使用单片机AT89C51进行温度报警器代码

以下是一个基于AT89C51单片机的温度报警器代码，当温度超过设定的阈值时，会触发报警器。

#include <reg51.h>

#define DATA_PORT P0
sbit SDA = P2^0;    // I2C数据线
sbit SCL = P2^1;    // I2C时钟线

void delay(int t)   // 延时函数
{
    int i, j;
    for (i = 0; i < t; i++) {
        for (j = 0; j < 100; j++);
    }
}

void i2c_start()    // I2C起始信号
{
    SDA = 1;
    SCL = 1;
    delay(1);
    SDA = 0;
    delay(1);
    SCL = 0;
}

void i2c_stop()     // I2C停止信号
{
    SDA = 0;
    delay(1);
    SCL = 1;
    delay(1);
    SDA = 1;
}

unsigned char i2c_write(unsigned char dat)  // I2C写数据
{
    unsigned char i, ack;
    for (i = 0; i < 8; i++) {
        if (dat & 0x80) {
            SDA = 1;
        } else {
            SDA = 0;
        }
        delay(1);
        SCL = 1;
        delay(1);
        SCL = 0;
        dat <<= 1;
    }
    SDA = 1;
    delay(1);
    SCL = 1;
    delay(1);
    ack = SDA;
    SCL = 0;
    return ack;
}

unsigned char i2c_read()    // I2C读数据
{
    unsigned char i, dat;
    for (i = 0; i < 8; i++) {
        SDA = 1;
        delay(1);
        SCL = 1;
        delay(1);
        dat <<= 1;
        if (SDA) {
            dat |= 0x01;
        }
        SCL = 0;
    }
    return dat;
}

unsigned char ds18b20_init()    // DS18B20初始化
{
    unsigned char i;
    DATA_PORT = 0xff;
    delay(100);
    DATA_PORT = 0x00;
    delay(500);
    DATA_PORT = 0xff;
    delay(100);
    i = DATA_PORT;
    delay(500);
    return i;
}

void ds18b20_write(unsigned char dat)   // DS18B20写数据
{
    unsigned char i;
    for (i = 0; i < 8; i++) {
        DATA_PORT = 0x00;
        delay(2);
        if (dat & 0x01) {
            DATA_PORT = 0xff;
        } else {
            DATA_PORT = 0x00;
        }
        delay(60);
        DATA_PORT = 0xff;
        dat >>= 1;
    }
}

unsigned char ds18b20_read()   // DS18B20读数据
{
    unsigned char i, dat;
    for (i = 0; i < 8; i++) {
        DATA_PORT = 0x00;
        delay(2);
        DATA_PORT = 0xff;
        delay(10);
        dat >>= 1;
        if (DATA_PORT) {
            dat |= 0x80;
        }
        delay(50);
    }
    return dat;
}

void ds18b20_convert()  // DS18B20温度转换
{
    ds18b20_init();
    ds18b20_write(0xcc);
    ds18b20_write(0x44);
}

unsigned int ds18b20_read_temperature()    // DS18B20读温度
{
    unsigned char temp1, temp2;
    unsigned int temp;
    ds18b20_init();
    ds18b20_write(0xcc);
    ds18b20_write(0xbe);
    temp1 = ds18b20_read();
    temp2 = ds18b20_read();
    temp = temp2;
    temp <<= 8;
    temp |= temp1;
    return temp;
}

void i2c_write_byte(unsigned char addr, unsigned char dat)   // I2C写一个字节
{
    i2c_start();
    i2c_write(0x90);
    i2c_write(addr);
    i2c_write(dat);
    i2c_stop();
}

unsigned char i2c_read_byte(unsigned char addr)  // I2C读一个字节
{
    unsigned char dat;
    i2c_start();
    i2c_write(0x90);
    i2c_write(addr);
    i2c_start();
    i2c_write(0x91);
    dat = i2c_read();
    i2c_stop();
    return dat;
}

void main()
{
    unsigned int temp;
    unsigned char temp1, temp2;
    unsigned char alarm = 0;
    i2c_start();
    i2c_write_byte(0x01, 0x00); // 温度阈值：25°C
    i2c_stop();
    while (1) {
        ds18b20_convert();
        delay(500);
        temp = ds18b20_read_temperature();
        temp1 = temp >> 8;
        temp2 = temp & 0xff;
        i2c_write_byte(0x00, temp1);    // 写入温度高位
        i2c_write_byte(0x01, temp2);    // 写入温度低位
        if (temp > 250) {   // 温度超过阈值
            if (!alarm) {   // 如果还没有报警
                P1 = 0x01;  // 报警器响
                alarm = 1;  // 标记已经报警
            }
        } else {
            P1 = 0x00;      // 关闭报警器
            alarm = 0;      // 标记没有报警
        }
        delay(500);
    }
}

在这个代码中，我们使用了DS18B20数字温度传感器来测量环境温度，并且使用了I2C总线来与EEPROM进行通信，将温度值和温度阈值写入EEPROM中，实现了温度报警功能。当温度超过设定的阈值时，会触发报警器。