bme280_rs/

blocking.rs

// Copyright Claudio Mattera 2022-2026.
//
// Distributed under the MIT License or the Apache 2.0 License at your option.
// See the accompanying files LICENSE-MIT.txt and LICENSE-APACHE-2.0.txt, or
// online at
// https://opensource.org/licenses/MIT
// https://opensource.org/licenses/Apache-2.0

//! Data types and functions for BME280 sensor interface

use embedded_hal::delay::DelayNs;
use embedded_hal::i2c::I2c;

use crate::calibration;
use crate::constants::BME280_COMMAND_SOFTRESET;
use crate::constants::BME280_REGISTER_CHIPID;
use crate::constants::BME280_REGISTER_CONFIG;
use crate::constants::BME280_REGISTER_CONTROL;
use crate::constants::BME280_REGISTER_CONTROLHUMID;
use crate::constants::BME280_REGISTER_HUMIDDATA;
use crate::constants::BME280_REGISTER_PRESSUREDATA;
use crate::constants::BME280_REGISTER_SOFTRESET;
use crate::constants::BME280_REGISTER_STATUS;
use crate::constants::BME280_REGISTER_TEMPDATA;
use crate::constants::DEFAULT_ADDRESS;
use crate::constants::MODE_SLEEP;
use crate::constants::SKIPPED_HUMIDITY_OUTPUT;
use crate::constants::SKIPPED_PRESSURE_OUTPUT;
use crate::constants::SKIPPED_TEMPERATURE_OUTPUT;
use crate::macros::debug;
use crate::macros::warn;
use crate::sample::humidity_from_number;
use crate::sample::pressure_from_pascal;
use crate::sample::temperature_from_celsius;
use crate::sample::Humidity;
use crate::sample::Pressure;
use crate::sample::RawSample;
use crate::sample::Sample;
use crate::sample::Temperature;
use crate::CalibrationData;
use crate::Configuration;
use crate::Status;

/// Interface to BME280 sensor over I²C
///
/// ```no_run
/// # use embedded_hal_mock::eh1::delay::NoopDelay as DelayMock;
/// # use embedded_hal_mock::eh1::i2c::Mock as I2cMock;
/// # use embedded_hal::i2c::ErrorKind;
/// use bme280_rs::{Bme280, Configuration, Oversampling, SensorMode};
/// # let i2c = I2cMock::new(&[]);
/// # let delay = DelayMock;
///
/// let mut bme280 = Bme280::new(i2c, delay);
///
/// bme280.init()?;
///
/// let configuration = Configuration::default()
///     .with_temperature_oversampling(Oversampling::Oversample1)
///     .with_pressure_oversampling(Oversampling::Oversample1)
///     .with_humidity_oversampling(Oversampling::Oversample1)
///     .with_sensor_mode(SensorMode::Normal);
/// bme280.set_sampling_configuration(configuration)?;
///
/// if let Some(temperature) = bme280.read_temperature()? {
///     println!("Temperature: {:?}", temperature);
/// } else {
///     println!("Temperature reading was disabled");
/// }
/// # Ok::<(), ErrorKind>(())
/// ```
pub struct Bme280<I2c, Delay> {
    /// I²C device
    i2c: I2c,

    /// I²C address
    address: u8,

    /// Delay function
    delay: Delay,

    /// Calibration coefficients
    coefficients: CalibrationData,

    /// Sensor configuration
    configuration: Configuration,
}

impl<I2C, D> Bme280<I2C, D>
where
    I2C: I2c,
    D: DelayNs,
{
    /// Create a new sensor using an I²C interface and a delay function using
    /// the sensor's default address [`DEFAULT_ADDRESS`])
    pub fn new(i2c: I2C, delay: D) -> Self {
        Self::new_with_address(i2c, DEFAULT_ADDRESS, delay)
    }

    /// Release the I²C interface
    pub fn release(self) -> I2C {
        self.i2c
    }

    /// Create a new sensor using an I²C interface and a delay function
    pub fn new_with_address(i2c: I2C, address: u8, delay: D) -> Self {
        Self::new_with_coefficients(i2c, address, delay, CalibrationData::default())
    }

