这是一篇 2017–2018 年的嵌入式学习笔记，保留当时的工具、代码和实验过程。 查看系列目录。

原图（暂不可用）

蜂鸣器

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
#include <reg51.h>

#define uint unsigned int
#define uchar unsigned char

sbit led = P0^0;
sbit sound = P2^0;
sbit key1 = P3^0;
sbit key2 = P3^2;
sbit key3 = P3^4;

void delay(uint timer)
{       
    uchar j = 124;
    while(timer--)
    {
        while(j--);
    }
}

void speak(uchar timer)
{
        uint i =0 ;
        uchar j = 0;
        for (i=400;i>0;i--)
        {
            sound = ~ sound;
            led = ~ led;
            for(j=timer;j>0;j--);
        }   
        led=1;
        sound=0;
}

void keyscan()
{       uchar num=0;
    
        if(num != P3)
        {
            num=P3;
            delay(10);
            if(num==P3)
            {
                    if(key1==0)
                    {
                        speak(80);
                    }
                    if(key2==0)
                    {
                        speak(160);
                    }
                    if(key3==0)
                    {
                        speak(240);
                    }
            }
        }
}

void main()
{
        led=1;
        sound=0;
        while(1)
        {
            keyscan();
        }
}

version2

显示函数做了略微的修改

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
void keyscan()
{       uchar num=0;
    
        if(num != P3)
        {
            num=P3;
            delay(10);
            if(num==P3)
            {
                    if(key1==0)
                    {
                        speak(90);
                    }
                    if(key2==0)
                    {
                        speak(90);
                        delay(10);
                        speak(90);
                    }
                    if(key3==0)
                    {
                        speak(90);
                        speak(240);
                    }
            }
        }
}

定时器模拟门铃

原图（暂不可用）

定时器模拟门铃

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
#include <reg51.h>

#define uint unsigned int
#define uchar unsigned char

sbit led = P0^0;
sbit sound = P2^0;
sbit key1 = P3^0;
uint num;


void delay(uint timer)
{       
    uchar j = 124;
    while(timer--)
    {
        while(j--);
    }
}

void timer1() interrupt 3
{
        sound = ~ sound;
        led = ~ led;
        num++;
        if(num<400)
        {
                TH1=(8192-700)/32;
                TL1=(8192-700)%32;
        } else if(num<800)
        {   
                TH1=(8192-1000)/32;
                TL1=(8192-1000)%32;
        } else
        {
                TR1=0;
                num=0;
        }
            
            
}

void timer1_init()
{
        TMOD=0x00;
        TH1=(8192-700)/32;
        TL1=(8192-700)%32;
        ET1=1;
        EA=1;
}

void keyscan()
{       uchar key_num=0;
        led=1;
        if(key_num != P3)
        {
            key_num=P3;
            delay(10);
            if(key_num==P3)
            {
                    if(key1==0)
                    {
                        TR1=1;
                    }
            }
        }
}

void main()
{       
        num=0;
        led=1;
        sound=0;
        timer1_init();
        while(1)
        {
            keyscan();
        }
}