sht7i.c

sht71瑞士公司生产的用来测量温湿度的芯片

//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
{ 
  unsigned char error=0;
  //s_transstart();                   //transmission start
   s_connectionreset();             //后加
  error+=s_write_byte(STATUS_REG_W);//send command to sensor
  error+=s_write_byte(*p_value);    //send value of status register
  return error;                     //error>=1 in case of no response form the sensor
}

//----------------------------------------------------------------------------------
char s_softreset(void)
//----------------------------------------------------------------------------------
// resets the sensor by a softreset 
{ 

  unsigned char error=0;  
  s_connectionreset();              //reset communication
  error+=s_write_byte(RESET);       //send RESET-command to sensor
  return error;                     //error=1 in case of no response form the sensor
}
*/


/*
//----------------------------------------------------------------------------------
char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode)
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
{ 
  unsigned error=0;
  unsigned int i;

  s_transstart();                   //transmission start
  switch(mode){                     //send command to sensor
    case TEMP	: error+=s_write_byte(MEASURE_TEMP); break;
    case HUMI	: error+=s_write_byte(MEASURE_HUMI); break;
    default     : break;	 
  }
  for (i=0;i<65535;i++) if(DATA==0) break; //wait until sensor has finished the measurement
  if(DATA) error+=1;                // or timeout (~2 sec.) is reached
  *(p_value)  =s_read_byte(ACK);    //read the first byte (MSB)
  *(p_value+1)=s_read_byte(ACK);    //read the second byte (LSB)
  *p_checksum =s_read_byte(noACK);  //read checksum
  Prints("MSB=");
    Puthexbyte(*p_value);
    Prints("\r\n");
    Prints("LSB=");
    Puthexbyte(*(p_value+1));
    Prints("\r\n");

    return error;
}
*/

//----------------------------------------------------------------------------------
char s_humi(uchar *p_value, uchar *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{ 
	
  uchar error=0;
  uint i;
  s_transstart();                   //transmission start
  error=s_write_byte(MEASURE_HUMI); //send messure huminity command to sensor
  for (i=0;i<65535;i++) if(DATA==0) break; //wait until sensor has finished the measurement
  if(DATA) error+=1;                // or timeout (~2 sec.) is reached
  *(p_value)  =s_read_byte(ACK);    //read the first byte  (MSB)
  *(p_value+1)=s_read_byte(ACK);    //read the second byte (LSB)
  *p_checksum=s_read_byte(noACK);   //read checksum (8-bit) 
//    Prints("\r\n");
//    Prints("humi=");
//    Puthexbyte(*p_value);
//    Puthexbyte(*(p_value+1));
//    Prints("\r\n"); 
    
  return error;                     //error=1 in case of no response form the sensor
}


//----------------------------------------------------------------------------------
char s_temp(uchar *p_value, uchar *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{ 
	unsigned int tt;
  unsigned char t;
  uchar error=0;
  uint i;
  s_transstart();                   //transmission start
  error=s_write_byte(MEASURE_TEMP); //send messure tempture command to sensor
  for (i=0;i<65535;i++) if(DATA==0) break; //wait until sensor has finished the measurement
  if(DATA) error+=1;                // or timeout (~2 sec.) is reached
  *(p_value)  =s_read_byte(ACK);    //read the first byte  (MSB)
  *(p_value+1)=s_read_byte(ACK);    //read the second byte (LSB)
  *p_checksum=s_read_byte(noACK);   //read checksum (8-bit) 
//    Prints("temp=");
//    Puthexbyte(*p_value);
//    Puthexbyte(*(p_value+1));
//    Prints("\r\n");
//    tt=*((unsigned int *)p_value);
//    tt=(tt/100-40);
//    t=(tt%100);
//    Puthexbyte(tt); 
//    Putchar('.');
//    Puthexbyte(t); 
//    Prints("\r\n");
    return error;                   //error=1 in case of no response form the sensor
}