    /// Create a new sensor with specific calibration coefficients
    fn new_with_coefficients(
        i2c: I2C,
        address: u8,
        delay: D,
        coefficients: CalibrationData,
    ) -> Self {
        debug!("Creating new BME280 device at address 0x{:x}", address);
        Self {
            i2c,
            address,
            delay,
            coefficients,
            configuration: Configuration::default(),
        }
    }

    /// Initialize the sensor
    ///
    /// Send a soft-reset signal, obtain the calibration coefficients, and set
    /// default sampling configuration.
    ///
    /// Note that the default sampling configuration disables measurement of
    /// temperature, pressure and humidity.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn init(&mut self) -> Result<(), I2C::Error> {
        debug!("Sending soft-reset signal");
        self.write_u8(BME280_REGISTER_SOFTRESET, BME280_COMMAND_SOFTRESET)?;

        debug!("Waiting 10 ms");
        self.delay.delay_ms(10);

        while self.status()?.is_calibrating() {
            debug!("Calibration not complete, waiting 10 ms");
            self.delay.delay_ms(10);
        }

        debug!("Reading coefficients");
        self.read_calibration_coefficients()?;

        debug!("Set sampling");
        let configuration = Configuration::default();
        self.set_sampling_configuration(configuration)?;

        debug!("Waiting 100 ms");
        self.delay.delay_ms(100);

        Ok(())
    }

    /// Obtain the chip id
    ///
    /// The chip id is always [`crate::constants::CHIP_ID`], so this function
    /// can be used to validate that communication with the chip works fine.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn chip_id(&mut self) -> Result<u8, I2C::Error> {
        debug!("Read chip id");
        let chip_id = self.read_u8(BME280_REGISTER_CHIPID)?;

        Ok(chip_id)
    }

    /// Obtain the chip status
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn status(&mut self) -> Result<Status, I2C::Error> {
        debug!("Read chip status");
        let status = self.read_u8(BME280_REGISTER_STATUS)?.into();

        Ok(status)
    }

    /// Set the sampling configuration
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn set_sampling_configuration(
        &mut self,
        configuration: Configuration,
    ) -> Result<(), I2C::Error> {
        self.configuration = configuration;

        let (config, ctrl_meas, ctrl_hum) = self.configuration.to_lowlevel_configuration();

        // making sure sensor is in sleep mode before setting configuration
        // as it otherwise may be ignored
        self.write_u8(BME280_REGISTER_CONTROL, MODE_SLEEP)?;

        // you must make sure to also set REGISTER_CONTROL after setting the
        // CONTROLHUMID register, otherwise the values won't be applied (see
        // DS 5.4.3)
        self.write_u8(BME280_REGISTER_CONTROLHUMID, ctrl_hum.into())?;
        self.write_u8(BME280_REGISTER_CONFIG, config.into())?;
        self.write_u8(BME280_REGISTER_CONTROL, ctrl_meas.into())?;

        Ok(())
    }

    /// Take a forced measurement
    ///
    /// When the chip is set to work in forced mode, it goes back to sleep
    /// after every measurement.
    /// It must be set again to forced mode in order to force a new
    /// measurement.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn take_forced_measurement(&mut self) -> Result<bool, I2C::Error> {
        if self.configuration.is_forced() {
            debug!("Forcing taking a measurement");

            let (_config, ctrl_meas, _ctrl_hum) = self.configuration.to_lowlevel_configuration();
            self.write_u8(BME280_REGISTER_CONTROL, ctrl_meas.into())?;

            for _ in 0..10 {
                if !self.status()?.is_measuring() {
                    break;
                }

                debug!("Measuring not complete, waiting 10 ms");
                self.delay.delay_ms(10);
            }

            Ok(true)
        } else {
            Ok(false)
        }
    }

    /// Read a raw sample from sensor
    ///
    /// Raw sample must be converted to human-readable quantities using
    /// compensation formulas from the data sheet.
    fn read_raw_sample(&mut self) -> Result<RawSample, I2C::Error> {
        let buffer: [u8; 1] = [BME280_REGISTER_PRESSUREDATA];
        let mut buf: [u8; 8] = [0; 8];
        self.i2c.write_read(self.address, &buffer, &mut buf)?;

