学习单片机之---i2c总线程序 [复制链接]

i2c总线程序

  本程序是i2c总线读写一个字节的程序。在写过程序中，不一定非要检测i2c的应答位，可以直接延时过去就行，但是在读过程中必须给应答信号，读完发停止位，一定确认所发的信号都发上了。否则在连续地址读的过程中可能不会出错，但是在随机度过程中就会出错，我的程序就是在给停止信号时没有给上，24cxx一直在输出数据，结果读出错。找着问题后我的程序只加入了一条命令便完全正常。顺便提醒大家在调试24cxx时最好不要读些连续的地址，这样容易造成巧合因素导致疏忽，我这次犯的就是这个错误，程序一调试就通了，结果不再管它，到后来标定程序后算不出结果才有回头调试，折腾我两周。唉！郁闷呀！

/* *********************** EEPROM 24C256******************************* */
// 调试环境：时钟为DCO的时钟;频率4.00MHz
// 串行接口：P5.6 ------>SDA
// P5.7 ------>SCL
// 测试器件：MICROCHIP 24LC256
// 测试时间：2004-10-15
// 编写人员：石建华
/* *********************************************************************** */
#include <msp430x14x.h>
#define SDA_IN P5DIR &=~BIT6 // P5.6 IN
#define SDA_OUT P5DIR |=BIT6 // P5.6 OUT

#define SDA_LOW P5OUT &=~BIT6 // sda=0
#define SDA_HIGH P5OUT |=BIT6 // sda=1

#define SCL_IN P5DIR &=~BIT7 // P5.7 IN
#define SCL_OUT P5DIR |=BIT7 // P5.7 OUT

#define SCL_LOW P5OUT &=~BIT7
#define SCL_HIGH P5OUT |=BIT7

void delay (unsigned int TT)
{
for (;TT!=0;TT--);
}
unsigned char DATAR01,DATAR11,DATAR21,DATAR31,DATAR41;
void IIC_START (void)
{ SDA_OUT;
SDA_HIGH;
SCL_HIGH;
delay (50);
SDA_LOW;
delay (50);
SCL_LOW;
delay (50);
}
void IIC_STOP (void)
{ SDA_OUT;
SDA_LOW;
delay (50);
SCL_HIGH;
delay (50);
SDA_HIGH;
delay (50);
}
void IIC_ACK (void)
{ SDA_OUT;
SDA_LOW;
delay (50);
SCL_HIGH;
delay (50);
SCL_LOW;
delay (50);
}
void IIC_TX_DATA (unsigned char DATA)
{unsigned char Rn=8,RR=0x80;
SDA_OUT;
delay (50);
for (;Rn!=0;Rn--)
{
if ((DATA&RR)!=0)
SDA_HIGH;
else
SDA_LOW;
delay (50);
SCL_HIGH;
delay (50);
SCL_LOW;
delay (50);
RR>>=1;
}
SDA_HIGH;
delay (50);
SCL_HIGH;
delay (50);
SCL_LOW;
delay (50);
}

unsigned char IIC_RX_DATA (void)
{unsigned int Rn=8,DATA=0,RR=0x80;
SDA_IN; // 端口为输入
delay (50);
for (;Rn!=0;Rn--)
{
SCL_HIGH;
delay (50);

if ((P5IN&BIT6)!=0)
DATA|=RR;
else
DATA&=~RR;
RR>>=1;
SCL_LOW;
delay (50);
}

return DATA;
}
unsigned char READ_BYTE (unsigned int ADDR)
{ unsigned char DATA_R,ADDR_L,ADDR_H;
ADDR_L=ADDR%256;
ADDR_H=ADDR/256;
IIC_START ();
IIC_TX_DATA (0xA0);
delay(50);
IIC_TX_DATA (ADDR_H);
delay(50);
IIC_TX_DATA (ADDR_L);
delay(50);
IIC_START ();
IIC_TX_DATA (0xA1);
delay(50);
DATA_R=IIC_RX_DATA();
IIC_STOP ();
return DATA_R;
}

void WRITE_BYTE (unsigned int ADDR,unsigned char DATA_W)
{ unsigned char ADDR_H,ADDR_L;
ADDR_L=ADDR%256;
ADDR_H=ADDR/256;

SDA_OUT;
IIC_START ();
IIC_TX_DATA (0xA0); // E2PROM 片选

IIC_TX_DATA (ADDR_H); // 大于256BIT的EEPROM需加地址高位
IIC_TX_DATA (ADDR_L);
IIC_TX_DATA (DATA_W);
IIC_STOP ();
delay (0x3FFF); // 等待写时序
}

main()
{ unsigned int ADDRESS;
unsigned char DATAR0,DATAR1,DATAR2,DATAR3,DATAR4,DATAW;

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
DCOCTL = 0X73;
BCSCTL1= 0X87; // 设置时钟频率4.00MHz
P5DIR |=0XC0;
P5OUT |=0XC0;
DATAR01=0;
DATAR11=0;
DATAR21=0;
DATAR31=0;
DATAR41=0;
/* **********WRITE********** */
ADDRESS=0X0000;
DATAW=0X10;
WRITE_BYTE(ADDRESS,DATAW);
_NOP();
ADDRESS=0X0001;
DATAW=0X11;
WRITE_BYTE(ADDRESS,DATAW);
_NOP();
ADDRESS=0X0002;
DATAW=0X12;
WRITE_BYTE(ADDRESS,DATAW);
_NOP();
ADDRESS=0X0003;
DATAW=0X13;
WRITE_BYTE(ADDRESS,DATAW);
_NOP();
ADDRESS=0X0004;
DATAW=0X14;
WRITE_BYTE(ADDRESS,DATAW);
_NOP();
/* ***********READ************** */
ADDRESS=0X0005;
DATAR0=READ_BYTE(ADDRESS);
DATAR01 = DATAR0;
_NOP();
ADDRESS=0X0001;
DATAR1=READ_BYTE(ADDRESS);
DATAR11 = DATAR1;
_NOP();

ADDRESS=0X0002;
DATAR2=READ_BYTE(ADDRESS);
DATAR21 = DATAR2;
_NOP();

ADDRESS=0X0004;
DATAR3=READ_BYTE(ADDRESS);
DATAR31 = DATAR3;
_NOP();
ADDRESS=0X0000;
DATAR4=READ_BYTE(ADDRESS);
DATAR41 = DATAR4;
_NOP();
_NOP();
}