HTS221 can't return humidity values below 32%
Hello,
I got the problem, that the humidity sensor can't return values below 32.
My code is the same like in the documentation (only in C): https://www.st.com/content/ccc/resource/technical/document/technical_note/group0/82/97/c8/ab/c6/da/41/ed/DM00208001/files/DM00208001.pdf/jcr:content/translations/en.DM00208001.pdf
/* read coefficients */
int _H0_rH_x2, _H1_rH_x2, _H0_T0_OUT, _H1_T0_OUT;
_H0_rH_x2 = i2c_read_register(address,0x30);
_H1_rH_x2 = i2c_read_register(address,0x31);
_H0_T0_OUT = i2c_read_register(address,0x37) <<8;
_H0_T0_OUT |= i2c_read_register(address,0x36);
_H1_T0_OUT = i2c_read_register(address,0x3b) <<8;
_H1_T0_OUT |= i2c_read_register(address,0x3a);
/* calculate humidity */
unsigned conversation_status = 0;
int H_OUT;
int t_H0_rH, t_H1_rH;
int humidity_ = 0;
unsigned humidity;
if(!i2c_humidity_sensor_status(address)){
H_OUT = (unsigned int)i2c_read_register(address,0x29) <<8;
H_OUT |= (unsigned int)i2c_read_register(address,0x28);
printf("H_OUT 0x29 : %d\n", i2c_read_register(address,0x29));
printf("H_OUT 0x28 : %d\n", i2c_read_register(address,0x28));
t_H0_rH = _H0_rH_x2>>1; //divided by 2
t_H1_rH = _H1_rH_x2>>1; //divided by 2
humidity_ = ((int)(H_OUT - _H0_T0_OUT)) * ((int)(t_H1_rH - t_H0_rH));
humidity_ = (int)(humidity_ / (int)(_H1_T0_OUT - _H0_T0_OUT) + t_H0_rH);
printf("H_OUT: %d \nt_H0_rH: %d \nt_H1_rH: %d \n_H0_T0_OUT: %d \n_H1_T0_OUT: %d \n", H_OUT,t_H0_rH,t_H1_rH,_H0_T0_OUT, _H1_T0_OUT );
printf("humidity: %d\n", humidity_);
humidity = (unsigned)humidity_;
if (humidity > 100){
humidity = 100;
}
return humidity;
} else {
printf("No data available!\n\n");
return 101;
}My output is this:
H_OUT 0x29 : 254
H_OUT 0x28 : 102
H_OUT: 65126
H0_rH: 32
H1_rH: 70
_H0_T0_OUT: 65529
_H1_T0_OUT: 52304
humidity: 33
humidity: 33 %
H_OUT 0x29 : 255
H_OUT 0x28 : 20
H_OUT: 65300
H0_rH: 32
H1_rH: 70
_H0_T0_OUT: 65529
_H1_T0_OUT: 52304
humidity: 32
humidity: 32 %
H_OUT 0x29 : 0
H_OUT 0x28 : 34
H_OUT: 34
H0_rH: 32
H1_rH: 70
_H0_T0_OUT: 65529
_H1_T0_OUT: 52304
humidity: 220
humidity: 100 %
H_OUT 0x29 : 0
H_OUT 0x28 : 87
H_OUT: 87
H0_rH: 32
H1_rH: 70
_H0_T0_OUT: 65529
_H1_T0_OUT: 52304
humidity: 220
humidity: 100 %
H_OUT 0x29 : 1
H_OUT 0x28 : 104
H_OUT: 360
H0_rH: 32
H1_rH: 70
H0_T0_OUT: 65529
H1_T0_OUT: 52304
humidity: 219
humidity: 100 %
H_OUT 0x29 : 2
H_OUT 0x28 : 7
H_OUT: 519
H0_rH: 32
H1_rH: 70
_H0_T0_OUT: 65529
_H1_T0_OUT: 52304
humidity: 218
humidity: 100 %
The register value from H_OUT drops from 6500 to ~ 0.
I see the same on my oscilloscope, how is the possible ?