        // msb [7:0] = p[19:12]
        // lsb [7:0] = p[11:4]
        // xlsb[7:4] = p[3:0]
        let adc_p: u32 =
            (u32::from(buf[0]) << 12) | (u32::from(buf[1]) << 4) | (u32::from(buf[2]) >> 4);
        // msb [7:0] = t[19:12]
        // lsb [7:0] = t[11:4]
        // xlsb[7:4] = t[3:0]
        let adc_t: u32 =
            (u32::from(buf[3]) << 12) | (u32::from(buf[4]) << 4) | (u32::from(buf[5]) >> 4);
        // msb [7:0] = h[15:8]
        // lsb [7:0] = h[7:0]
        let adc_h: u16 = (u16::from(buf[6]) << 8) | u16::from(buf[7]);

        Ok(RawSample {
            adc_t: if adc_t == SKIPPED_TEMPERATURE_OUTPUT {
                None
            } else {
                Some(adc_t)
            },
            adc_p: if adc_p == SKIPPED_PRESSURE_OUTPUT {
                None
            } else {
                Some(adc_p)
            },
            adc_h: if adc_h == SKIPPED_HUMIDITY_OUTPUT {
                None
            } else {
                Some(adc_h)
            },
        })
    }

    /// Read a sample of temperature, pressure and humidity
    ///
    /// Measures that are disabled in the sampling configuration have value
    /// `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_sample(&mut self) -> Result<Sample, I2C::Error> {
        let RawSample {
            adc_t,
            adc_p,
            adc_h,
        } = self.read_raw_sample()?;

        if let Some(adc_t) = adc_t {
            let t_fine = self.coefficients.compensate_temperature(adc_t);
            let t = Some(Self::temperature_fine_to_temperature(t_fine));
            let p = adc_p.map(|adc_p| self.coefficients.compensate_pressure(adc_p, t_fine));
            let h = adc_h.map(|adc_h| self.coefficients.compensate_humidity(adc_h, t_fine));

            let temperature = t;

            #[allow(clippy::cast_precision_loss)] // Acceptable precision loss
            let pressure = p.map(|p| p as f32 / 256.0);
            let pressure = pressure.map(pressure_from_pascal);
            #[allow(clippy::cast_precision_loss)] // Acceptable precision loss
            let humidity = h.map(|h| h as f32 / 1024.0);
            let humidity = humidity.map(humidity_from_number);

            Ok(Sample {
                temperature,
                pressure,
                humidity,
            })
        } else {
            warn!("Temperature measurement is disabled");

            Ok(Sample::default())
        }
    }

    /// Compute raw temperature from human-readable temperature
    fn temperature_fine_to_temperature(t_fine: i32) -> Temperature {
        let t = (t_fine * 5 + 128) >> 8;

        #[allow(clippy::cast_precision_loss)] // Acceptable precision loss
        let t = t as f32;

        temperature_from_celsius(t / 100.0)
    }

    /// Read a sample of temperature
    ///
    /// If temperature is disabled in the sampling configuration, return `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_temperature(&mut self) -> Result<Option<Temperature>, I2C::Error> {
        if let Some(t_fine) = self.read_temperature_fine()? {
            Ok(Some(Self::temperature_fine_to_temperature(t_fine)))
        } else {
            Ok(None)
        }
    }

    /// Read temperature from sensor
    fn read_temperature_fine(&mut self) -> Result<Option<i32>, I2C::Error> {
        let adc_t = self.read_raw_temperature()?;
        let t_fine = adc_t.map(|adc_t| self.coefficients.compensate_temperature(adc_t));
        Ok(t_fine)
    }

    /// Read raw temperature from sensor
    ///
    /// Raw temperature must be converted to human-readable temperature using
    /// compensation formulas from the data sheet.
    fn read_raw_temperature(&mut self) -> Result<Option<u32>, I2C::Error> {
        let adc_t = self.read_u24(BME280_REGISTER_TEMPDATA)?;

        if adc_t == SKIPPED_TEMPERATURE_OUTPUT {
            Ok(None)
        } else {
            Ok(Some(adc_t))
        }
    }

