Add 0x09_dht11_rust: DHT11 temperature/humidity sensor driver

2026-07-19 02:17:34 +02:00 · 2026-03-25 21:21:35 -04:00
parent 3ade64aff8
commit 7720434862
18 changed files with 2022 additions and 0 deletions
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+//! @file board.rs
+//! @brief Board-level HAL helpers for the DHT11 driver
+//! @author Kevin Thomas
+//! @date 2025
+//!
+//! MIT License
+//!
+//! Copyright (c) 2025 Kevin Thomas
+//!
+//! Permission is hereby granted, free of charge, to any person obtaining a copy
+//! of this software and associated documentation files (the "Software"), to deal
+//! in the Software without restriction, including without limitation the rights
+//! to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//! copies of the Software, and to permit persons to whom the Software is
+//! furnished to do so, subject to the following conditions:
+//!
+//! The above copyright notice and this permission notice shall be included in
+//! all copies or substantial portions of the Software.
+//!
+//! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//! IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//! FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//! AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//! LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//! OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//! SOFTWARE.
+
+// DHT11 pure-logic functions (checksum, parsing, formatting)
+use crate::dht11;
+// Rate extension trait for .Hz() baud rate construction
+use fugit::RateExtU32;
+// Clock trait for accessing system clock frequency
+use hal::Clock;
+// GPIO pin types and function selectors
+use hal::gpio::{FunctionNull, FunctionUart, Pin, PullDown, PullNone};
+// UART configuration and peripheral types
+use hal::uart::{DataBits, Enabled, StopBits, UartConfig, UartPeripheral};
+
+// Alias our HAL crate
+#[cfg(rp2350)]
+use rp235x_hal as hal;
+#[cfg(rp2040)]
+use rp2040_hal as hal;
+
+// Timer device type for the HAL timer peripheral
+#[cfg(rp2350)]
+pub(crate) type HalTimer = hal::Timer<hal::timer::CopyableTimer0>;
+// Timer type alias for RP2040 (non-generic)
+#[cfg(rp2040)]
+pub(crate) type HalTimer = hal::Timer;
+
+/// External crystal frequency in Hz (12 MHz).
+pub(crate) const XTAL_FREQ_HZ: u32 = 12_000_000u32;
+
+/// UART baud rate in bits per second.
+pub(crate) const UART_BAUD: u32 = 115_200;
+
+/// GPIO pin number connected to the DHT11 data line.
+pub(crate) const DHT11_GPIO: u8 = 4;
+
+/// Polling interval in milliseconds (DHT11 minimum is 2 seconds).
+pub(crate) const POLL_MS: u32 = 2_000;
+
+/// Type alias for the configured TX pin (GPIO 0, UART function, no pull).
+pub(crate) type TxPin = Pin<hal::gpio::bank0::Gpio0, FunctionUart, PullNone>;
+
+/// Type alias for the configured RX pin (GPIO 1, UART function, no pull).
+pub(crate) type RxPin = Pin<hal::gpio::bank0::Gpio1, FunctionUart, PullNone>;
+
+/// Type alias for the default TX pin state from `Pins::new()`.
+pub(crate) type TxPinDefault = Pin<hal::gpio::bank0::Gpio0, FunctionNull, PullDown>;
+
+/// Type alias for the default RX pin state from `Pins::new()`.
+pub(crate) type RxPinDefault = Pin<hal::gpio::bank0::Gpio1, FunctionNull, PullDown>;
+
+/// Type alias for the fully-enabled UART0 peripheral with TX/RX pins.
+pub(crate) type EnabledUart = UartPeripheral<Enabled, hal::pac::UART0, (TxPin, RxPin)>;
+
+/// Initialise system clocks and PLLs from the external 12 MHz crystal.
+///
+/// # Arguments
+///
+/// * `xosc` - XOSC peripheral singleton.
+/// * `clocks` - CLOCKS peripheral singleton.
+/// * `pll_sys` - PLL_SYS peripheral singleton.
+/// * `pll_usb` - PLL_USB peripheral singleton.
+/// * `resets` - Mutable reference to the RESETS peripheral.
+/// * `watchdog` - Mutable reference to the watchdog timer.
+///
+/// # Returns
+///
+/// Configured clocks manager.
+///
+/// # Panics
+///
+/// Panics if clock initialisation fails.
+pub(crate) fn init_clocks(
+    xosc: hal::pac::XOSC,
+    clocks: hal::pac::CLOCKS,
+    pll_sys: hal::pac::PLL_SYS,
+    pll_usb: hal::pac::PLL_USB,
+    resets: &mut hal::pac::RESETS,
+    watchdog: &mut hal::Watchdog,
+) -> hal::clocks::ClocksManager {
+    hal::clocks::init_clocks_and_plls(
+        XTAL_FREQ_HZ, xosc, clocks, pll_sys, pll_usb, resets, watchdog,
+    )
+    .unwrap()
+}
+
+/// Unlock the GPIO bank and return the pin set.
