Crate htu21df_sensor

About

This is a Rust driver for the HTU21D(F) temperature / humidity sensor by TE MEAS found in widely available sensor components. It was tested on GY-21 sensor but should work with different HTU21 based sensors too.

The implementation is based on the official datasheet by TE MEAS.

Example performing measurements with the HTU21D on the ESP32

In this example only the HTU21 (GY-21) is accessed over I²C but since in a real-world application that is unlikely to be the only slave device on the bus, the I²C struct is wrapped with the shared-bus crate.

 use esp_println::{print, println};
 use hal::{clock::ClockControl, gpio::IO, i2c::I2C, peripherals::Peripherals,
           prelude::*, Delay};
 use htu21df_sensor::Sensor;

 // set up clock and delay handle to ensure the proper duration between
 // measurement initiation and reading the result
 let clocks = ClockControl::max(system.clock_control).freeze();
 let mut delay = Delay::new(&clocks);

 // initialize I²C with the default GPIO pins on ESP32
 let i2c = I2C::new(
     peripherals.I2C0,
     io.pins.gpio21,
     io.pins.gpio22,
     100u32.kHz(),
     /* TODO: this will go away soon */
     &mut system.peripheral_clock_control,
     &clocks,
 );

 // wait for the sensor to become live; the 15 are suggested in the datasheet
 delay.delay_ms(15);

 // no need to own the I²C bus
 let bus = shared_bus::BusManagerSimple::new(i2c);

 // finally, initialize the sensor
 println!("initializing HTU21D ...");
 let mut htu = Sensor::new(bus.acquire_i2c(), Some(&mut delay)).expect("sensor init");

 // the sensor is now ready to use
 print!("measuring ...");
 let humidity: f32 = htu.measure_humidity(&mut delay).expect("humidity").value();
 let temperature: f32 = htu.measure_temperature(&mut delay).expect("temperature").value();

 println!(" done. temperature: {} °C, rel. humidity: {} %", temperature, humidity);

Implementation notes

As of version 0.1 only blocking APIs are provided.

Structs

• Measurement
  Two constants are required to perform a measurement: the command or register address C and the delay D in ms from initiating the measurement to reading the result. Both values are different for temperature and relative humidity on the HTU21.
• RawMeasurement
  Two bytes read from I²C bus representing a measurement. Values are provided in big endian order.
• Sensor
  Struct representing an interface to the HTU21D(F) on the I²C bus.

Enums

• Error
  Error conditions returned from struct Sensor member functions.

Type Aliases

• Humidity
  A type defining the measurement for relative humidity.
• Temperature
  A type defining the measurement for temperature.