CO2 Sensor SCD30 for Rust

This is yet another implementation of a Sensirion SCD30 i2c sensor driver in pure rust. The sensor measures CO2, temperature and humidity.

The sensor documentation can be obtained directly from Sensirion: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9.5_CO2/Sensirion_CO2_Sensors_SCD30_Interface_Description.pdf

The target platform is a Raspberry pi so either you compile it on an rpi or use crosscompiling. It is based on Raspberry Pi Peripheral Access Library (https://crates.io/crates/rppal). The physical SCD30 connection to i2c can be done by wiring the device to the first i2c ports of the GPIO connector.

Connect to RaspberryPi GPIO:

• pin 1 (3.3V/VCC)
• pin 3 (SDA)
• pin 5 (SCL)
• pin 6 (GND).

Example

use scd30pi::i2c::SCD30;
use std::{thread, time};

fn main() {
    let mut sensor = SCD30::new().unwrap();
    let speed = sensor.get_bus_speed().unwrap();
    println!("bus Speed: {}", speed);

    sensor.start().unwrap();
    sensor.set_measure_interval(2).unwrap();

    let version = sensor.read_firmware_version().unwrap();
    println!("Current firmware version {}", version);

    while !sensor.data_available().unwrap() {
        thread::sleep(time::Duration::from_millis(200));
    }

    let temperature = sensor.temperature().unwrap();
    let co2 = sensor.co2().unwrap();
    let humidity = sensor.humidity().unwrap();

    println!(
        "co2 = {:.0} ppm, temp = {:.2} °C, humidity = {:.0} %",
        co2, temperature, humidity
    );
}

Cross Compile

• Install the arm cross compiler. You can find the crosscompiler on https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-a/downloads you can unpack the content to the directory of your choice. Assume it is TARGET_DIR then export following variables prior to use cargo to cross compile:

  export CC_armv7_unknown_linux_gnueabihf=arm-none-linux-gnueabihf-gcc export PATH=${TARGET_DIR}/gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf/bin:$PATH

• Install rust cross compile target.

  rustup target add armv7-unknown-linux-gnueabihf

• Configure cargo for the cross compiler target. Add following to ~/.cargo/config

  [target.armv7-unknown-linux-gnueabihf]

  linker = "arm-linux-gnueabihf-gcc"

Copile using:

cargo build --target=armv7-unknown-linux-gnueabihf --release

Additional resources about cross compiling can be found at https://github.com/japaric/rust-cross