Crate tmp108 

This is a platform-agnostic Rust driver for the TMP108 temperature sensor based on the embedded-hal traits.

For further details of the device architecture and operation, please refer to the official Datasheet.

Operational notes

I²C bus ownership

The driver assumes single-master ownership of the TMP108. Several methods (notably configure, one_shot, and shutdown on both Tmp108 and [AsyncTmp108]) perform a read-modify-write on the configuration register as two distinct I²C transactions. On a multi-master bus, a second master writing to register 0x01 between the read and the write will silently lose those writes — the TMP108 has no register-level lock. In multi-master designs, serialise driver access at a higher level (e.g. a bus mutex around the entire driver, not just individual I²C transactions).

Driver lifecycle on drop

Dropping a Tmp108, [AsyncTmp108] or [AlertTmp108] does not change the chip’s operating mode. The chip retains whatever M bits were last written. If you want the chip to stop drawing current after the driver goes out of scope, call Tmp108::shutdown or [AsyncTmp108::shutdown] (or finish an [AsyncTmp108::continuous] call cleanly) before dropping.

In particular, dropping the future returned by [AsyncTmp108::continuous] mid-flight (e.g. via embassy_futures::select! or tokio::time::timeout) leaves the chip in Mode::Continuous indefinitely. See the cancel-safety note on that method.

TMP108

A #[no_std] platform-agnostic driver for the TMP108 temperature sensor using the embedded-hal traits.

I²C addresses

The TMP108 can take one of 4 I²C addresses depending on the state of the A0 pin:

A0	Addr
GND	0x48
V+	0x49
SDA	0x4a
SCL	0x4b

The driver has dedicated constructors for each — new_with_a0_gnd, new_with_a0_vplus, new_with_a0_sda, new_with_a0_scl — so an invalid address cannot be requested.

Usage

Blocking one-shot read

let hal = Hal::new();
let i2c = hal.i2c();

let mut tmp = Tmp108::new_with_a0_gnd(i2c);
let temperature = tmp.temperature().map_err(|_| anyhow!("Failed to read temperature"))?;
println!("Temperature: {temperature:.2} C");

Async continuous conversions

let hal = Hal::new();
let i2c = hal.i2c();
let mut delay = hal.delay();

let mut tmp = AsyncTmp108::new_with_a0_gnd(i2c);

tmp.continuous(async |t| {
    for _ in 0..5 {
        let temperature = t.wait_for_temperature(&mut delay).await?;
        println!("Temperature: {temperature:.2} C");
    }
    Ok(())
})
.await
.map_err(|_| anyhow!("Continuous conversion failed"))?;

Async interrupt-mode threshold alert

let mut tmp = AlertTmp108::new_with_a0_gnd(i2c, alert);

tmp.sensor_mut()
    .configure(Config {
        thermostat_mode: Thermostat::Interrupt,
        alert_polarity: Polarity::ActiveLow,
        ..Default::default()
    })
    .await
    .map_err(|_| anyhow!("Failed to configure TMP108"))?;

tmp.set_temperature_threshold_low(15.0)
    .await
    .map_err(|_| anyhow!("Failed to set low threshold"))?;
tmp.set_temperature_threshold_high(30.0)
    .await
    .map_err(|_| anyhow!("Failed to set high threshold"))?;

println!("Waiting for ALERT (warm the sensor above 30 C)...");
let temperature = tmp
    .wait_for_temperature_threshold()
    .await
    .map_err(|_| anyhow!("wait_for_temperature_threshold failed"))?;
println!("ALERT! Temperature at trigger: {temperature:.2} C");

See examples/ for complete, runnable versions of each snippet (and more).

Cargo features

Feature	Effect	Implies
(none)	Blocking Tmp108 over embedded-hal.	—
async	Async AsyncTmp108 over embedded-hal-async. AsyncTmp108::continuous is unlocked.	—
embedded-sensors-hal	Blocking TemperatureSensor impl on Tmp108.	—
embedded-sensors-hal-async	Async TemperatureSensor, TemperatureThresholdSet, TemperatureHysteresis impls on AsyncTmp108, plus the AlertTmp108 wrapper with TemperatureThresholdWait.	async

Since 0.6.0 both Tmp108 (blocking) and AsyncTmp108 (async) are available simultaneously when both relevant features are enabled.

Gotchas

• Constructors are infallible. They take no delay; the delay only appears on wait_for_temperature, where it is genuinely needed to wait out a conversion period.
• Comparator vs interrupt mode latching. In comparator mode the ALERT pin stays asserted until temperature returns inside (T_low + HYS, T_high − HYS). In interrupt mode the pin clears as soon as the configuration register is read (the driver does this for you inside wait_for_temperature_threshold). See examples/alert_comparator.rs for a demonstration.
• ALERT polarity is set on-chip. Wire your pull resistor for the polarity you configured. Examples assume active-low + external pull-up.
• AsyncTmp108::continuous is async-only. For blocking continuous-mode use, call Tmp108::configure(...) to set Mode::Continuous manually, loop on Tmp108::wait_for_temperature(&mut delay), then call Tmp108::shutdown().
• AsyncTmp108::continuous future is not cancel-safe. Dropping it before completion (e.g. via embassy_futures::select! or tokio::time::timeout) leaves the chip in Mode::Continuous. See the method’s doc.
• Temperature scale. Raw register values are 12-bit signed in the upper bits of a 16-bit register at 0.0625 °C/LSB. The driver models this as Celsius, a newtype over sixteenths of a degree whose 4096 inhabitants are exactly the temperatures the part can report or accept as a limit. Celsius::try_from_degrees is the single fallible parse (it rejects NaN, infinities and out-of-range values, and rounds half away from zero); Celsius::to_degrees renders back to f32, and Display honours precision so {t:.2} works. The embedded-sensors-hal trait impls keep their DegreesCelsius (f32) signatures and translate at the boundary.

MSRV

Rust 1.94 and up.

License

Licensed under the terms of the MIT license.

Contribution

Unless you explicitly state otherwise, any contribution submitted for inclusion in the work by you shall be licensed under the terms of the MIT license.

See CONTRIBUTING.md for the full contribution workflow, including the Conventional Commits v1.0.0 commit-message format this repository uses.

Structs

Celsius

A temperature the TMP108 can represent.

Config

Tmp108 configuration parameters

Tmp108

Tmp108 device driver. Blocking TMP108 driver.

Enums

A0

A0 pin logic level representation.

ConversionRate

Conversion rate

Error

Tmp108 Errors

Hysteresis

Temperature hysteresis

Mode

Device functional mode

OutOfRange

Why a value could not be converted into a Celsius.

Polarity

ALERT pin polarity

Thermostat

Thermostat mode