//模擬I2C總線與sht15傳感器通信

//將測得數(shù)據(jù)通過串口輸出(成功)
//未加 CRC校驗

#include

#define SCL RG0//時鐘總線
#define DATA RG1//數(shù)據(jù)總線
#define SCL_DR TRISG0//時鐘方向
#define DATA_DR TRISG1//數(shù)據(jù)方向
#define out 0
#define in 1
#define MT 0x03//Measure Temperature
#define MH 0x05//Measure Humidity
#define RR 0x07//Read Status Register
#define WR 0x06//Write Status Register

/**********全局變量***************/
bit ack=0;
unsigned int measureresult=0; //存儲測量結(jié)果
float temperature=0; //溫度值
float humidity=0; //濕度值

/*********delay function**********/
void nops()
{
asm("nop");
asm("nop");
}
void nopss()
{
asm("nop");
asm("nop");
asm("nop");
asm("nop");
}

void i2c_wait()
{
unsigned char j;
for(j=0;j<10;j++)
asm("nop");
}

void delay(unsigned int n) //帶參數(shù)延時函數(shù)
{
unsigned int i,j;
for(j=0;jfor(i=0;i<100;i++);
}
/********************************/
void SHT15_start()
{
DATA_DR=out;
SCL_DR=out;

DATA=1;
SCL=1;
nopss();
DATA=0;
nopss();
SCL=0;
nopss();
SCL=1;
nopss();
DATA=1;
nopss();
SCL=0;
}
void SHT15_reset()
{unsigned char i;
DATA_DR=out;
SCL_DR=out;
DATA=1;SCL=0;///reset the sensor
for(i=0;i<9;i++)
{
SCL=1;
nops();
SCL=0;
}
SHT15_start();

}
char command(unsigned char temp)
{

ack=0;
unsigned char i;
unsigned int j;
for(i=0x80;i>0;i/=2)
{
if(temp&i) DATA=1;
else DATA=0;
SCL=1;
nops();
SCL=0;
}
DATA_DR=in;
SCL=1;
nops();
SCL=0;
ack=DATA;
//DATA=1;

while(DATA);
return ack;

}
unsigned int read_data()
{
unsigned char a,data1=0,data2=0,checksum=0;
unsigned int data=0;
for(a=0x80;a>0;a/=2) ////前八位
{SCL=1;
if(DATA) data1=data1|a;
SCL=0;
nops();
}
DATA_DR=0;
DATA=0; ////應答
SCL=1;
nopss();
SCL=0;
DATA_DR=1;

for(a=0x80;a>0;a/=2)//////后八位
{
SCL=1;
if(DATA) data2=data2|a;
SCL=0;
nops();
}
DATA_DR=0;
DATA=0; ////應答
SCL=1;
nopss();
SCL=0;
DATA_DR=1;
for(a=0x80;a>0;a/=2) /////校驗和
{
SCL=1;
if(DATA) checksum=checksum|a;
SCL=0;
}

DATA=1;////應答，傳輸結(jié)束。
SCL=1;
nopss();
SCL=0;

/////校驗

data=data1*256+data2;
return data;

}

float calculate(unsigned char temp,unsigned int data)
{
float result=0;
if(temp==MH)
{
result= -4 + 0.0405*data - 2.8*0.000001*data*data;
}
if(temp==MT)
{
result=-40 + 0.01 * data;
}
return result;
}

void USART_init()//帶形參的USART發(fā)送函數(shù)
{
//GIE=0;
//PEIE=0;
//TRISC7=1;
//TRISC6=0;
TXIE=0;//關閉中斷
TXSTA=0x06; //發(fā)送狀態(tài)寄存器設置
SPBRG=0x19; //波特率設為38400bps

}
void USART_tx(unsigned char byte)
{
SPEN=1;
while(!TRMT); //檢測TSR寄存器是否為空
TXREG=byte; //將待發(fā)數(shù)據(jù)給發(fā)送寄存器
TXEN=1; //啟動發(fā)送使能
while(!TRMT); //等待發(fā)關完一字節(jié)數(shù)據(jù)
TXEN=0; //關閉發(fā)送使能

}

/*主函數(shù)*/
void main()
{

//SHT15_start();

USART_init();
for(;;)
{
SHT15_reset();
command(MH);
measureresult=read_data();
humidity=calculate(MH,measureresult);
//USART_tx((unsigned char)humidity);
//delay(10);
//USART_tx('a');
delay(100);
}

}
/***************************************/
/*****Interrupt ServiceRoutine**********/
/***************************************/
void interrupt isr() //不能去掉，否則無法正常發(fā)送數(shù)據(jù)
{

}