sgp4x

Platform agnostic Rust device driver for Sensirion SGP4x created based on https://crates.io/crates/sgp40. At the moment, it supports both SGP41 and SGP40 (although NOx will fail for SGP40)

Platform agnostic Rust driver for Sensirion SGP41 gas sensor using the embedded-hal traits.

Sensirion SGP4X

Sensirion SGP4X is a low-power accurate gas sensor for air quality applications. The sensor uses I²C interface and measures both VOC (Total Volatile Organic Compounds) and NOx (Nitrogen Oxides) providing comprehensive air quality monitoring capabilities.

Key features:

• Dual gas measurement: VOC and NOx indices
• Temperature/humidity compensation: Improved accuracy with environmental data
• Low power consumption: Optimized for battery-powered applications
• I²C interface: Simple integration with 0x59 address
• No-std compatible: Works in embedded environments
• Gas index algorithms: Uses official Sensirion algorithms via gas-index-algorithm crate

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

Usage

Basic VOC and NOx Measurements

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

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

// Warm up the sensor (first 45 samples should be discarded)
for _ in 0..45 {
    sensor.measure_voc_index().ok();
}

// Individual measurements
let voc_index = sensor.measure_voc_index()?; // 1-500 (100 = average)
let nox_index = sensor.measure_nox_index()?; // 1-500 (1 = average)

// Combined measurement (more efficient)
let (voc, nox) = sensor.measure_indices()?;

Temperature and Humidity Compensation

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

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

// Combined compensated measurement
let (voc, nox) = sensor.measure_indices_with_rht(humidity, temperature)?;

Raw Signal Access

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

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

SGP41-Specific Features

// Conditioning (recommended for new sensors)
sensor.execute_conditioning()?;

// Conditioning with VOC reading
sensor.execute_conditioning_with_voc_read()?;

Migration from SGP40

The SGP41 driver maintains API compatibility with SGP40 for VOC measurements:

// SGP40 code
use sgp40::Sgp40;
let mut sensor = Sgp40::new(i2c, 0x59, delay);
let voc = sensor.measure_voc_index()?;

// SGP41 equivalent  
use sgp41::Sgp41;
let mut sensor = Sgp41::new(i2c, 0x59, delay);
let voc = sensor.measure_voc_index()?; // Same API
let nox = sensor.measure_nox_index()?; // New capability

Examples

• main.rs - Linux example showing all measurement types
• nrf52-example - Embedded no-std example for NRF52

Development status

The crate is feature complete with full VOC and NOx measurement capabilities.

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.

Contributing

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.