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0.1.0 | Jul 15, 2024 |
#176 in Hardware support
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49KB
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sds011-rs
This crate implements a driver for the SDS011 particle sensor based on
embedded-hal
.
Thanks to this abstraction layer, it can be used on full-fledged operating
systems as well as embedded devices.
Features
sync
: To use the synchronous interface, enable this feature. By default, this library exposes an async API.
Examples
The crate ships with two small CLI examples that utilize the library:
cli.rs
uses the synchronous interface (embedded-io),cli_async.rs
uses the asynchronous interface (embedded-io-async).
The example below demonstrates how to use the sensor with an ESP32, showcasing the strength of the embedded-hal abstractions.
#![no_std]
#![no_main]
use embassy_executor::Spawner;
use embassy_time::{Duration, Timer, Delay};
use esp_backtrace as _;
use esp_hal::{
clock::ClockControl,
gpio::Io,
peripherals::Peripherals,
prelude::*,
system::SystemControl,
timer::timg::TimerGroup,
uart::{config::Config, TxRxPins, Uart},
};
use esp_println::println;
use sds011::SDS011;
#[main]
async fn main(_s: Spawner) -> ! {
let peripherals = Peripherals::take();
let system = SystemControl::new(peripherals.SYSTEM);
let clocks = ClockControl::max(system.clock_control).freeze();
let timg0 = TimerGroup::new(peripherals.TIMG0, &clocks);
esp_hal_embassy::init(&clocks, timg0.timer0);
let io = Io::new(peripherals.GPIO, peripherals.IO_MUX);
let (tx_pin, rx_pin) = (io.pins.gpio3, io.pins.gpio2);
let config = Config::default()
.baudrate(9600)
.rx_fifo_full_threshold(sds011::READ_BUF_SIZE as u16);
let mut uart1 =
Uart::new_async_with_config(peripherals.UART1, config, &clocks, tx_pin, rx_pin).unwrap();
let sds011 = SDS011::new(&mut uart1, sds011::Config::default());
let mut sds011 = sds011.init(&mut Delay).await.unwrap();
println!("SDS011 version {}, ID {}", sds011.version(), sds011.id());
loop {
let dust = sds011.measure(&mut Delay).await.unwrap();
println!("{}", dust);
Timer::after(Duration::from_millis(30_000)).await;
}
}
Technical Overview
The sensor has two operating modes:
- "query mode": The sensor does nothing until it is actively instructed to perform a measurement (we call this polling).
- "active mode": The sensor continuously produces data in a configurable interval (we call this periodic).
We abstract this into the following interface:
- A sensor created using
new()
is inUninitialized
state. No serial communication is performed during creation. - You call
init()
. This will return a sensor inPolling
state. The sensor is instructed via serial commands to switch to query mode and goes to sleep (fan off). - The sensor can now be queried via the
measure()
function. This will wake the sensor, spin the fan for a configurable duration (which is necessary to get a correct measurement), read the sensor and put it back to sleep. - Optionally (not recommended!), the sensor can be put into
Periodic
state by callingmake_periodic()
on a sensor inPolling
state. This puts the sensor in charge of sleeping and waking up. Since it will continuously produce data, make sure to callmeasure()
in time so the serial output buffer does not overflow.
Limitations
This abstraction does not yet support sending commands only to a specific sensor id (it effectively uses broadcast mode all the time). This feature seemed irrelevant, but the backend code for it is completely implemented, so this may change in a future version if there is demand. Also, putting sensors into periodic mode can have the side effect of missing package boundaries. The current version cannot recover from this; it will return an error. Close the serial port and retry, or probably better, just don't use periodic mode.
Acknowledgements
Thank you to Tim Orme, who implemented sds011lib in Python and wrote documentation that pointed me in the right direction, especially to:
for the SDS011 sensor.
License: MIT OR Apache-2.0
Dependencies
~0.4–0.8MB
~18K SLoC