//----------------------------------------------------------------------------------------
void calc_sth11(float *p_humidity ,float *p_temperature)
//----------------------------------------------------------------------------------------
// calculates temperature  and humidity [%RH] 
// input :  humi [Ticks] (12 bit) 
//          temp [Ticks] (14 bit)
// output:  humi [%RH]
//          temp 
{ const float C1=-4.0;               // for 12 Bit
  const float C2=+0.0405;            // for 12 Bit
  const float C3=-0.0000028;         // for 12 Bit
  const float T11=+0.01;             // for 14 Bit @ 5V
  const float T22=+0.00008;          // for 14 Bit @ 5V	

  float rh=*p_humidity;             // rh:      Humidity [Ticks] 12 Bit 
  float t=*p_temperature;           // t:       Temperature [Ticks] 14 Bit
  float rh_lin;                     // rh_lin:  Humidity linear
  float rh_true;                    // rh_true: Temperature compensated humidity
  float t_C;                        // t_C   :  Temperature 

  t_C=t*0.01 - 40;                  //calc. temperature from ticks to
   printf("temp:%f\n",t_C);
   Prints("\r\n");
  rh_lin=C3*rh*rh + C2*rh + C1;     //calc. humidity from ticks to [%RH]
  rh_true=(t_C-25)*(T11+T22*rh)+rh_lin;   //calc. temperature compensated humidity [%RH]
  if(rh_true>100)rh_true=100;       //cut if the value is outside of
  if(rh_true<0.1)rh_true=0.1;       //the physical possible range
   printf("%humi:%f\n",rh_true);
   Prints("\r\n");
  *p_temperature=t_C;               //return temperature 
  *p_humidity=rh_true;              //return humidity[%RH]
}


/*
//--------------------------------------------------------------------
float calc_dewpoint(float h,float t)
//--------------------------------------------------------------------
// calculates dew point
// input:   humidity [%RH], temperature
// output:  dew point 
{ float logEx,dew_point;
  logEx=0.66077+7.5*t/(237.3+t)+(log10(h)-2);
  dew_point = (logEx - 0.66077)*237.3/(0.66077+7.5-logEx);
  return dew_point;
}
*/

void main()
{ 

  value humi_val,temp_val;
 // float dew_point;
 
//  char temp,humi;
  uchar error,checksum;
//  uchar statusreg=0x01;
//  uchar status=0;
  float f =0.02;
  unsigned int i;
  for(i=0;i<1000;i++);
  InitialIO();
  InitialUart();
  //Prints("Initial is over\r\n");
  //s_connectionreset();

  while(1)                     //调试用程序,试验证明可对寄存器的读取操作;
   {                            //证明硬件电路没有问题;
     
//    error=0;
//    f=f*0.01 - 40;  
//    Putchar('a');
//f=f*0.01*f - 40*f*f;                //calc. temperature from ticks to 
  //rh_lin=C3*rh*rh + C2*rh + C1;     //calc. humidity from ticks to [%RH]
     //printf("temp:%f\n",f);
//    error+=s_softreset();
//    Prints("error=");
//    Puthexbyte(error);
//    Prints("\r\n");
//  error+= s_write_statusreg( &statusreg);
//   Prints("error=");
//   Puthexbyte(error);
//   Prints("\r\n");
//  error+= s_read_statusreg( &status,&checksum);
//   Prints("error=");
//   Puthexbyte(error);
//   Prints("\r\n");
     error+=s_humi((unsigned char*) &humi_val,&checksum);      //measure humidity
     error+=s_temp((unsigned char*) &temp_val,&checksum);      //measure temperature
  

     if(error!=0) s_connectionreset();         //in case of an error: connection reset
     else
     {
    	 

        humi_val.f=(float)humi_val.i;            //converts integer to float
        temp_val.f=(float)temp_val.i;            //converts integer to float
        calc_sth11(&humi_val.f,&temp_val.f);     //calculate humidity, temperature
        
      }    
    }
}

/*  s_connectionreset();
  while(1)
  { 
    error=0;
//  error+=s_measure((unsigned char*) &humi_val.i,&checksum,HUMI);  
    error+=s_measure((unsigned char*) &temp_val.i,&checksum,TEMP);  
//    error+=s_softreset();
//    Prints("error=");
//    Puthexbyte(error);
//    Prints("\r\n");
    if(error!=0) s_connectionreset();                 //in case of an error: connection reset
    else
    { 
      humi_val.f=(float)humi_val.i;                 //converts integer to float
      temp_val.f=(float)temp_val.i;                   //converts integer to float
      calc_sth11(&humi_val.f,&temp_val.f);            //calculate humidity, temperature
     // dew_point=calc_dewpoint(humi_val.f,temp_val.f); //calculate dew point
     // printf("temp:%5.1fC humi:%5.1f%% dew point:%5.1fC\n",temp_val.f,humi_val.f,dew_point);
    }
    //----------wait approx. 0.8s to avoid heating up SHTxx------------------------------      
   // for (i=0;i<40000;i++);     //(be sure that the compiler doesn't eliminate this line!)
    //-----------------------------------------------------------------------------------                       
  
 // }
}*/