embedded-sgp30

This is a platform agnostic Rust driver the SGP30 digital gas sensor using the embedded-hal traits.

The device

The SGP30 is a gas sensor for indoor air quality applications such as air purifiers, demand-controlled ventilation or IoT.

It provides detailed information about the air quality, such as TVOC and CO₂eq. It also gives access to the raw measurement values of ethanol and H₂.

It is addressed via an I²C interface and has a low power consumption.

Here are its measument ranges:

ppm: parts per million. 1 ppm = 1000 ppb (parts per billion)

For more details on the accuracy and the resolution, take a look at the datasheet link below.

Documentation:

• Datasheet
• C source code from the manufacturer

Features

• Initialize an air quality measure.
• Perform an air quality measure (returns the TVOC and CO₂eq values).
• Get the baseline values of the baseline correction algorithm.
• Set the baseline values of the baseline correction algorithm.
• Set the humidity to provide the on-chip humidity compensation algorithm with an absolute humidity value from an external humidity sensor like the sht3x.
• Do a sofware set.
• Perform a raw signals measure (returns the Ethanol and H₂ values).
• Include a no floating-point variant for systems without fpu.

Usage

To use this driver, import what you need from this crate and an embedded-hal implentation, then instatiate the device.

use embedded_hal::delay::DelayNs;
use embedded_sgp30::{Sgp30, I2C_ADDRESS};
use linux_embedded_hal as hal;

fn main() -> Result<(), embedded_sgp30::Error<hal::I2CError>> {
    // Create the I2C device from the chosen embedded-hal implementation,
    // in this case linux-embedded-hal
    let i2c = match hal::I2cdev::new("/dev/i2c-1") {
        Err(err) => {
            eprintln!("Could not create I2C device: {}", err);
            std::process::exit(1);
        }
        Ok(i2c) => i2c,
    };

    // Create the sensor and configure its repeatability
    let mut sensor = Sgp30::new(i2c, I2C_ADDRESS, hal::Delay {})?;
    sensor.initialize_air_quality_measure()?;

    // Perform an air quality measurement every second
    let mut delay = hal::Delay {};
    for i in 0..30 {
        delay.delay_ms(1000);
        let measurement = sensor.measure_air_quality()?;

        // Only print the measurement after the startup time of 15s
        if i > 15 {
            println!(
                "CO₂eq: {} ppm, TVOC: {} ppb",
                measurement.co2, measurement.tvoc
            );
        }
    }
    Ok(())
}

Correct usage of baseline get & set

The saving and restore of baseline values should not be done at any random time.

If starting the sensor without restoring a previous baseline, the sensor will try to determine a new baseline. For that, the adjustement algorithm has to run for 12 hours. Therefore you should not save the baseline values during these 12 hours. Reading out the baseline prior to that should be avoided unless a valid baseline has first been restored.

After these 12 hours, or if a baseline has been restored at startup, the baseline should be stored approximately once per hour. If the sensor is off for some time, the stored baseline values can be stored for a maximum of 7 days. If the sensor is off for a longer time, the stored baseline should be erased and the process started again from the beginning, so you should wait once again 12 hours before storing the new baseline.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.