+///
+/// # Arguments
+///
+/// * `io_bank0` - IO_BANK0 peripheral singleton.
+/// * `pads_bank0` - PADS_BANK0 peripheral singleton.
+/// * `sio` - SIO peripheral singleton.
+/// * `resets` - Mutable reference to the RESETS peripheral.
+///
+/// # Returns
+///
+/// GPIO pin set for the entire bank.
+pub(crate) fn init_pins(
+    io_bank0: hal::pac::IO_BANK0,
+    pads_bank0: hal::pac::PADS_BANK0,
+    sio: hal::pac::SIO,
+    resets: &mut hal::pac::RESETS,
+) -> hal::gpio::Pins {
+    let sio = hal::Sio::new(sio);
+    hal::gpio::Pins::new(io_bank0, pads_bank0, sio.gpio_bank0, resets)
+}
+
+/// Initialise UART0 for serial output (stdio equivalent).
+///
+/// # Arguments
+///
+/// * `uart0` - PAC UART0 peripheral singleton.
+/// * `tx_pin` - GPIO pin to use as UART0 TX (GPIO 0).
+/// * `rx_pin` - GPIO pin to use as UART0 RX (GPIO 1).
+/// * `resets` - Mutable reference to the RESETS peripheral.
+/// * `clocks` - Reference to the initialised clock configuration.
+///
+/// # Returns
+///
+/// Enabled UART0 peripheral ready for blocking writes.
+///
+/// # Panics
+///
+/// Panics if the HAL cannot achieve the requested baud rate.
+pub(crate) fn init_uart(
+    uart0: hal::pac::UART0,
+    tx_pin: TxPinDefault,
+    rx_pin: RxPinDefault,
+    resets: &mut hal::pac::RESETS,
+    clocks: &hal::clocks::ClocksManager,
+) -> EnabledUart {
+    let pins = (
+        tx_pin.reconfigure::<FunctionUart, PullNone>(),
+        rx_pin.reconfigure::<FunctionUart, PullNone>(),
+    );
+    let cfg = UartConfig::new(UART_BAUD.Hz(), DataBits::Eight, None, StopBits::One);
+    UartPeripheral::new(uart0, pins, resets)
+        .enable(cfg, clocks.peripheral_clock.freq())
+        .unwrap()
+}
+
+/// Create a blocking delay timer from the ARM SysTick peripheral.
+///
+/// # Arguments
+///
+/// * `clocks` - Reference to the initialised clock configuration.
+///
+/// # Returns
+///
+/// Blocking delay provider.
+///
+/// # Panics
+///
+/// Panics if the cortex-m core peripherals have already been taken.
+pub(crate) fn init_delay(clocks: &hal::clocks::ClocksManager) -> cortex_m::delay::Delay {
+    let core = cortex_m::Peripherals::take().unwrap();
+    cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz())
+}
+
+/// Drive the DHT11 data pin to a given level (enables output).
+///
+/// # Arguments
+///
+/// * `high` - `true` to drive HIGH, `false` to drive LOW.
+fn gpio_drive(high: bool) {
+    unsafe {
+        let sio = &*hal::pac::SIO::PTR;
+        if high {
+            sio.gpio_out_set().write(|w| w.bits(1u32 << DHT11_GPIO));
+        } else {
+            sio.gpio_out_clr().write(|w| w.bits(1u32 << DHT11_GPIO));
+        }
+        sio.gpio_oe_set().write(|w| w.bits(1u32 << DHT11_GPIO));
+    }
+}
+
+/// Release the DHT11 data pin back to input mode (disable output driver).
+fn gpio_release() {
+    unsafe {
+        let sio = &*hal::pac::SIO::PTR;
+        sio.gpio_oe_clr().write(|w| w.bits(1u32 << DHT11_GPIO));
+    }
+}
+
+/// Read the current logic level of the DHT11 data pin.
+///
+/// # Returns
+///
+/// `true` if the pin reads HIGH, `false` if LOW.
+fn gpio_read() -> bool {
+    unsafe { (*hal::pac::SIO::PTR).gpio_in().read().bits() & (1u32 << DHT11_GPIO) != 0 }
+}
+
+/// Read the free-running microsecond timer (lower 32 bits).
+///
+/// # Arguments
+///
+/// * `timer` - Reference to the HAL timer peripheral.
+///
+/// # Returns
+///
+/// Current timer value in microseconds (wrapping at 2^32).
+fn time_us_32(timer: &HalTimer) -> u32 {
+    timer.get_counter().ticks() as u32
+}
+
+/// Send the DHT11 start signal on the data pin.
+///
+/// Drives the pin LOW for 18 ms then HIGH for 40 us before switching
+/// the pin to input mode to listen for the sensor response.
+///
+/// # Arguments
+///
+/// * `delay` - Mutable reference to the blocking delay provider.
