tmphm_sht45.c

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/*
 * MT 22.12.2025
 *
 * Temp&hum 23 click  SHT45.pdf   https://download.mikroe.com/documents/datasheets/SHT45-AD1B-R2_datasheet.pdf
 *
 * I could have taken the library directly from https://github.com/MikroElektronika/mikrosdk_click_v2/blob/master/clicks/temphum23/lib_temphum23/src/temphum23.c
 * but there is a problem that I would need to pull in other modules.
 * Therefore going the route of direct reading from I2C
 *
 * geminy:
 * https://gemini.google.com/share/b64c25662edf
 */
 
#include "tmphm_sht45.h"
 
#ifdef SENSOR_SHT45
 
#include "i2c.h"
#include "utils/mydefs.h"
#include "mymems.h"
#include <stdio.h>
 
static uint16_t _tempHumAddr = 0x44;// - must be set via init 0x44; // or 0x45
static int8_t _isTempHumSensor = 0;
static int8_t _isOnOff = 0;     // dummy
 
tmphm_sht45_t _tmphm_sht45Data = { };
tmphm_sht45_t _bck_tmphm_sht45Data = {};    // backup
 
static HAL_StatusTypeDef tempHum_onOff(I2C_HandleTypeDef *hi2c, uint8_t onOff)
{
    HAL_StatusTypeDef status = I2C_IsDeviceReadyMT(hi2c, (_tempHumAddr << 1), 2, 2);    // real control
 
    if (status == HAL_OK)
        _isOnOff = onOff;
    _isTempHumSensor = (status == HAL_OK);
    return status;
}
 
int8_t tmphm_sht45_Is(I2C_HandleTypeDef *hi2c, int8_t tryInit)//
{
    if (!_isTempHumSensor && tryInit)
        tmphm_sht45_Init(hi2c);
    return _isTempHumSensor;
}
 
HAL_StatusTypeDef tmphm_sht45_IsOn(I2C_HandleTypeDef *hi2c, uint8_t *onOff)
{
    HAL_StatusTypeDef status = _isTempHumSensor ? HAL_OK : HAL_ERROR;
 
    if (status == HAL_OK)
        if (onOff != NULL)
            *onOff = _isOnOff;
    return status;
}
 
HAL_StatusTypeDef tmphm_sht45_On(I2C_HandleTypeDef *hi2c)
{
    HAL_StatusTypeDef status = tempHum_onOff(hi2c, 1);
 
    _tmphm_sht45Data.IsDataValid = 0;
    if (status == HAL_OK)
    {
        _memsMainBlock.Sens_TempHumStart++;
        mems_WriteMainBlock();
    }
    return status;
}
 
HAL_StatusTypeDef tmphm_sht45_Off(I2C_HandleTypeDef *hi2c)
{
    return tempHum_onOff(hi2c, 0);
}
 
 
HAL_StatusTypeDef tmphm_sht45_Init(I2C_HandleTypeDef *hi2c) //
{
    HAL_StatusTypeDef status = HAL_ERROR;
 
    /*
    for (_tempHumAddr = 0x44; _tempHumAddr <= 0x45; _tempHumAddr++) //
    {
        status = MY_I2C_IsDeviceReady(hi2c, _tempHumAddr << 1, 2, 2);   // first check
        _isTempHumSenzor = (status == HAL_OK);
        if (_isTempHumSenzor)
            break;
    }
    */
    status = I2C_IsDeviceReadyMT(hi2c, (_tempHumAddr << 1), 2, 2);
    _isTempHumSensor = (status == HAL_OK);
    return status;
}
 
uint8_t tempHum_CheckCrc(uint8_t *data, uint8_t len, uint8_t checksum) //
{
    uint8_t crc = 0xFF; // Initialization
    for (uint8_t i = 0; i < len; i++) {
        crc ^= data[i];
        for (uint8_t bit = 8; bit > 0; --bit) {
            if (crc & 0x80) {
                crc = (crc << 1) ^ 0x31;
            } else {
                crc = (crc << 1);
            }
        }
    }
    return (crc == checksum);
}
 
HAL_StatusTypeDef tmphm_sht45_Read(I2C_HandleTypeDef *hi2c) //
{
    uint8_t cmd = 0xFD; // High precision command
    uint8_t buffer[6];
    HAL_StatusTypeDef ret = HAL_ERROR;
 
    if (_isTempHumSensor) //
    {
        do //
        {
            if (!_isOnOff)
            {
                ret = HAL_TIMEOUT;
                break;
            }
            // 1. Send Command (Address 0x44 << 1 = 0x88)
            ret = HAL_I2C_Master_Transmit(hi2c, (_tempHumAddr << 1), &cmd, 1, 100);
            if (ret != HAL_OK)
                break;
 
            // 2. Wait for measurement (SHT45 takes ~8.2ms max)
            HAL_Delay(10);
 
            // 3. Read 6 bytes of data
            ret = HAL_I2C_Master_Receive(hi2c, (_tempHumAddr << 1), buffer, 6, 100);
            if (ret != HAL_OK)
                break;
 
            ret = HAL_ERROR;
            // 4. Validate CRC for Temperature (buffer[0,1] vs buffer[2])
            if (!tempHum_CheckCrc(&buffer[0], 2, buffer[2]))
                break;
 
            // 5. Validate CRC for Humidity (buffer[3,4] vs buffer[5])
            if (!tempHum_CheckCrc(&buffer[3], 2, buffer[5]))
                break;
 
            // 6. Convert Raw to Physical Values
            uint16_t t_raw = (buffer[0] << 8) | buffer[1];
            uint16_t rh_raw = (buffer[3] << 8) | buffer[4];
 
            _tmphm_sht45Data.Temperature = -45.0f + 175.0f * (float) t_raw / 65535.0f;
            _tmphm_sht45Data.Humidity = -6.0f + 125.0f * (float) rh_raw / 65535.0f;
 
            // Simple clipping for humidity (sensor can return slightly < 0 due to precision)
            if (_tmphm_sht45Data.Humidity < 0)
                _tmphm_sht45Data.Humidity = 0;
            if (_tmphm_sht45Data.Humidity > 100)
                _tmphm_sht45Data.Humidity = 100;
            ret = HAL_OK;
            _tmphm_sht45Data.IsDataValid = 1;
        } while (0);
    }
    return ret;
}
 
void tmphm_sht45_LogData(char* buf)
{
    if (buf != NULL)
        sprintf(buf, "|tempHum temp:" PRIf_02 " hum:" PRIf_02 " ", PRIf_02D(_tmphm_sht45Data.Temperature), PRIf_02D(_tmphm_sht45Data.Humidity));
 
}
 
#endif