PIN, LOW);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
    // 读取温度数据的低字节
    unsigned char temp_l = i2c_read_byte();
    // 发送NACK信号
    digitalWrite(I2C_SDA_PIN, HIGH);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, HIGH);
    delayMicroseconds(5);
    digitalWrite(I2C_SCL_PIN, LOW);
    delayMicroseconds(5);
    // 计算温度值
    int raw_temp = ((unsigned int)temp_h << 8) | temp_l;
    temperature = -46.85 + 175.72 * ((float)raw_temp / 65536.0);
    // 发送停止信号
    i2c_stop();
    return temperature;
}

int main() {
    // 初始化I2C总线
    i2c_init();
    // 读取温度并打印
    float temperature = sht20_read_temperature();
    printf("Temperature: %.2f\n", temperature);
    return 0;
}

这个程序使用了树莓派的wiringPi库来控制GPIO口模拟I2C总线，通过发送SHT20芯片的控制命令来读取温度数据。请根据具体硬件及引脚连接进行修改。