?? sht11.c
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/*********************************************
SHT1X Humidity and Temperature Sensor
Pin 1 GND
Pin 2 Data (PB0)
Pin 3 Serial Clock (PB1)
Pin 4 VDD (2.4V to 5.5V)
*********************************************/
#include "REG2051.H"
#include <stdio.h>
#include <math.h>
#include <intrins.h>
// Declare your global variables here
typedef union
{ unsigned int i; float f;} value;
enum {TEMP,HUMI};
sbit SHT_DATA_IN = 0xB4;
sbit SHT_DATA_OUT = 0xB4;
sbit SHT_SCK = 0xB5;
#define noACK 0
#define ACK 1
//adr command r/w
#define STATUS_REG_W 0x06 //000 0011 0
#define STATUS_REG_R 0x07 //000 0011 1
#define MEASURE_TEMP 0x03 //000 0001 1
#define MEASURE_HUMI 0x05 //000 0010 1
#define RESET 0x1e //000 1111 0
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 TC1=+0.01; // for 14 Bit @ 5V
const float TC2=+0.00008; // for 14 Bit @ 5V
// Function Prototypes
char not_leap(void);
//SHT Functions
char SHT_WriteByte(unsigned char value);
char SHT_ReadByte(unsigned char ack);
void s_transstart(void);
void s_connectionreset(void);
char s_softreset(void);
char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode);
void calc_sth11(float *p_humidity ,float *p_temperature);
float calc_dewpoint(float h,float t);
void delay_ms(int t);
void delay_us(int t);
char s_write_statusreg(unsigned char *p_value);
char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum);
void main(void)
{
// Declare your local variables here
value humi_val, temp_val;
unsigned char error, checksum, status;
float dew_point;
//s_softreset();
s_connectionreset();
/*
while (1)
{
s_transstart(); //transmission start
error+=SHT_WriteByte(MEASURE_TEMP); //send command to sensor
for (i=0;i<65535;i++)
if(SHT_DATA_IN==0) break; //wait until sensor has finished the measurement
if(SHT_DATA_IN) error+=1; //or timeout (~2 sec.) is reached
MSB =SHT_ReadByte(ACK); //read the first byte (MSB)
LSB =SHT_ReadByte(ACK); //read the second byte (LSB)
checksum =SHT_ReadByte(noACK); //read checksum
//sprintf(lcd_buffer,"T= %u %u %u",MSB,LSB,checksum);
//lcd_gotoxy(0,1);
//lcd_puts(lcd_buffer);
delay_ms(500);
}
*/
while (1)
{
error=0;
// status = 0x04; // Heater On
status = 0x00; // Heater Off
s_write_statusreg(&status);
error+=s_measure((unsigned char*) &humi_val.i,&checksum,HUMI);
error+=s_measure((unsigned char*) &temp_val.i,&checksum,TEMP);
if(error!=0) s_connectionreset();
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
delay_ms(1000);
}
}
}
//----------------------------------------------------------------------------------
// writes a byte on the Sensibus and checks the acknowledge
//----------------------------------------------------------------------------------
char SHT_WriteByte( char value)
{
unsigned char i,error=0;
SHT_SCK=0;
for (i=0x80;i>0;i/=2) //shift bit for masking
{
if (i & value) SHT_DATA_OUT=1; //masking value with i , write to SENSI-BUS
else SHT_DATA_OUT=0;
delay_us(1);
SHT_SCK=1; //clk for SENSI-BUS
delay_us(1); //pulswith approx. 5 us
SHT_SCK=0;
}
SHT_DATA_OUT=0; //release DATA-line
SHT_SCK=1; //clk #9 for ack
error=SHT_DATA_IN; //check ack (DATA will be pulled down by SHT11)
delay_us(1);
SHT_SCK=0;
SHT_DATA_OUT=1;
return error; //error=1 in case of no acknowledge
}
//----------------------------------------------------------------------------------
// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1"
//----------------------------------------------------------------------------------
char SHT_ReadByte(unsigned char ack)
{
unsigned char i,val=0;
// SHT_DATA_OUT=1; //release DATA-line
for (i=0x80;i>0;i/=2) //shift bit for masking
{
delay_us(1);
SHT_SCK=1; //clk for SENSI-BUS
if (SHT_DATA_IN) val=(val | i); //read bit
delay_us(1);
SHT_SCK=0;
}
delay_us(1);
SHT_DATA_OUT=ack; //in case of "ack==1" pull down DATA-Line
SHT_SCK=1; //clk #9 for ack
delay_us(1); //pulswith approx. 5 us
SHT_SCK=0;
// SHT_DATA_OUT=1; //release DATA-line
return val;
}
//----------------------------------------------------------------------------------
// generates a transmission start
// _____ ________
// DATA: |_______|
// ___ ___
// SCK : ___| |___| |______
//----------------------------------------------------------------------------------
void s_transstart(void)
{
SHT_DATA_OUT=1;
SHT_SCK=0; //Initial state
delay_us(1);
