rp-hal-boards/rp2040-hal/examples/dht11.rs

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//! # DHT11 Example
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//!
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//! This application demonstrates how to read a DHT11 sensor on the RP2040.
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//!
//! It may need to be adapted to your particular board layout and/or pin assignment.
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//! In this example, the DHT11 data pin should be connected to GPIO28.
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//!
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//! NOTE: The DHT11 driver only works reliably when compiled in release mode.
//!
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//! See the `Cargo.toml` file for Copyright and license details.
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#![no_std]
#![no_main]
// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;
// Alias for our HAL crate
use rp2040_hal as hal;
// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use hal::pac;
// Some traits we need
use embedded_hal::digital::v2::InputPin;
use embedded_hal::digital::v2::OutputPin;
use hal::gpio::dynpin::DynPin;
use hal::Clock;
/// The linker will place this boot block at the start of our program image. We
/// need this to help the ROM bootloader get our code up and running.
/// Note: This boot block is not necessary when using a rp-hal based BSP
/// as the BSPs already perform this step.
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#[link_section = ".boot2"]
#[used]
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GENERIC_03H;
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/// External high-speed crystal on the Raspberry Pi Pico board is 12 MHz. Adjust
/// if your board has a different frequency
const XTAL_FREQ_HZ: u32 = 12_000_000u32;
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use dht_sensor::{dht11, DhtReading};
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/// A wrapper for DynPin, implementing both InputPin and OutputPin, to simulate
/// an open-drain pin as needed by the wire protocol the DHT11 sensor speaks.
/// https://how2electronics.com/interfacing-dht11-temperature-humidity-sensor-with-raspberry-pi-pico/
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struct InOutPin {
inner: DynPin,
}
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impl InOutPin {
fn new(inner: DynPin) -> Self {
Self { inner }
}
}
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impl InputPin for InOutPin {
type Error = rp2040_hal::gpio::Error;
fn is_high(&self) -> Result<bool, <Self as embedded_hal::digital::v2::InputPin>::Error> {
self.inner.is_high()
}
fn is_low(&self) -> Result<bool, <Self as embedded_hal::digital::v2::InputPin>::Error> {
self.inner.is_low()
}
}
impl OutputPin for InOutPin {
type Error = rp2040_hal::gpio::Error;
fn set_low(&mut self) -> Result<(), <Self as embedded_hal::digital::v2::OutputPin>::Error> {
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// To actively pull the pin low, it must also be configured as a (readable) output pin
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self.inner.into_readable_output();
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// In theory, we should set the pin to low first, to make sure we never actively
// pull it up. But if we try it on the input pin, we get Err(Gpio(InvalidPinType)).
self.inner.set_low()?;
Ok(())
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}
fn set_high(&mut self) -> Result<(), <Self as embedded_hal::digital::v2::OutputPin>::Error> {
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// To set the open-drain pin to high, just disable the output driver by changing the
// pin to input mode with pull-up. That way, the DHT11 can still pull the data line down
// to send its response.
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self.inner.into_pull_up_input();
Ok(())
}
}
/// Entry point to our bare-metal application.
///
/// The `#[rp2040_hal::entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables and the spinlock are initialised.
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///
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/// The function configures the RP2040 peripherals, assigns GPIO 28 to the
/// DHT11 driver, and takes a single measurement.
#[rp2040_hal::entry]
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fn main() -> ! {
// Grab our singleton objects
let mut pac = pac::Peripherals::take().unwrap();
let core = pac::CorePeripherals::take().unwrap();
// Set up the watchdog driver - needed by the clock setup code
let mut watchdog = hal::Watchdog::new(pac.WATCHDOG);
// Configure the clocks
let clocks = hal::clocks::init_clocks_and_plls(
XTAL_FREQ_HZ,
pac.XOSC,
pac.CLOCKS,
pac.PLL_SYS,
pac.PLL_USB,
&mut pac.RESETS,
&mut watchdog,
)
.ok()
.unwrap();
// The single-cycle I/O block controls our GPIO pins
let sio = hal::Sio::new(pac.SIO);
// Set the pins to their default state
let pins = hal::gpio::Pins::new(
pac.IO_BANK0,
pac.PADS_BANK0,
sio.gpio_bank0,
&mut pac.RESETS,
);
let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz());
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// Use GPIO 28 as an InOutPin
let mut pin = InOutPin::new(pins.gpio28.into());
pin.set_high().ok();
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// Perform a sensor reading
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let _measurement = dht11::Reading::read(&mut delay, &mut pin);
// In this case, we just ignore the result. A real application
// would do something with the measurement.
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loop {
cortex_m::asm::wfi();
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}
}
// End of file