    /// Read a sample of pressure
    ///
    /// The temperature value, necessary to compute the compensated pressure
    /// value, is also read from the sensor.
    ///
    /// If pressure is disabled in the sampling configuration, return `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_pressure(&mut self) -> Result<Option<Pressure>, I2C::Error> {
        if let Some(t_fine) = self.read_temperature_fine()? {
            self.read_pressure_with_temperature_fine(t_fine)
        } else {
            warn!("Pressure measurement is disabled");
            Ok(None)
        }
    }

    /// Read a sample of pressure with a user-specified temperature value
    ///
    /// Unlike in [`Self::read_pressure()`], this function does not take the
    /// temperature from the sensor, so it can be used if the temperature
    /// is already known.
    ///
    /// If pressure is disabled in the sampling configuration, return `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_pressure_with_temperature(
        &mut self,
        temperature: f32,
    ) -> Result<Option<Pressure>, I2C::Error> {
        #[allow(clippy::cast_possible_truncation)] // Acceptable truncation
        let t = (temperature * 100.0) as i32;
        let t_fine = ((t << 8) - 128) / 5;
        self.read_pressure_with_temperature_fine(t_fine)
    }

    /// Read pressure from sensor using specific temperature reference
    fn read_pressure_with_temperature_fine(
        &mut self,
        t_fine: i32,
    ) -> Result<Option<Pressure>, I2C::Error> {
        let adc_p = self.read_raw_pressure()?;
        let p = adc_p.map(|adc_p| {
            let p = self.coefficients.compensate_pressure(adc_p, t_fine);

            #[allow(clippy::cast_precision_loss)] // Acceptable precision loss
            let p = p as f32;

            pressure_from_pascal(p / 256.0)
        });
        Ok(p)
    }

    /// Read raw pressure from sensor
    ///
    /// Raw pressure must be converted to human-readable pressure using
    /// compensation formulas from the data sheet.
    fn read_raw_pressure(&mut self) -> Result<Option<u32>, I2C::Error> {
        let adc_p = self.read_u24(BME280_REGISTER_PRESSUREDATA)?;

        if adc_p == SKIPPED_PRESSURE_OUTPUT {
            Ok(None)
        } else {
            Ok(Some(adc_p))
        }
    }

    /// Read a sample of humidity
    ///
    /// The temperature value, necessary to compute the compensated pressure
    /// value, is also read from the sensor.
    ///
    /// If humidity is disabled in the sampling configuration, return `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_humidity(&mut self) -> Result<Option<Humidity>, I2C::Error> {
        if let Some(t_fine) = self.read_temperature_fine()? {
            self.read_humidity_with_temperature_fine(t_fine)
        } else {
            warn!("Humidity measurement is disabled");
            Ok(None)
        }
    }

    /// Read a sample of humidity with a user-specified temperature value
    ///
    /// Unlike in [`Self::read_humidity()`], this function does not take the
    /// temperature from the sensor, so it can be used if the temperature
    /// is already known.
    ///
    /// If humidity is disabled in the sampling configuration, return `None`.
    ///
    /// # Errors
    ///
    /// Return an error if it cannot communicate with the sensor.
    pub fn read_humidity_with_temperature(
        &mut self,
        temperature: f32,
    ) -> Result<Option<Humidity>, I2C::Error> {
        #[allow(clippy::cast_possible_truncation)] // Acceptable truncation
        let t = (temperature * 100.0) as i32;
        let t_fine = ((t << 8) - 128) / 5;
        self.read_humidity_with_temperature_fine(t_fine)
    }

    /// Read humidity from sensor using specific reference temperature
    fn read_humidity_with_temperature_fine(
        &mut self,
        t_fine: i32,
    ) -> Result<Option<Humidity>, I2C::Error> {
        let adc_h = self.read_raw_humidity()?;
        let h = adc_h.map(|adc_h| {
            let h = self.coefficients.compensate_humidity(adc_h, t_fine);

            #[allow(clippy::cast_precision_loss)] // Acceptable precision loss
            let h = h as f32;

            humidity_from_number(h / 1024.0)
        });
        Ok(h)
    }

    /// Read raw humidity from sensor
    ///
    /// Raw humidity must be converted to human-readable humidity using
    /// compensation formulas from the data sheet.
    fn read_raw_humidity(&mut self) -> Result<Option<u16>, I2C::Error> {
        let adc_h = self.read_u16(BME280_REGISTER_HUMIDDATA)?;

        if adc_h == SKIPPED_HUMIDITY_OUTPUT {
            Ok(None)
        } else {
            Ok(Some(adc_h))
        }
    }

