/home/daqweb/fgddaq/c8051/Devices/Humidity_sensor.c File Reference

#include "../mscbemb.h"
#include "../Protocols/SHT7x_protocol.h"
#include "Humidity_sensor.h"

Functions
void	HumiSensor_Init (int humsen)
unsigned char	HumidSensor_Cmd (unsigned int *rhumidity, unsigned int *rtemperature, float *humidity, float *temperature, unsigned char *OrigFCS, unsigned char *DeviceFCS, int humsen)
signed char	SHT7x_Measure (unsigned int *DataToSend, unsigned char flag, unsigned char *FCSoriginator, unsigned char *FCSclient, int humsen)
void	SHT7x_Correction (float *p_humidity, float *p_temperature)
unsigned char	ReverseByte (unsigned char dataBeReversed)

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Function Documentation

unsigned char HumidSensor_Cmd	(	unsigned int *	rhumidity,
		unsigned int *	rtemperature,
		float *	humidity,
		float *	temperature,
		unsigned char *	OrigFCS,
		unsigned char *	DeviceFCS,
		int	humsen
	)

                                                                                                 {
        
        float         xdata temp_humi, temp_tempe;
        unsigned char xdata TempStatus,HumiStatus;
        unsigned int  xdata rtemp,rhumi;
        unsigned char xdata temp_FCSOrig,temp_FCSDevice;
        
        TempStatus = SHT7x_Measure(&rtemp, TEMP, &temp_FCSOrig, &temp_FCSDevice, humsen); //measure temperature
        HumiStatus = SHT7x_Measure(&rhumi, HUMI, &temp_FCSOrig, &temp_FCSDevice, humsen); //measure humidity
        
        *DeviceFCS = temp_FCSDevice;
        *OrigFCS = temp_FCSOrig;
        *rtemperature = rtemp;
        *rhumidity = rhumi;

  temp_humi  = (float) rhumi;   
  temp_tempe = (float) rtemp;
  SHT7x_Correction(&temp_humi,&temp_tempe);                     //calculate humidity, temperature
  *humidity = temp_humi;
  *temperature = temp_tempe;                                                            

        if((TempStatus == ERROR) || (HumiStatus == ERROR)){ 
                SHT7x_ConnectionReset(humsen); //in case of an error: connection reset
                // delay_ms(800);
                return ERROR;
        } 

        //wait approx. 0.8s to avoid heating up SHTxx
  //delay_ms(800);
        return DONE;
}

void HumiSensor_Init

(

int

humsen

)

                                {
        
        SHT7x_Init(humsen);
}

unsigned char ReverseByte

(

unsigned char

dataBeReversed

)

                                                        {

        unsigned char i,j,temp = 0;
        
        for ( i=0x80,j=7;i>=0x10;i/=2,j-=2 )
                        temp |= ((dataBeReversed & i) >> j);            
        
        for ( i=0x08,j=1;i>=0x01;i/=2,j+=2 )
                        temp |= ((dataBeReversed & i) << j);
        return temp;
}

void SHT7x_Correction	(	float *	p_humidity,
		float *	p_temperature
	)

{ 
        // Assuming VDD to be 3.5V but the actual voltage is 3.3V
        *p_temperature = (*p_temperature * D2) + D1 ;   
        *p_humidity = (*p_humidity) * (*p_humidity * C3) + *p_humidity * C2 + C1;       
        
        *p_humidity=(*p_temperature - 25)*(T1+ *p_humidity * T2)+ *p_humidity; //calc. Temperature compensated humidity [%RH]

        if(*p_humidity > 100)
                *p_humidity = 100;                  // Cut if the value is outside of
        
        if(*p_humidity <0.1)
                *p_humidity = 0.1;        // the physical possible range

}

signed char SHT7x_Measure	(	unsigned int *	DataToSend,
		unsigned char	flag,
		unsigned char *	FCSoriginator,
		unsigned char *	FCSclient,
		int	humsen
	)

{
        unsigned char xdata check_flag, status = DONE;
        unsigned char xdata FCSdevice, FCSorig, MSBdata, LSBdata;
        unsigned int  xdata measurements=0;
        unsigned long xdata SHT_time =0, temp_check=0;

        
        SHT7x_TransStart(humsen);                                                //transmission start
        
        switch(flag) {                                                           //send command to sensor
                case TEMP: 
                        status = SHT7x_WriteByte(MEASURE_TEMP, humsen); 
                        check_flag = MEASURE_TEMP;
                        break;
                
                case HUMI : 
                        status = SHT7x_WriteByte(MEASURE_HUMI, humsen); //if device does not ack, returns error
                        check_flag = MEASURE_HUMI;
                        break;
                
                default : 
                        break;
        }
        
        SHT_time = uptime();

        do {
                if(humsen==1) {
                        if(SHT7x_DATA1 == 0) {
                                temp_check = 1; 
                                break; //wait until sensor has finished the measurement
                        }
                }
#ifdef MORETHANONEHUM
                else if(humsen==2) {
                        if(SHT7x_DATA2 == 0) {
                                temp_check = 1; 
                                break; //wait until sensor has finished the measurement
                        }                       
                }
#endif
        }while ((uptime() - SHT_time) < SHT_TIME);
        

        if(temp_check == 0){ 
                SHT7x_ConnectionReset(humsen);
                return ERROR;                     // timeout is reached
        }

        //14bit temperature measurements
        //12bit humidity measurements
        MSBdata         = SHT7x_ReadByte(ACK, humsen);            //read the first byte (MSB)
        LSBdata         = SHT7x_ReadByte(ACK, humsen);      //read the second byte (LSB)
        FCSdevice = SHT7x_ReadByte(ACK, humsen);      //read the last byte (checksum)
        FCSdevice = ReverseByte (FCSdevice);
        
        //Calculate originator's side write FCS
  FCSorig = SHT7x_FCS_Step(LSBdata
          , SHT7x_FCS_Step(MSBdata
          , SHT7x_FCS_Step(check_flag
          , 0x00)));    

        *FCSclient = FCSdevice;
        *FCSoriginator = FCSorig;

        // Checking the checksum
        if (FCSdevice != FCSorig) {
                SHT7x_ConnectionReset(humsen);
                return ERROR;
  }

        measurements = (MSBdata <<8) | (LSBdata);

        if(flag == TEMP)
                measurements &= 0x3fff;
        else
                measurements &= 0x0fff;
        
        *DataToSend =  measurements;
        return status;     
}

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