HTS221 H0_T0_OUT and H1_T0_OUT, H0_RH and H1_RH returns same value

[CureSaba]

In HTS221 sensor I have issue that H0_T0_OUT and H1_T0_OUT, H0_RH and H1_RH value is same like below

T0_degC float 20.5
T1_degC float 52.5
T0_OUT int16_t 1028
T1_OUT int16_t 0
H0_RH float 29.5
H1_RH float 29.5
H0_T0_OUT int16_t 0xf7f7 (hex)
H1_T0_OUT int16_t 0xf7f7 (hex)

This is my code
Init function

uint8_t HTS221_Init(HTS221 *hts221, I2C_HandleTypeDef *hi2c) {
	hts221->hi2c = hi2c;
	uint8_t data[2];
	if (HTS221_ReadRegister(hts221, HTS221_WHO_AM_I, data, 1) != HAL_OK) {
		return 1; // Error reading WHO_AM_I register
	}
	if (data[0] != HTS221_WHO_AM_I_VALUE) {
		return 2; // WHO_AM_I value does not match expected value
	}
	// Read calibration data
	if (HTS221_ReadRegister(hts221, CALIB_0, data, 2) != HAL_OK) {
		return 3; // Error reading calibration data
	}
	hts221->H0_RH = (float) (data[0]) / 2.0f; // H0_rH_x2
	hts221->H1_RH = (float) (data[1]) / 2.0f; // H1_rH_x2
	if (HTS221_ReadRegister(hts221, CALIB_2, data, 2) != HAL_OK) {
		return 4; // Error reading temperature calibration data
	}
	uint16_t T0_degC_x8 = (data[0]);
	uint16_t T1_degC_x8 = (data[1]);
	if (HTS221_ReadRegister(hts221, CALIB_5, data, 1) != HAL_OK) {
		return 5; // Error reading T1/T0 msb
	}
	hts221->T0_degC = (float) (T0_degC_x8 | ((data[0] & 0b0011) << 8)) / 8.0f; // T0_degC_x8
	hts221->T1_degC = (float) (T1_degC_x8 | (((data[0] & 0b1100) >> 2) << 8))
			/ 8.0f; // T1_degC_x8
	if (HTS221_ReadRegister(hts221, CALIB_6, data, 2) != HAL_OK) {
		return 6; // Error reading H0_T0_OUT
	}
	hts221->H0_T0_OUT = (int16_t) ((data[1] << 8) | data[0]); // H0_T0_OUT_H and H0_T0_OUT_L
	if (HTS221_ReadRegister(hts221, CALIB_A, data, 2) != HAL_OK) {
		return 7; // Error reading H1_T0_OUT
	}
	hts221->H1_T0_OUT = (int16_t) ((data[1] << 8) | data[0]); // H1_T0_OUT_H and H1_T0_OUT_L
	if (HTS221_ReadRegister(hts221, CALIB_C, data, 2) != HAL_OK) {
		return 8; // Error reading T0_OUT
	}
	hts221->T0_OUT = (int16_t) ((data[1] << 8) | data[0]); // T0_OUT_H and T0_OUT_L
	if (HTS221_ReadRegister(hts221, CALIB_E, data, 2) != HAL_OK) {
		return 9; // Error reading T1_OUT
	}
	hts221->T1_OUT = (int16_t) ((data[1] << 8) | data[0]); // T1_OUT_H and T1_OUT_L

	return 0; // Initialization successful
}

 Header file

/*
 * HTS221.h
 *
 *  Created by CureSaba on 2025/08/21.
 *  This header file defines the interface for the HTS221 humidity and temperature sensor.
 *  It includes necessary definitions, register addresses, and a structure for sensor data.
*/

#ifndef HTS221_H
#define HTS221_H
#include "stm32l0xx_hal.h" // Include the HAL library for STM32L0xx

// Define the I2C address for the HTS221 sensor(P.20 of HTS221 datasheet)
#define HTS221_I2C_SAD (0b1011111<<1) // 7-bit address for HTS221
#define HTS221_WHO_AM_I 0x0F // WHO_AM_I register address
#define HTS221_WHO_AM_I_VALUE 0xBC // Expected value for WHO_AM_I register

#define AV_CONF 0x10 // Average configuration register address
#define CTRL_REG1 0x20
#define CTRL_REG2 0x21
#define CTRL_REG3 0x22
#define STATUS_REG 0x27
#define HUMIDITY_OUT_L 0x28
#define HUMIDITY_OUT_H 0x29
#define TEMP_OUT_L 0x2A
#define TEMP_OUT_H 0x2B
// Calibration registers(P.26 of HTS221 datasheet)
#define CALIB_0 0x30 // H0_rH_x2
#define CALIB_1 0x31 // H1_rH_x2
#define CALIB_2 0x32 // T0_degC_x8
#define CALIB_3 0x33 // T1_degC_x8
#define CALIB_5 0x35 // T1/T0 msb
#define CALIB_6 0x36 // H0_T0_OUT_L
#define CALIB_7 0x37 // H0_T0_OUT_H
#define CALIB_A 0x3A // H1_T0_OUT_L
#define CALIB_B 0x3B // H1_T0_OUT_H
#define CALIB_C 0x3C // T0_OUT_L
#define CALIB_D 0x3D // T0_OUT_H
#define CALIB_E 0x3E // T1_OUT_L
#define CALIB_F 0x3F // T1_OUT_H

typedef struct {
    I2C_HandleTypeDef *hi2c; // Pointer to the I2C handle

    // Temperature calibration data
    float T0_degC;
    float T1_degC;
    int16_t T0_OUT;
    int16_t T1_OUT;
    // Humidity calibration data
    float H0_RH;
    float H1_RH;
    int16_t H0_T0_OUT;
    int16_t H1_T0_OUT;

    float humidity;
    float temperature;
} HTS221;

// Initialization function for HTS221
uint8_t HTS221_Init(HTS221 *hts221, I2C_HandleTypeDef *hi2c);

// Low-level read and write functions for HTS221
HAL_StatusTypeDef HTS221_ReadRegister(HTS221 *hts221, uint8_t reg, uint8_t *data, uint16_t size);
HAL_StatusTypeDef HTS221_WriteRegister(HTS221 *hts221, uint8_t reg, uint8_t *data, uint16_t size);

// Function to read humidity and temperature data from HTS221
HAL_StatusTypeDef HTS221_ReadTemperature(HTS221 *hts221);
HAL_StatusTypeDef HTS221_ReadHumidity(HTS221 *hts221);

#endif // HTS221_H

[Federica Bossi]

Hi @CureSaba ,

Based on the header and initialization code, the register addresses and data processing appear correct. However, identical values for H0_T0_OUT and H1_T0_OUT often indicate an issue with reading the calibration registers. I recommend verifying the I2C read function to ensure it correctly reads and updates the data buffer for each register. Adding small delays between consecutive reads may also help. Additionally, testing with another sensor or using an I2C scanner or logic analyzer to read the calibration registers directly can help isolate whether the issue is hardware or software related.