    /// Read calibration coefficients from sensor
    fn read_calibration_coefficients(&mut self) -> Result<(), I2C::Error> {
        let buffer: [u8; 1] = [calibration::FIRST_REGISTER];

        let mut out: [u8; calibration::TOTAL_LENGTH] = [0; calibration::TOTAL_LENGTH];
        self.i2c.write_read(
            self.address,
            &buffer,
            &mut out[0..calibration::FIRST_LENGTH],
        )?;

        let buffer: [u8; 1] = [calibration::SECOND_REGISTER];
        self.i2c.write_read(
            self.address,
            &buffer,
            &mut out[calibration::FIRST_LENGTH..calibration::TOTAL_LENGTH],
        )?;

        self.coefficients = (&out).into();

        Ok(())
    }

    /// Write an unsigned byte to an I²C register
    fn write_u8(&mut self, register: u8, value: u8) -> Result<(), I2C::Error> {
        let buffer: [u8; 2] = [register, value];
        self.i2c.write(self.address, &buffer)?;
        Ok(())
    }

    /// Write an unsigned byte from an I²C register
    fn read_u8(&mut self, register: u8) -> Result<u8, I2C::Error> {
        let buffer: [u8; 1] = [register];
        let mut output_buffer: [u8; 1] = [0];
        self.i2c
            .write_read(self.address, &buffer, &mut output_buffer)?;
        Ok(output_buffer[0])
    }

    /// Write two unsigned bytes to an I²C register
    fn read_u16(&mut self, register: u8) -> Result<u16, I2C::Error> {
        let buffer: [u8; 1] = [register];
        let mut output_buffer: [u8; 2] = [0, 0];
        self.i2c
            .write_read(self.address, &buffer, &mut output_buffer)?;
        Ok((u16::from(output_buffer[0]) << 8) | u16::from(output_buffer[1]))
    }

    /// Write three unsigned bytes to an I²C register
    fn read_u24(&mut self, register: u8) -> Result<u32, I2C::Error> {
        let buffer: [u8; 1] = [register];
        let mut output_buffer: [u8; 3] = [0, 0, 0];
        self.i2c
            .write_read(self.address, &buffer, &mut output_buffer)?;
        Ok((u32::from(output_buffer[0]) << 12)
            | (u32::from(output_buffer[1]) << 4)
            | (u32::from(output_buffer[2]) >> 4))
    }
}

#[cfg(test)]
mod tests {
    #![allow(clippy::panic_in_result_fn)]

    use alloc::vec;

    use embedded_hal::i2c::ErrorKind;

    use embedded_hal_mock::eh1::delay::NoopDelay as DelayMock;
    use embedded_hal_mock::eh1::i2c::Mock as I2cMock;
    use embedded_hal_mock::eh1::i2c::Transaction as I2cTransaction;

    use crate::calibration::TEST_CALIBRATION_DATA;
    use crate::constants::CHIP_ID;

    use super::*;

    #[test]
    fn test_init() -> Result<(), ErrorKind> {
        let expectations = [
            // Reset sensor
            I2cTransaction::write(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_SOFTRESET, BME280_COMMAND_SOFTRESET],
            ),
            // Wait for calibration
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_STATUS],
                vec![0b0000_0001],
            ),
            // Wait for calibration
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_STATUS],
                vec![0b0000_0000],
            ),
            // Read coefficients
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![calibration::FIRST_REGISTER],
                vec![0; 26],
            ),
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![calibration::SECOND_REGISTER],
                vec![0; 7],
            ),
            // Configure sensor
            I2cTransaction::write(DEFAULT_ADDRESS, vec![BME280_REGISTER_CONTROL, MODE_SLEEP]),
            I2cTransaction::write(DEFAULT_ADDRESS, vec![BME280_REGISTER_CONTROLHUMID, 0]),
            I2cTransaction::write(DEFAULT_ADDRESS, vec![BME280_REGISTER_CONFIG, 0]),
            I2cTransaction::write(DEFAULT_ADDRESS, vec![BME280_REGISTER_CONTROL, 0]),
        ];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new(i2c, DelayMock);

        bme280.init()?;

        bme280.release().done();

