51单片机基于I2C总线的秒表模拟应用

  1 #include <reg51.h>
  2 typedef unsigned char uchar;
  3 typedef unsigned int uint;
  4 sbit scl = P3 ^ 0;
  5 sbit sda = P3 ^ 1;
  6 uchar second = 0;
  7 uchar count = 0;
  8 bit flag = 0;
  9 uchar code table[] =
 10 {
 11     0xFC, 0x60, 0xDA, 0xF2, 0x66, 0xB6, 0xBE, 0xE0, 0xFE, 0xF6, 0xEE, 0x3E, 0x9C, 0x7A, 0x9E, 0x8E
 12 };
 13 void Init(); //初始化总线
 14 void Start(); //开始
 15 void Stop(); //停止
 16 void Respons(); //响应位
 17 uchar ReadByte(); //读数据
 18 uchar ReadAddress(uchar address); //读地址
 19 void WriteByte(uchar dat); //写字节
 20 void WriteAddress(uchar address, uchar dat); //写地址
 21 void Display(); //显示数码管
 22 void Delay1ms(uchar m); //延时1ms
 23 void Delay(); //延时2个机器周期
 24 void main()
 25 {
 26     /* 初始化总线 */
 27     Init();
 28     /* 初始化LED */
 29     P1 = 0xff;
 30     /* 设置定时器 */
 31     TMOD = 0x01;
 32     TH0 = (65536 - 50000) / 256;
 33     TL0 = (65536 - 50000) % 256;
 34     /* 中断初始化 */
 35     EA = 1;
 36     ET0 = 1;
 37     /* 定时器开始 */
 38     TR0 = 1;
 39     /* 显示数码管并写入 */
 40     while(1)
 41     {
 42         if (flag == 1)
 43         {
 44             flag = 0;
 45             WriteAddress(2, second);
 46         }
 47         Display();
 48     }
 49 
 50 }
 51 void Init()
 52 {
 53     //空间状态时SCL与SDA均保持高电平
 54     sda = 1;
 55     Delay();
 56     scl = 1;
 57     Delay();
 58 }
 59 void Start()
 60 {
 61     //SCL高电平情况下,SDA下降沿启动
 62     sda = 1;
 63     Delay();
 64     scl = 1;
 65     Delay();
 66     sda = 0;
 67     Delay();
 68 }
 69 void Stop()
 70 {
 71     //SCL高电平情况下,SDA上升沿停止
 72     sda = 0;
 73     Delay();
 74     scl = 1;
 75     Delay();
 76     sda = 1;
 77     Delay();
 78 }
 79 void Respons()
 80 {
 81     //在SCL位为高电平时产生响应信号,数据传输正确时产生应答且SDA拉低
 82     uchar i;
 83     scl = 1; //此处scl拉高后在while循环中降低,参照时序图
 84     Delay();
 85     while ((sda == 1) && (i < 255))
 86     {
 87         //SDA拉低时跳出循环,表示数据传输正确,产生应答.如果在一段时间内未收到应答,则不再等待跳出循环
 88         i++;
 89         scl = 0;
 90         Delay();
 91     }
 92 }
 93 void WriteAddress(uchar address, uchar dat)
 94 {
 95     Start(); //开始
 96     WriteByte(0xA0); //写入 1010 0000 高4位为固定值,5-7位为A0 A1 A2,最低位0为写操作标识
 97     Respons();
 98     WriteByte(address); //写入 0000 0010
 99     Respons();
100     WriteByte(dat); //写入数据(秒数)
101     Respons();
102     Stop(); //停止
103 }
104 void WriteByte(uchar dat)
105 {
106     uchar i, temp;
107     temp = dat; //将dat读入temp
108     for (i = 0; i < 8; ++i)
109     {
110         temp = temp << 1; //temp左移,最高位移入CY
111         scl = 0; //SCL复位,等待最高位存入SDA后置位
112         Delay();
113         sda = CY; //CY在头文件中已规定,通过SDA发送bit
114         Delay();
115         scl = 1; //SCL置位,延迟2个机器周期后复位
116         Delay();
117     }
118     scl = 0; //为最后一个SCL高电平复位
119     Delay();
120     sda = 1; //一个字节数据发送完毕后置位准备响应
121     Delay();
122 }
123 uchar ReadAddress(uchar address)
124 {
125     uchar byte;
126     Start();
127     WriteByte(0xA0);
128     Respons();
129     WriteByte(address);
130     Respons();
131     Start();
132     WriteByte(0xA1); //写入地址 1010 0001,读写标志位1为读
133     Respons();
134     byte = ReadByte();
135     Stop();
136     return byte;
137 }
138 uchar ReadByte()
139 {
140     uchar i, k;
141     scl = 0;
142     Delay();
143     sda = 1;
144     Delay();
145     for (i = 0; i < 8; ++i)
146     {
147         scl = 1;
148         Delay();
149         k = (k << 1) | sda;
150         scl = 0;
151         Delay();
152     }
153     return k;
154 }
155 void Display()
156 {
157     P2 = 0xfe;
158     P1 = table[second % 10];
159     Delay1ms(1);
160     P2 = 0xfd;
161     // P1 = table[second / 10 %10];
162     P1 = table[second / 10];
163     Delay1ms(1);
164     // P2 = 0xfb;
165     // P1 = table[second / 100];
166     // Delay1ms(5);
167 }
168 void Delay()
169 {
170     ;;
171 }
172 void Delay1ms(uchar m) //使用1ms时二极管闪烁,此处将y=110改成y=50
173 {
174     uchar x, y;
175     for (x = m; x > 0; ++x)
176         for (y = 50; y > 0; --y)
177             ;
178 }
179 void time()interrupt 1
180 {
181     TH0 = (65536 - 50000) / 256;
182     TL0 = (65536 - 50000) % 256;
183     count++;
184     if (count == 20)
185     {
186         count = 0;
187         flag = 1;
188         second++;
189         if (second == 60)
190             second = 0;
191     }
192 }