+fn send_start_signal(delay: &mut cortex_m::delay::Delay) {
+    gpio_drive(false);
+    delay.delay_ms(18);
+    gpio_drive(true);
+    delay.delay_us(40);
+    gpio_release();
+}
+
+/// Spin until the pin leaves the given logic level, or time out.
+///
+/// # Arguments
+///
+/// * `level` - Logic level to wait through (`true` = HIGH, `false` = LOW).
+///
+/// # Returns
+///
+/// `true` once the level changed, `false` on timeout.
+fn wait_for_level(level: bool) -> bool {
+    let mut timeout: u32 = dht11::LEVEL_WAIT_TIMEOUT;
+    while gpio_read() == level {
+        timeout -= 1;
+        if timeout == 0 {
+            return false;
+        }
+    }
+    true
+}
+
+/// Wait for the DHT11 response after the start signal.
+///
+/// The sensor pulls LOW then HIGH then LOW again; each transition
+/// is awaited with a timeout.
+///
+/// # Returns
+///
+/// `true` if the full response was received, `false` on timeout.
+fn wait_response() -> bool {
+    wait_for_level(true) && wait_for_level(false) && wait_for_level(true)
+}
+
+/// Read a single bit from the DHT11 data stream.
+///
+/// Waits for the low-period to end, measures the high-period duration,
+/// and accumulates the result into the data array via
+/// [`dht11::accumulate_bit`].
+///
+/// # Arguments
+///
+/// * `data` - 5-byte array accumulating the received bits.
+/// * `i` - Bit index (0–39).
+/// * `timer` - Reference to the HAL timer for microsecond measurement.
+///
+/// # Returns
+///
+/// `true` on success, `false` on timeout.
+fn read_bit(data: &mut [u8; 5], i: usize, timer: &HalTimer) -> bool {
+    if !wait_for_level(false) {
+        return false;
+    }
+    let start = time_us_32(timer);
+    if !wait_for_level(true) {
+        return false;
+    }
+    let duration = time_us_32(timer).wrapping_sub(start);
+    dht11::accumulate_bit(data, i, duration);
+    true
+}
+
+/// Read all 40 data bits from the DHT11.
+///
+/// # Arguments
+///
+/// * `data` - 5-byte array filled with the received data.
+/// * `timer` - Reference to the HAL timer for microsecond measurement.
+///
+/// # Returns
+///
+/// `true` if all 40 bits were read, `false` on timeout.
+fn read_40_bits(data: &mut [u8; 5], timer: &HalTimer) -> bool {
+    for i in 0..40 {
+        if !read_bit(data, i, timer) {
+            return false;
+        }
+    }
+    true
+}
+
+/// Execute the full DHT11 read protocol.
+///
+/// Sends the start signal, waits for the sensor response, reads 40 bits
+/// of data, validates the checksum, and parses humidity and temperature.
+///
+/// # Arguments
+///
+/// * `timer` - Reference to the HAL timer for microsecond measurement.
+/// * `delay` - Mutable reference to the blocking delay provider.
+///
+/// # Returns
+///
+/// `Some((humidity, temperature))` on success, `None` on failure.
+pub(crate) fn read_sensor(
+    timer: &HalTimer,
+    delay: &mut cortex_m::delay::Delay,
+) -> Option<(f32, f32)> {
+    let mut data = [0u8; 5];
+    send_start_signal(delay);
+    if !wait_response() {
+        return None;
+    }
+    if !read_40_bits(&mut data, timer) {
+        return None;
+    }
+    if !dht11::validate_checksum(&data) {
+        return None;
+    }
+    Some((dht11::parse_humidity(&data), dht11::parse_temperature(&data)))
+}
+
+/// Read the sensor, format the result, write it over UART, and wait.
+///
+/// On a successful read, prints humidity and temperature; on failure,
+/// prints a wiring-check message. Always waits [`POLL_MS`] before
+/// returning to respect the DHT11 minimum polling interval.
+///
+/// # Arguments
+///
+/// * `uart` - Reference to the enabled UART peripheral for serial output.
+/// * `timer` - Reference to the HAL timer for microsecond measurement.
+/// * `delay` - Mutable reference to the blocking delay provider.
+pub(crate) fn poll_sensor(
+    uart: &EnabledUart,
+    timer: &HalTimer,
+    delay: &mut cortex_m::delay::Delay,
+) {
+    let mut buf = [0u8; 64];
+    let n = match read_sensor(timer, delay) {
+        Some((h, t)) => dht11::format_reading(&mut buf, h, t),
+        None => dht11::format_error(&mut buf, DHT11_GPIO),
+    };
+    buf[n] = b'\r';
+    buf[n + 1] = b'\n';
+    uart.write_full_blocking(&buf[..n + 2]);
+    delay.delay_ms(POLL_MS);
+}
+
+// End of file