2022-01-29 07:57:51 +11:00
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//! # DHT11 Example
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2022-01-24 07:02:43 +11:00
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//!
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2022-01-29 07:57:51 +11:00
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//! This application demonstrates how to read a DHT11 sensor on the RP2040.
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2022-01-24 07:02:43 +11:00
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//!
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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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2022-01-29 09:17:44 +11:00
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//! NOTE: The DHT11 driver only works reliably when compiled in release mode.
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//!
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2022-04-18 20:49:41 +10:00
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//! See the `Cargo.toml` file for Copyright and license details.
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2022-01-24 07:02:43 +11:00
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#![no_std]
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#![no_main]
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// Ensure we halt the program on panic (if we don't mention this crate it won't
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// be linked)
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use panic_halt as _;
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// Alias for our HAL crate
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use rp2040_hal as hal;
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// A shorter alias for the Peripheral Access Crate, which provides low-level
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// register access
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use hal::pac;
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// Some traits we need
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use embedded_hal::digital::v2::InputPin;
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use embedded_hal::digital::v2::OutputPin;
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use hal::gpio::dynpin::DynPin;
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use hal::Clock;
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/// The linker will place this boot block at the start of our program image. We
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/// need this to help the ROM bootloader get our code up and running.
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2022-09-02 15:38:58 +10:00
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/// Note: This boot block is not necessary when using a rp-hal based BSP
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/// as the BSPs already perform this step.
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#[link_section = ".boot2"]
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#[used]
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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
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/// if your board has a different frequency
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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
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/// an open-drain pin as needed by the wire protocol the DHT11 sensor speaks.
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/// https://how2electronics.com/interfacing-dht11-temperature-humidity-sensor-with-raspberry-pi-pico/
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struct InOutPin {
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inner: DynPin,
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}
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impl InOutPin {
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fn new(inner: DynPin) -> Self {
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Self { inner }
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}
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}
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impl InputPin for InOutPin {
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type Error = rp2040_hal::gpio::Error;
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fn is_high(&self) -> Result<bool, <Self as embedded_hal::digital::v2::InputPin>::Error> {
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self.inner.is_high()
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}
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fn is_low(&self) -> Result<bool, <Self as embedded_hal::digital::v2::InputPin>::Error> {
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self.inner.is_low()
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}
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}
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impl OutputPin for InOutPin {
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type Error = rp2040_hal::gpio::Error;
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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
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// pull it up. But if we try it on the input pin, we get Err(Gpio(InvalidPinType)).
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self.inner.set_low()?;
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Ok(())
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}
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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
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// pin to input mode with pull-up. That way, the DHT11 can still pull the data line down
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// to send its response.
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self.inner.into_pull_up_input();
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Ok(())
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}
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}
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/// Entry point to our bare-metal application.
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///
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2022-08-22 04:01:45 +10:00
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/// The `#[rp2040_hal::entry]` macro ensures the Cortex-M start-up code calls this function
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/// 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
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/// DHT11 driver, and takes a single measurement.
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#[rp2040_hal::entry]
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fn main() -> ! {
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// Grab our singleton objects
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let mut pac = pac::Peripherals::take().unwrap();
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let core = pac::CorePeripherals::take().unwrap();
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// Set up the watchdog driver - needed by the clock setup code
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let mut watchdog = hal::Watchdog::new(pac.WATCHDOG);
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// Configure the clocks
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let clocks = hal::clocks::init_clocks_and_plls(
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XTAL_FREQ_HZ,
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pac.XOSC,
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pac.CLOCKS,
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pac.PLL_SYS,
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pac.PLL_USB,
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&mut pac.RESETS,
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&mut watchdog,
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)
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.ok()
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.unwrap();
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// The single-cycle I/O block controls our GPIO pins
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let sio = hal::Sio::new(pac.SIO);
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// Set the pins to their default state
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let pins = hal::gpio::Pins::new(
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pac.IO_BANK0,
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pac.PADS_BANK0,
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sio.gpio_bank0,
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&mut pac.RESETS,
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);
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2022-08-19 05:14:51 +10:00
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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
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let mut pin = InOutPin::new(pins.gpio28.into());
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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);
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// In this case, we just ignore the result. A real application
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// would do something with the measurement.
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loop {
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cortex_m::asm::wfi();
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}
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}
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// End of file
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