rw_sht.c

盛世瑞恩公司SHT90温湿度传感器 测量温湿度的源代码 C语言 51单片机

/*****************************************************************************************************
* Filename:      SHT91_Sample_code
* File func:     the command to write/read the sht_sensor
* File description: the file is included in "main.c" to fulfill the read_write command
* Prozessor:     80C51 Family
* Compiler:      Keil    Wave IDE
* Author:        qcx
* Version:     v1.1
*********************************************************************************************************/
//-------------------------------------------------------------------------
#include "math.h"
#include "intrins.h"
#include "sht_demo.h"
//--------------------------------------------------------------------------
char s_write_byte(unsigned char value)
//--------------------------------------------------------------------------
//writes a byte on the Sensibu and checks the acknowledge
{
    unsigned char i,error=0;
    for (i=0x80;i>0;i/=2)       //shift bit for masking
    {
       if(i & value) DATA=1;    //masking value with i,write every bit of value
       else DATA=0;             //to SENSI-BUS
       SCK=1;                   //clk for SENSI-BUS
       _nop_ ();                //The frequancy of the clk should be less than
       _nop_ ();                //4k Hz
       _nop_ ();
       SCK=0;
    }
    DATA=1;
    SCK=1;
    error=DATA;
    SCK=0;
    return error;               //error=1 in case of no acknowledge
}

//-----------------------------------------------------------------------
char s_read_byte(unsigned char ack)
//-----------------------------------------------------------------------
//func: read a byte from Sens-bus and gives an acknowledge
{
    unsigned char i,val=0;
    for(i=0x80;i>0;i/=2)
    {
        SCK=1;
        if (DATA) val=(val | i);
        SCK=0;
    }
    DATA= !ack;              //in case of "ack==1" pull down DATA-Line
    SCK=1;
    _nop_();
    _nop_();    _nop_();
    DATA=1;
    return val;
}

//-------------------------------------------------------------------------
void s_transstart(void)
//-------------------------------------------------------------------------
//func: generate a transmission start signal
{
    DATA=1;
    SCK=0;             //initial state
    _nop_();
    SCK=1;
    _nop_();
    DATA=0;
    _nop_();
    SCK=0;
    _nop_();
    _nop_();
    _nop_();
    SCK=1;
    _nop_();
    DATA=1;
    _nop_();
    SCK=0;       // refer to the pdf from SENSIRION(start transmission)
}

//------------------------------------------------------------------------------
void s_connectionreset(void)
//------------------------------------------------------------------------------
//func: communication reset:DATA-line and at least 9 sck cycles followed by transstart
{
    unsigned char i;
    DATA=1;
    SCK=0;
    for(i=0;i<9;i++)
    {
        SCK=1;
        SCK=0;
    }
    s_transstart();
}

//--------------------------------------------------------------------------------
char s_softreset(void)
//--------------------------------------------------------------------------------
//func: reset 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;               //sensor=1 in case of no response from sensor
}

//-----------------------------------------------------------------------------------
char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum)
//-----------------------------------------------------------------------------------
//func: read the status register with checksum (8 bit)
{
    unsigned char error=0;
    s_transstart();                     //transmission start
    error=s_write_byte(STATUS_REG_R);   //send command to sensor
    *p_value=s_read_byte(ACK);          //read status register(8 bit)
    *p_checksum=s_read_byte(noACK);     //read checksum (8 bit)
    return error;                       //error=1 in case of no response from sensor
}

//----------------------------------------------------------------------------------------
char s_write_statusreg(unsigned char *p_value)
//----------------------------------------------------------------------------------------
//func: writes the status register with checksum(8 bit)
{
    unsigned char error=0;
    s_transstart();                     //transmission start
    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 from sensor
}

//-----------------------------------------------------------------------------------------
char s_measure(unsigned char *p_value,unsigned char *p_checksum,unsigned char mode)
//-----------------------------------------------------------------------------------------
//func: make a measurement(temperature or humity) with checksum
{
    unsigned char error=0;
    unsigned int  i;
    s_transstart();                           //start transmission
    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;
    if(DATA==1)  error+=1;
    *(p_value)=s_read_byte(ACK);      //read the first byte
    *(p_value+1) = s_read_byte(ACK);  //read the second byte
    *p_checksum = s_read_byte(noACK); //read checksum
    return error;
}

//-----------------------------------------------------------------------------------------------
void calc_sth(float *p_humidity,float *p_temperature)
//-----------------------------------------------------------------------------------------------
//func: calculates temperature and humidity
{
    const float C1=-4.0;
    const float C2=0.0405;
    const float C3=-0.0000028;
    const float T1=0.01;
    const float T2=0.00008;
    float rh=*p_humidity;
    float t=*p_temperature;
    float rh_lin;
    float rh_ture;
    float t_C;

    t_C=t*0.01 - 40;
    rh_lin=C3*rh*rh + C2*rh + C1;
    rh_ture=(t_C-25)*(T1+T2*rh)+rh_lin;
    if(rh_ture > 100) rh_ture=100;
    if(rh_ture < 0.1) rh_ture=0.1;

    *p_temperature=t_C;
    *p_humidity=rh_ture;
}

//--------------------------------------------------------------------------------------------------
float calc_dewpoint(float h,float t)
//----------------------------------------------------------------------------------------------------
//func: calculates the dewpoint
//input: humidity[%RH] , temperature[C]
//output: dew point
{
    float k,dew_point;
    k = (log10(h)-2)/0.4343 + (17.62*t)/(243.12+t);
    dew_point = 243.12 * k/(17.62-k);
    return dew_point;
}