twr_sht20.c

#include <twr_sht20.h>
 
#define _TWR_SHT20_DELAY_RUN 20
#define _TWR_SHT20_DELAY_INITIALIZATION 20
#define _TWR_SHT20_DELAY_MEASUREMENT_RH 50
#define _TWR_SHT20_DELAY_MEASUREMENT_T 100
 
static void _twr_sht20_task_interval(void *param);
 
static void _twr_sht20_task_measure(void *param);
 
static bool _twr_sht20_write(twr_sht20_t *self, const uint8_t data);
 
// TODO SHT20 has only one fixed address so it is no necessary to pass it as parameter
 
void twr_sht20_init(twr_sht20_t *self, twr_i2c_channel_t i2c_channel, uint8_t i2c_address)
{
    memset(self, 0, sizeof(*self));
 
    self->_i2c_channel = i2c_channel;
    self->_i2c_address = i2c_address;
 
    self->_task_id_interval = twr_scheduler_register(_twr_sht20_task_interval, self, TWR_TICK_INFINITY);
    self->_task_id_measure = twr_scheduler_register(_twr_sht20_task_measure, self, _TWR_SHT20_DELAY_RUN);
 
    self->_tick_ready = _TWR_SHT20_DELAY_RUN;
 
    twr_i2c_init(self->_i2c_channel, TWR_I2C_SPEED_400_KHZ);
}
 
void twr_sht20_deinit(twr_sht20_t *self)
{
    _twr_sht20_write(self, 0xfe);
    twr_scheduler_unregister(self->_task_id_interval);
    twr_scheduler_unregister(self->_task_id_measure);
}
 
void twr_sht20_set_event_handler(twr_sht20_t *self, void (*event_handler)(twr_sht20_t *, twr_sht20_event_t, void *), void *event_param)
{
    self->_event_handler = event_handler;
    self->_event_param = event_param;
}
 
void twr_sht20_set_update_interval(twr_sht20_t *self, twr_tick_t interval)
{
    self->_update_interval = interval;
 
    if (self->_update_interval == TWR_TICK_INFINITY)
    {
        twr_scheduler_plan_absolute(self->_task_id_interval, TWR_TICK_INFINITY);
    }
    else
    {
        twr_scheduler_plan_relative(self->_task_id_interval, self->_update_interval);
 
        twr_sht20_measure(self);
    }
}
 
bool twr_sht20_measure(twr_sht20_t *self)
{
    if (self->_measurement_active)
    {
        return false;
    }
 
    self->_measurement_active = true;
 
    twr_scheduler_plan_absolute(self->_task_id_measure, self->_tick_ready);
 
    return true;
}
 
bool twr_sht20_get_humidity_raw(twr_sht20_t *self, uint16_t *raw)
{
    if (!self->_humidity_valid)
    {
        return false;
    }
 
    *raw = self->_reg_humidity;
 
    return true;
}
 
bool twr_sht20_get_humidity_percentage(twr_sht20_t *self, float *percentage)
{
    uint16_t raw;
 
    if (!twr_sht20_get_humidity_raw(self, &raw))
    {
        return false;
    }
 
    *percentage = -6.f + 125.f * (float) raw / 65536.f;
 
    if (*percentage >= 100.f)
    {
        *percentage = 100.f;
    }
    else if (*percentage <= 0.f)
    {
        *percentage = 0.f;
    }
 
    return true;
}
 
bool twr_sht20_get_temperature_raw(twr_sht20_t *self, uint16_t *raw)
{
    if (!self->_temperature_valid)
    {
        return false;
    }
 
    *raw = self->_reg_temperature;
 
    return true;
}
 
bool twr_sht20_get_temperature_celsius(twr_sht20_t *self, float *celsius)
{
    uint16_t raw;
 
    if (!twr_sht20_get_temperature_raw(self, &raw))
    {
        return false;
    }
 
    *celsius = -46.85f + 175.72f * (float) raw / 65536.f;
 
    return true;
}
 
bool twr_sht20_get_temperature_fahrenheit(twr_sht20_t *self, float *fahrenheit)
{
    float celsius;
 
    if (!twr_sht20_get_temperature_celsius(self, &celsius))
    {
        return false;
    }
 
    *fahrenheit = celsius * 1.8f + 32.f;
 
    return true;
}
 
bool twr_sht20_get_temperature_kelvin(twr_sht20_t *self, float *kelvin)
{
    float celsius;
 
    if (!twr_sht20_get_temperature_celsius(self, &celsius))
    {
        return false;
    }
 