SHT_SCK=1;
delay_us(1);
SHT_DATA_OUT=0;
delay_us(1);
SHT_SCK=0;
delay_us(2);
SHT_SCK=1;
delay_us(1);
SHT_DATA_OUT=1;
delay_us(1);
SHT_SCK=0;
}
//----------------------------------------------------------------------------------
// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
// _____________________________________________________ ________
// DATA: |_______|
// _ _ _ _ _ _ _ _ _ ___ ___
// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |______
//----------------------------------------------------------------------------------
void s_connectionreset(void)
{
unsigned char i;
SHT_DATA_OUT=1; SHT_SCK=0; //Initial state
for(i=0;i<9;i++) //9 SCK cycles
{
SHT_SCK=1;
delay_us(1);
SHT_SCK=0;
delay_us(1);
}
s_transstart(); //transmission start
}
//----------------------------------------------------------------------------------
// resets the sensor by a softreset
//----------------------------------------------------------------------------------
char s_softreset(void)
{
unsigned char error=0;
s_connectionreset(); //reset communication
error+=SHT_WriteByte(RESET); //send RESET-command to sensor
return error; //error=1 in case of no response form the sensor
}
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
//----------------------------------------------------------------------------------
char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode)
{
unsigned error=0;
unsigned int i;
s_transstart(); //transmission start
switch(mode){ //send command to sensor
case TEMP : error+=SHT_WriteByte(MEASURE_TEMP); break;
case HUMI : error+=SHT_WriteByte(MEASURE_HUMI); break;
default : break;
}
for (i=0;i<65535;i++) if(SHT_DATA_IN==0) break; //wait until sensor has finished the measurement
if(SHT_DATA_IN) error+=1; // or timeout (~2 sec.) is reached
*(p_value) =SHT_ReadByte(noACK); //read the first byte (MSB)
*(p_value+1) =SHT_ReadByte(noACK); //read the second byte (LSB)
*p_checksum =SHT_ReadByte(ACK); //read checksum
return error;
}
//----------------------------------------------------------------------------------------
// calculates temperature [癈] and humidity [%RH]
// input : humi [Ticks] (12 bit)
// temp [Ticks] (14 bit)
// output: humi [%RH]
// temp [癈]
//----------------------------------------------------------------------------------------
void calc_sth11(float *p_humidity ,float *p_temperature)
{
float rh_lin; // rh_lin: Humidity linear
float rh_true; // rh_true: Temperature compensated humidity
float t_C; // t_C : Temperature [癈]
t_C=*p_temperature*0.01 - 40; //calc. temperature from ticks to [癈]
rh_lin=C3*(*p_humidity)*(*p_humidity) + C2*(*p_humidity) + C1; //calc. humidity from ticks to [%RH]
rh_true=(t_C-25)*(TC1+TC2*(*p_humidity))+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
*p_temperature=t_C; //return temperature [癈]
*p_humidity=rh_true; //return humidity[%RH]
}
//--------------------------------------------------------------------
// calculates dew point
// input: humidity [%RH], temperature [癈]
// output: dew point [癈]
//--------------------------------------------------------------------
float calc_dewpoint(float h,float t)
{
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;
}
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
//----------------------------------------------------------------------------------
char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum)
{
unsigned char error=0;
s_transstart(); //transmission start
error=SHT_WriteByte(STATUS_REG_R); //send command to sensor
*p_value=SHT_ReadByte(ACK); //read status register (8-bit)
*p_checksum=SHT_ReadByte(noACK); //read checksum (8-bit)
return error; //error=1 in case of no response form the sensor
}
//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
//----------------------------------------------------------------------------------
char s_write_statusreg(unsigned char *p_value)
{
unsigned char error=0;
s_transstart(); //transmission start
error+=SHT_WriteByte(STATUS_REG_W);//send command to sensor
error+=SHT_WriteByte(*p_value); //send value of status register
return error; //error>=1 in case of no response form the sensor
}
void delay_us(int t)
{int i;
for(i=0;i<t;i++)
{
_nop_();
}
}
void delay_ms(int t)
{int i;
for(i=0;i<t;i++)
delay_us(1000);
}
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