Struct hc_sr04::HcSr04

pub struct HcSr04 { /* private fields */ }

HC-SR04 ultrasonic sensor on Raspberry Pi.

Fileds

• trig: TRIGGER output GPIO pin
• echo: ECHO input GPIO pin
• temp: ambient Temperature measure calibration
• sound_speed: speed of sound given the ambient Temperature
• timeout: ECHO pin polling timeout, considering the maximum measuring range of 4m for the sensor and the speed of sound given the ambient Temperature

Implementations

impl HcSr04

pub fn new(trig: u8, echo: u8, temp: Option<f32>) -> Result<Self>

Initialize HC-SR04 sensor and register GPIO interrupt on echo pin for RisingEdge events in order to poll it for bouncing UltraSonic waves detection.

Parameters

• trig: TRIGGER output GPIO pin
• echo: ECHO input GPIO pin
• temp: ambient TEMPERATURE used for calibration (if None defaults to 20.0)

Examples found in repository

examples/distance.rs (line 6)

fn run() -> Result<()> {
    // TRIGGER on GPIO Pin 24 & ECHO on GPIO Pin 23.
    let mut ultrasonic = HcSr04::new(24, 23, None)?;

    loop {
        match ultrasonic.measure_distance(Unit::Meters)? {
            Some(dist) => println!("Distance: {:.2}m", dist),
            None => println!("Object out of range"),
        }

        thread::sleep(Duration::from_secs(1));
    }
}

examples/door.rs (line 15)

fn run() -> Result<()> {
    // TRIGGER on GPIO Pin 24 & ECHO on GPIO Pin 23.
    let mut ultrasonic = HcSr04::new(24, 23, None)?;

    let below_threshold = |ultrasonic: &mut HcSr04| -> Result<bool> {
        Ok(ultrasonic
            .measure_distance(Unit::Meters)?
            .unwrap_or(f32::MAX)
            < THRESHOLD_DIST)
    };

    let mut closed = true;
    loop {
        // If measured distance is lower than THRESHOLD_DIST, door is open.
        if below_threshold(&mut ultrasonic)? == closed {
            closed = !closed;
            match closed {
                true => println!("Door closed!"),
                false => println!("Door opened!"),
            }
        }

        thread::sleep(Duration::from_millis(500));
    }
}

pub fn calibrate(&mut self, temp: f32)

Calibrate the sensor with the given ambient temperature (temp) expressed as Celsius degrees.

pub fn measure_distance(&mut self, unit: Unit) -> Result<Option<f32>>

Perform distance measurement.

Returns Ok variant if measurement succedes. Inner Option value is None if no object is present within maximum measuring range (4m); otherwhise, on Some variant instead, contained value represents distance expressed as the specified unit (unit of measure).

Examples found in repository

examples/distance.rs (line 9)

fn run() -> Result<()> {
    // TRIGGER on GPIO Pin 24 & ECHO on GPIO Pin 23.
    let mut ultrasonic = HcSr04::new(24, 23, None)?;

    loop {
        match ultrasonic.measure_distance(Unit::Meters)? {
            Some(dist) => println!("Distance: {:.2}m", dist),
            None => println!("Object out of range"),
        }

        thread::sleep(Duration::from_secs(1));
    }
}

examples/door.rs (line 19)

fn run() -> Result<()> {
    // TRIGGER on GPIO Pin 24 & ECHO on GPIO Pin 23.
    let mut ultrasonic = HcSr04::new(24, 23, None)?;

    let below_threshold = |ultrasonic: &mut HcSr04| -> Result<bool> {
        Ok(ultrasonic
            .measure_distance(Unit::Meters)?
            .unwrap_or(f32::MAX)
            < THRESHOLD_DIST)
    };

    let mut closed = true;
    loop {
        // If measured distance is lower than THRESHOLD_DIST, door is open.
        if below_threshold(&mut ultrasonic)? == closed {
            closed = !closed;
            match closed {
                true => println!("Door closed!"),
                false => println!("Door opened!"),
            }
        }

        thread::sleep(Duration::from_millis(500));
    }
}

Trait Implementations

impl Debug for HcSr04

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.