    *kelvin = celsius + 273.15f;
 
    if (*kelvin < 0.f)
    {
        *kelvin = 0.f;
    }
 
    return true;
}
 
static void _twr_sht20_task_interval(void *param)
{
    twr_sht20_t *self = param;
 
    twr_sht20_measure(self);
 
    twr_scheduler_plan_current_relative(self->_update_interval);
}
 
static void _twr_sht20_task_measure(void *param)
{
    twr_sht20_t *self = param;
 
start:
 
    switch (self->_state)
    {
        case TWR_SHT20_STATE_ERROR:
        {
            self->_humidity_valid = false;
            self->_temperature_valid = false;
 
            self->_measurement_active = false;
 
            if (self->_event_handler != NULL)
            {
                self->_event_handler(self, TWR_SHT20_EVENT_ERROR, self->_event_param);
            }
 
            self->_state = TWR_SHT20_STATE_INITIALIZE;
 
            return;
        }
        case TWR_SHT20_STATE_INITIALIZE:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            if (!_twr_sht20_write(self, 0xfe))
            {
                goto start;
            }
 
            self->_state = TWR_SHT20_STATE_MEASURE_RH;
 
            self->_tick_ready = twr_tick_get() + _TWR_SHT20_DELAY_INITIALIZATION;
 
            if (self->_measurement_active)
            {
                twr_scheduler_plan_current_absolute(self->_tick_ready);
            }
 
            return;
        }
        case TWR_SHT20_STATE_MEASURE_RH:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            if (!_twr_sht20_write(self, 0xf5))
            {
                goto start;
            }
 
            self->_state = TWR_SHT20_STATE_READ_RH;
 
            twr_scheduler_plan_current_from_now(_TWR_SHT20_DELAY_MEASUREMENT_RH);
 
            return;
        }
        case TWR_SHT20_STATE_READ_RH:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            uint8_t buffer[2];
 
            twr_i2c_transfer_t transfer;
 
            transfer.device_address = self->_i2c_address;
            transfer.buffer = buffer;
            transfer.length = sizeof(buffer);
 
            if (!twr_i2c_read(self->_i2c_channel, &transfer))
            {
                goto start;
            }
 
            self->_reg_humidity = buffer[0] << 8 | buffer[1];
            self->_reg_humidity &= ~0x3;
 
            self->_humidity_valid = true;
 
            self->_state = TWR_SHT20_STATE_MEASURE_T;
 
            goto start;
        }
        case TWR_SHT20_STATE_MEASURE_T:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            if (!_twr_sht20_write(self, 0xf3))
            {
                goto start;
            }
 
            self->_state = TWR_SHT20_STATE_READ_T;
 
            twr_scheduler_plan_current_from_now(_TWR_SHT20_DELAY_MEASUREMENT_T);
 
            return;
        }
        case TWR_SHT20_STATE_READ_T:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            uint8_t buffer[2];
 
            twr_i2c_transfer_t transfer;
 
            transfer.device_address = self->_i2c_address;
            transfer.buffer = buffer;
            transfer.length = sizeof(buffer);
 
            if (!twr_i2c_read(self->_i2c_channel, &transfer))
            {
                goto start;
            }
 
            self->_reg_temperature = buffer[0] << 8 | buffer[1];
            self->_reg_temperature &= ~0x3;
 
            self->_temperature_valid = true;
 
            self->_state = TWR_SHT20_STATE_UPDATE;
 
            goto start;
        }
        case TWR_SHT20_STATE_UPDATE:
        {
            self->_measurement_active = false;
 
            if (self->_event_handler != NULL)
            {
                self->_event_handler(self, TWR_SHT20_EVENT_UPDATE, self->_event_param);
            }
 
            self->_state = TWR_SHT20_STATE_MEASURE_RH;
 
            return;
        }
        default:
        {
            self->_state = TWR_SHT20_STATE_ERROR;
 
            goto start;
        }
    }
}
 
static bool _twr_sht20_write(twr_sht20_t *self, const uint8_t data)
{
    twr_i2c_transfer_t transfer;
 
    transfer.device_address = self->_i2c_address;
    transfer.buffer = (void *) &data;
    transfer.length = sizeof(data);
 
    return twr_i2c_write(self->_i2c_channel, &transfer);
}