I2C 总线 ——E2PROM
IIC总线工作原理
I2C总线进行数据传送时，时钟信号为高电平期间，数据线上的数据必须保持稳定，只有在时钟线上的信号为低电平期间，数据线上的高电平或低电平状态才允许变化。
起始和终止信号 ：SCL线为高电平期间，SDA线由高电平向低电平的变化表示起始信号；SCL线为高电平期间，SDA线由低电平向高电平的变化表示终止信号。
数据传送格式（1）字节传送与应答
每一个字节必须保证是8位长度。数据传送时，先传送最高位（MSB），每一个被传送的字节后面都必须跟随一位应答位（即一帧共有9位）。如果一段时间内没有收到从机的应答信号，则自动认为从机已正确接收到数据。
void respons() //回应信号
{
uchar i=0;SCL=1;delay();
while((SDA==1)&&(i<255))i++;
SCL=0;delay();
}
应答信号时序看了肾长时间，DATA IN 和DATA OUT 是一条总线，DATA IN 默认为高电平，while()循环不停循环等待DATA 的信号应答 ，如有应答此时的DATA 会被置为低电平
#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
sbit sda=P2^0;
sbit scl=P2^1;
void delay2(uchar x)
{
unsigned char i,j;
for(i=x;i>0;i--)
for(j=110;j>0;j--)
;
}
void delay()
{;;}
void start()
{
scl=1;
delay();
sda=1;
delay();
sda=0;
delay();
}
void stop()
{
scl=1;
delay();
sda=0;
delay();
sda=1;
delay();
}
void respons()
{
unsigned char i;
scl=0;
delay();
sda=1;
delay();
scl=1;
delay();
while((sda==1)&&(i<250))
i++;
scl=0;
delay();
}
void write_byte(uchar dat)
{
unsigned char temp,i;
temp=dat;
// sda=1;
// delay();
// scl=0;
//// delay();
for(i=0;i<8;i++)
{
temp=(temp<<1);
scl=0;
delay();
sda=CY;
delay();
scl=1;
delay();
//scl=0; 错误一: 写时序，先保持SCl为低电平，在写入数据保持稳定再置为高电平，
//读时序时，先SCL=1再保持数据总线的数据稳定，再SCl再置为低电平
// delay(10);
}
scl=0;
delay();
sda=1;
delay();
}
void init()
{
sda=1;
delay();
scl=1;
delay();
}
uchar read_byte()
{
unsigned char i,temp;
sda=1;
delay();
scl=0;
delay();
for(i=0;i<8;i++)
{
scl=1;
delay();
temp=(temp<<1)|sda;
delay();
/// scl=1;
// delay();
// temp=(temp<<1)|sda;
scl=0;
delay();
}
sda=1;
delay();
scl=1;
delay();
return temp;
}
void write_add(uchar address,uchar date)
{
start();
write_byte(0xa0);
respons();
write_byte(address);
respons();
write_byte(date);
respons();
stop();
}
uchar read_add(uchar address)
{
uchar date;
start();
write_byte(0xa0);
respons();
write_byte(address);
respons();
start();
write_byte(0xa1);
respons();
date=read_byte();
stop();
return date;
}
void main()
{
P1=0x00;
// while(1);
init();
write_add(14,0xaa);
delay2(100);
P1=read_add(14);
while(1);
}
注意只能是
delay()
{;;}
延迟太长无法存储
数码管记忆显示，EEPROM
#include<reg52.h>
#define uchar unsigned char
unsigned char code table[]={ 0xc0,0xf9,0xa4,0xb0, 0x99,0x92,0x82,0xf8, 0x80,0x90,0x88,0x83, 0xc6,0xa1,0x86,0x8e,0x7f};
//unsigned char code table[]={ 0xc0,0xf9,0xa4,0xb0, 0x99,0x92,0x82,0xf8, 0x80,0x90,0x88,0x83, 0xc6,0xa1,0x86,0x8e,0x7f};
sbit sda=P2^0;
sbit scl=P2^1;
uchar a;
bit flag;
void delay()
{ ;; }
void delay2(unsigned int x)
{
unsigned int i,j;
for(i=x;i>0;i--)
for(j=0;j<110;j++)
;
}
uchar time,count;
void start() //开始信号
{
sda=1;
delay();
scl=1;
delay();
sda=0;
delay();
}
void stop() //停止
{
sda=0;
delay();
scl=1;
delay();
sda=1;
delay();
}
void respons() //应答
{
uchar i;
scl=1;
delay();
while((sda==1)&&(i<250))i++;
scl=0;
delay();
}
void init()
{
sda=1;
delay();
scl=1;
delay();
TMOD=0x01;
EA=1;
ET0=1;
TR0=1;
TH0=(65536-50000)/256;
TL0=(65536-50000)%256;
}
void write_byte(uchar date)
{
uchar i,temp;
temp=date;
for(i=0;i<8;i++)
{
temp=temp<<1;
scl=0;
delay();
sda=CY;
delay();
scl=1;
delay();
}
scl=0;
delay();
sda=1;
delay();
}
uchar read_byte()
{
uchar i,k;
scl=0;
delay();
sda=1;
delay();
for(i=0;i<8;i++)
{
scl=1;
delay();
k=(k<<1)|sda;
scl=0;
delay();
}
return k;
}
void delay1(uchar x)
{
uchar a,b;
for(a=x;a>0;a--)
for(b=100;b>0;b--)
;
}
void write_add(uchar address,uchar date)
{
start();
write_byte(0xa0);
respons();
write_byte(address);
respons();
write_byte(date);
respons();
stop();
}
uchar read_add(uchar address)
{
uchar date;
start();
write_byte(0xa0);
respons();
write_byte(address);
respons();
start();
write_byte(0xa1);
respons();
date=read_byte();
stop();
return date;
}
void main()
{
init();
time=read_add(2);//记忆读取
if(time==15)
{
time=0;
}
while(1)
{
P1=table[time];
if(flag==1)
{
flag=0;
write_add(2,time); //每隔一秒写入一个数据
}
}
}
void time0() interrupt 1
{
TH0=(65536-50000)/256;
TL0=(65536-50000)%256;
count++;
if(count==20)
{
count=0;
time++;
flag=1;
if(time==15)
{
time=0;
}
}
}