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« on: September 16, 2010, 12:19:06 PM » |
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#include "lpc214x.h"
#include "sht71.h" อยากได้ไฟล์นี้ครับ
#include "delay.h"
#include "math.h"
// DATA = P0.27
// SCK = P0.26
//MYDEF'S
#define IODIR IODIR1
#define IOSET IOSET1
#define IOCLR IOCLR1
#define SCK 0x04000000
#define SCK_HIGH IOSET1 = 0x04000000;
#define SCK_LOW IOCLR1 = 0x04000000;
#define DATA 0x08000000
#define DATA_HIGH IOSET1 = 0x08000000;
#define DATA_LOW IOCLR1 = 0x08000000;
//MYDEF'S END
typedef union
{
unsigned int i;
float f;
}value;
enum { TEMPERATURE, HUMIDITY};
#define noACK 0
#define ACK 1
//adr command r/w
#define STATUS_REG_W 0x06 //0000 0110
#define STATUS_REG_R 0x07 //0000 0111
#define MEASURE_TEMP 0x03 //0000 0011
#define MEASURE_HUMI 0x05 //0000 0101
#define RESET 0x1e //0001 1110
char sht71_write_command(unsigned char command)
{
unsigned char i, err=0;
for (i=0x80; i>0; i/=2) //shift bit for masking
{
if (i & command)
DATA_HIGH //masking value with i , write to SENSI-BUS
else
DATA_LOW
SCK_HIGH //clk for SENSI-BUS
nop();
nop();
nop();; //pulswith approx. 5 us
SCK_LOW
}
DATA_HIGH //release DATA-line
IODIR &= ~(DATA); //define DATA line as input
SCK_HIGH //clk #9 for ack
//check ack (DATA will be pulled down by SHT11)
if(IOSET & DATA)
err = 1;
else
err = 0;
IODIR |= DATA; //define DATA line as output
SCK_LOW
return err;
}
char sht71_read_value(unsigned char ack)
{
unsigned char i,val=0;
DATA_HIGH //release DATA-line
IODIR &= ~(DATA); //define DATA line as input
for (i=0x80; i>0 ; i/=2) //shift bit for masking
{
SCK_HIGH //clk for SENSI-BUS
if (IOSET & DATA)
val=(val | i); //read bit
SCK_LOW;
}
IODIR = DATA; //define DATA line as ouput
if(!ack)
DATA_HIGH
else
DATA_LOW
SCK_HIGH //clk #9 for ack
nop();
nop();
nop(); //pulswith approx. 5 us
SCK_LOW
DATA_HIGH //release DATA-line
return val;
}
void sht71_transmission_start(void)
{
DATA_HIGH
SCK_LOW //Initial state
nop();
SCK_HIGH
nop();
DATA_LOW
nop();
SCK_LOW
nop();nop();nop();
SCK_HIGH
nop();
DATA_HIGH
nop();
SCK_LOW
}
void sht71_connection_reset(void)
{
unsigned char i;
DATA_HIGH
SCK_LOW //Initial state
for(i=0; i<9; i++) //9 SCK cycles
{
SCK_HIGH
SCK_LOW
}
sht71_transmission_start(); //transmission start
}
char sht71_soft_reset(void)
{
unsigned char err=0;
sht71_connection_reset(); //reset communication
err = sht71_write_command(RESET); //send RESET-command to sensor
return err; //error=1 in case of no response form the sensor
}
char sht71_read_status_register(unsigned char *p_value, unsigned char *p_checksum)
{
unsigned char err=0;
sht71_transmission_start(); //transmission start
err = sht71_write_command(STATUS_REG_R); //send command to sensor
*p_value = sht71_read_value(ACK); //read status register (8-bit)
*p_checksum = sht71_read_value(noACK); //read checksum (8-bit)
return err; //error=1 in case of no response form the sensor
}
char sht71_write_status_register(unsigned char *p_value)
{
unsigned char err=0;
sht71_transmission_start(); //transmission start
err += sht71_write_command(STATUS_REG_W);//send command to sensor
err += sht71_write_command(*p_value); //send value of status register
return err; //error>=1 in case of no response form the sensor
}
char sht71_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode)
{
unsigned err=0;
unsigned int i;
sht71_transmission_start(); //transmission start
switch(mode)
{ //send command to sensor
case TEMPERATURE : err += sht71_write_command(MEASURE_TEMP); break;
case HUMIDITY : err += sht71_write_command(MEASURE_HUMI); break;
default : break;
}
IODIR &= ~(DATA); //define DATA line as input
for (i=0;i<65535;i++)
if(!(IOSET & DATA))
break; //wait until sensor has finished the measurement
if(IOSET & DATA)
err+=1; // or timeout (~2 sec.) is reached
IODIR |= DATA; //define DATA line as input
*(p_value) = sht71_read_value(ACK); //read the first byte (MSB)
*(p_value+1)= sht71_read_value(ACK); //read the second byte (LSB)
*p_checksum = sht71_read_value(noACK); //read checksum
return err;
}
void sht71_calc_humidity(float *p_humidity ,float *p_temperature)
{
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 T1=0.01; // for 14 Bit @ 5V
const float T2=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 [C]
t_C = t * 0.01 - 40; //calc. Temperature from ticks to [C]
rh_lin=C3*rh*rh + C2*rh + C1; //calc. Humidity from ticks to [%RH]
rh_true=(t_C-25)*(T1+T2*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
*p_temperature = t_C; //return temperature [ C]
*p_humidity=rh_true; //return humidity[%RH]
}
void sht71_calc_temperature(float *p_temperature)
{
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 T1=0.01; // for 14 Bit @ 5V
const float T2=0.00008; // for 14 Bit @ 5V
float t=*p_temperature; // t: Temperature [Ticks] 14 Bit
float t_C; // t_C : Temperature [C]
t_C = t * 0.01 - 40; //calc. Temperature from ticks to [C]
*p_temperature = t_C; //return temperature [ C]
}
void sht71_init(void)
{
IODIR1 |= SCK;
IODIR1 |= DATA;
sht71_connection_reset();
}
//----------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!)
//-----------------------------------------------------------------------------------
float sht71_get_humidity()
{
value humi_val,temp_val;
unsigned char err,checksum;
err=0;
//measure humidity
err+=sht71_measure((unsigned char*) &humi_val.i,&checksum,HUMIDITY);
//measure temperature
err+=sht71_measure((unsigned char*) &temp_val.i,&checksum,TEMPERATURE);
if(err!=0)
{
//in case of an error: connection reset
sht71_connection_reset();
return -1;
}
else
{
//converts integer to float
humi_val.f=(float)humi_val.i;
temp_val.f=(float)temp_val.i;
//calculate humidity, temperature
sht71_calc_humidity(&humi_val.f, &temp_val.f);
return humi_val.f;
}
}
float sht71_get_temperature()
{
value temp_val;
unsigned char err, checksum;
err=0;
//measure temperature
err+=sht71_measure((unsigned char*) &temp_val.i,&checksum, TEMPERATURE);
if(err!=0)
{
sht71_connection_reset(); //in case of an error: connection reset
return (err * (-1));
}
else
{
//converts integer to float
temp_val.f=(float)temp_val.i;
//calculate temperature
sht71_calc_temperature(&temp_val.f);
return temp_val.f;
}
return 0; //DEBUG
}
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