        Ok(())
    }

    #[test]
    fn test_chip_id() -> Result<(), ErrorKind> {
        let expectations = [I2cTransaction::write_read(
            DEFAULT_ADDRESS,
            vec![BME280_REGISTER_CHIPID],
            vec![CHIP_ID],
        )];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new(i2c, DelayMock);

        let chip_id = bme280.chip_id()?;

        assert_eq!(chip_id, CHIP_ID);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_chip_status() -> Result<(), ErrorKind> {
        let expectations = [I2cTransaction::write_read(
            DEFAULT_ADDRESS,
            vec![BME280_REGISTER_STATUS],
            vec![0x00],
        )];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new(i2c, DelayMock);

        let status = bme280.status()?;

        assert!(!status.is_measuring());
        assert!(!status.is_calibrating());

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_chip_status_measuring() -> Result<(), ErrorKind> {
        let expectations = [I2cTransaction::write_read(
            DEFAULT_ADDRESS,
            vec![BME280_REGISTER_STATUS],
            vec![0b0000_0100],
        )];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new(i2c, DelayMock);

        let status = bme280.status()?;

        assert!(status.is_measuring());
        assert!(!status.is_calibrating());

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_temperature_disabled() -> Result<(), ErrorKind> {
        let expectations = [I2cTransaction::write_read(
            DEFAULT_ADDRESS,
            vec![BME280_REGISTER_TEMPDATA],
            vec![0x80, 0x00, 0x00],
        )];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = None;

        let temperature = bme280.read_temperature()?;

        assert_eq!(temperature, expected);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_temperature() -> Result<(), ErrorKind> {
        let expectations = [I2cTransaction::write_read(
            DEFAULT_ADDRESS,
            vec![BME280_REGISTER_TEMPDATA],
            vec![0x84, 0x47, 0x00],
        )];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = Some(temperature_from_celsius(27.33));

        let temperature = bme280.read_temperature()?;

        assert_eq!(temperature, expected);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_pressure_disabled() -> Result<(), ErrorKind> {
        let expectations = [
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_TEMPDATA],
                vec![0x84, 0x47, 0x00],
            ),
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_PRESSUREDATA],
                vec![0x80, 0x00, 0x00],
            ),
        ];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = None;

        let pressure = bme280.read_pressure()?;

        assert_eq!(pressure, expected);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_pressure() -> Result<(), ErrorKind> {
        let expectations = [
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_TEMPDATA],
                vec![0x84, 0x47, 0x00],
            ),
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_PRESSUREDATA],
                vec![0x4f, 0x50, 0x00],
            ),
        ];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = Some(pressure_from_pascal(101_233.016));

        let pressure = bme280.read_pressure()?;

        assert_eq!(pressure, expected);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_humidity_disabled() -> Result<(), ErrorKind> {
        let expectations = [
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_TEMPDATA],
                vec![0x84, 0x47, 0x00],
            ),
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_HUMIDDATA],
                vec![0x80, 0x00],
            ),
        ];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = None;

        let humidity = bme280.read_humidity()?;

        assert_eq!(humidity, expected);

        bme280.release().done();
        Ok(())
    }

    #[test]
    fn test_read_humidity() -> Result<(), ErrorKind> {
        let expectations = [
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_TEMPDATA],
                vec![0x84, 0x47, 0x00],
            ),
            I2cTransaction::write_read(
                DEFAULT_ADDRESS,
                vec![BME280_REGISTER_HUMIDDATA],
                vec![0x60, 0x02],
            ),
        ];
        let i2c = I2cMock::new(&expectations);

        let mut bme280 = Bme280::new_with_coefficients(
            i2c,
            DEFAULT_ADDRESS,
            DelayMock,
            TEST_CALIBRATION_DATA.clone(),
        );

        let expected = Some(humidity_from_number(34.854_492));

        let humidity = bme280.read_humidity()?;

        assert_eq!(humidity, expected);

        bme280.release().done();
        Ok(())
    }
}