Gihex HC-SR04

Introduction

This is the library used to access the HC-SR04 ultrasonic sensor. This library inspired by hc-sr04.
For more detail how to use this library see Example.

Features

• Measure distance.
• Get last duration ultrasonic wave returned
• Set environment temperature for compensation. Only available if feature temperature or humidity enabled.
• Set environment humidity for compensation. Only available if feature humidity enabled.

How to Use?

To use this library, there are several things that must be done, such as:

• Implementing external interrupt (EXTI) with RAISING and FAILING trigger to the pin echo (pin microcontroller that connected to the pin echo HC-SR04 sensor).

let mut echo_pin = gpioa.pa3.into_pull_down_input(&mut gpioa.crl);
echo_pin.make_interrupt_source(&mut afio);
let mut exti = ctx.device.EXTI;
echo_pin.enable_interrupt(&mut exti);
echo_pin.trigger_on_edge(&mut exti, Edge::RisingFalling);

• Create an object that impelements trait us_timer::TickerUs. This object is used to count the number of ticks.

use stm32f1xx_hal::timer::{CounterUs, Instance};
pub struct MyCounter<TIM> {
    counter: CounterUs<TIM>,
}

impl<TIM: Instance> MyCounter<TIM> {
    fn new(counter: CounterUs<TIM>) -> Self {
        Self { counter }
    }
}

impl<TIM: Instance> TickerUs for MyCounter<TIM> {
    fn get_tick(&self) -> u32 {
        self.counter.now().ticks()
    }

    fn get_frequency(&self) -> u32 {
        1_000_000
    }
}

• Create HC-SR04 object and use it.

let hcsr04 = HcSR04::hc_sr04_new(trig_pin, &mut delay, &mut my_counter);
let distance=hcsr04.get_distance::<f32>(DistanceUnit::MilliMeter);