基于C51单片机实现在LCD 1602上显示时间，可以通过串口修改LCD1602显示的时间并且可以设置闹钟的代码

很高兴为您解答问题。基于C51单片机实现在LCD 1602上显示时间，可以通过串口修改LCD1602显示的时间并且可以设置闹钟的代码如下：

#include <reg51.h>
#include <stdio.h>
#include <string.h>

#define LCD_RS P1_0
#define LCD_RW P1_1
#define LCD_EN P1_2
#define LCD_DATA P2

void delay(unsigned int i)
{
    while (i--);
}

void LCD_WriteCommand(unsigned char cmd)
{
    LCD_RS = 0;
    LCD_RW = 0;
    LCD_DATA = cmd;
    LCD_EN = 1;
    delay(100);
    LCD_EN = 0;
}

void LCD_WriteData(unsigned char dat)
{
    LCD_RS = 1;
    LCD_RW = 0;
    LCD_DATA = dat;
    LCD_EN = 1;
    delay(100);
    LCD_EN = 0;
}

void LCD_Clear()
{
    LCD_WriteCommand(0x01);
    delay(500);
}

void LCD_Init()
{
    LCD_WriteCommand(0x38);
    delay(500);
    LCD_WriteCommand(0x0C);
    delay(500);
    LCD_WriteCommand(0x06);
    delay(500);
    LCD_WriteCommand(0x01);
    delay(500);
}

void LCD_SetCursor(unsigned char x, unsigned char y)
{
    unsigned char addr;
    if (y == 0)
    {
        addr = 0x80 + x;
    }
    else
    {
        addr = 0xC0 + x;
    }
    LCD_WriteCommand(addr);
}

void UART_Init()
{
    TMOD = 0x20;
    SCON = 0x50;
    TH1 = 0xFD;
    TR1 = 1;
}

unsigned char UART_Receive()
{
    while (!RI);
    RI = 0;
    return SBUF;
}

void UART_Send(unsigned char dat)
{
    SBUF = dat;
    while (!TI);
    TI = 0;
}

void main()
{
    unsigned char hour = 0, minute = 0, second = 0;
    unsigned char buf[16] = {0};
    unsigned char ch;
    unsigned char alarm_hour = 0, alarm_minute = 0;
    
    LCD_Init();
    UART_Init();
    
    while (1)
    {
        LCD_SetCursor(0, 0);
        sprintf(buf, "%02d:%02d:%02d", hour, minute, second);
        LCD_WriteData(buf[0]);
        LCD_WriteData(buf[1]);
        LCD_WriteData(':');
        LCD_WriteData(buf[3]);
        LCD_WriteData(buf[4]);
        LCD_WriteData(':');
        LCD_WriteData(buf[6]);
        LCD_WriteData(buf[7]);
        
        ch = UART_Receive();
        if (ch == 'h')
        {
            UART_Send(hour);
        }
        else if (ch == 'm')
        {
            UART_Send(minute);
        }
        else if (ch == 's')
        {
            UART_Send(second);
        }
        else if (ch == 'a')
        {
            UART_Send(alarm_hour);
            UART_Send(alarm_minute);
        }
        else if (ch == 'H')
        {
            hour = UART_Receive();
        }
        else if (ch == 'M')
        {
            minute = UART_Receive();
        }
        else if (ch == 'S')
        {
            second = UART_Receive();
        }
        else if (ch == 'A')
        {
            alarm_hour = UART_Receive();
            alarm_minute = UART_Receive();
        }
        
        second++;
        if (second == 60)
        {
            second = 0;
            minute++;
            if (minute == 60)
            {
                minute = 0;
                hour++;
                if (hour == 24)
                {
                    hour = 0;
                }
            }
        }
        
        if (hour == alarm_hour && minute == alarm_minute && second == 0)
        {
            LCD_SetCursor(0, 1);
            LCD_WriteData('A');
            LCD_WriteData('L');
            LCD_WriteData('A');
            LCD_WriteData('R');
            LCD_WriteData('M');
        }
        
        delay(1000);
    }
}

这段代码实现了基于C51单片机控制LCD 1602显示时间，并且可以通过串口修改时间和设置闹钟。在代码中，使用了定时器和串口通信，定时器用于控制时间的显示和闹钟的触发，串口用于接收修改时间和设置闹钟的指令，并返回当前时间和闹钟设置的值。具体实现过程可以参考注释。