Crate sgp4x 

Platform agnostic Rust driver for Sensirion SGP41 device with gas, temperature and humidity sensors based on the embedded-hal traits.

Sensirion SGP41

Sensirion SGP41 is a low-power accurate gas sensor for air quality application. The sensor has different sampling rates to optimize power-consumption per application bases as well as ability save and set the baseline for faster start-up accuracy. The sensor uses I²C interface and measures TVOC (Total Volatile Organic Compounds) and NOx (Nitrogen Oxides).

Datasheet: https://www.sensirion.com/file/datasheet_sgp41

Usage

Instantiating

Import this crate and an embedded_hal implementation, then instantiate the device:

use linux_embedded_hal as hal;

use hal::{Delay, I2cdev};
use sgp41::Sgp41;

let dev = I2cdev::new("/dev/i2c-1").unwrap();
let mut sgp = Sgp41::new(dev, 0x59, Delay);

Doing Measurements

The SGP41 sensor provides both VOC and NOx measurements. The device performs measurements independently and calls to the driver fetch the latest information.

Basic VOC and NOx Measurements

use linux_embedded_hal as hal;
use hal::{Delay, I2cdev};

use std::time::Duration;
use std::thread;

use sgp41::Sgp41;

let dev = I2cdev::new("/dev/i2c-1").unwrap();
let mut sensor = Sgp41::new(dev, 0x59, Delay);

// Discard the first 45 samples as the algorithm is warming up.
for _ in 1..=45 {
    sensor.measure_voc_index().unwrap();
}

loop {
    // Individual measurements
    if let Ok(voc) = sensor.measure_voc_index() {
        println!("VOC index: {}", voc);
    }
     
    if let Ok(nox) = sensor.measure_nox_index() {
        println!("NOx index: {}", nox);
    }

    // Combined measurement (more efficient)
    if let Ok((voc, nox)) = sensor.measure_indices() {
        println!("Combined - VOC: {}, NOx: {}", voc, nox);
    }

    thread::sleep(Duration::new(1_u64, 0));
}

Temperature and Humidity Compensation

For improved accuracy, provide temperature and humidity data:

let humidity = 50_u16; // 50% RH
let temperature = 25_i16; // 25°C

// Compensated individual measurements
let voc = sensor.measure_voc_index_with_rht(humidity, temperature).unwrap();
let nox = sensor.measure_nox_index_with_rht(humidity, temperature).unwrap();

// Compensated combined measurement
let (voc, nox) = sensor.measure_indices_with_rht(humidity, temperature).unwrap();

Raw Signal Access

Access raw sensor signals for custom processing:

// Individual raw signals
let voc_raw = sensor.measure_raw().unwrap();
let nox_raw = sensor.measure_raw_nox().unwrap();

// Combined raw signals
let (voc_raw, nox_raw) = sensor.measure_raw_signals().unwrap();

Gas Index Calculation

Both VOC and NOx index calculations use the gas-index-algorithm crate which implements the official Sensirion algorithms and is no-std compatible.

• VOC index range: 1-500 (100 = average air quality)
• NOx index range: 1-500 (1 = average air quality)

Structs

Sgp41

Sgp41 driver instance

Enums

Error

Sgp41 errors