klips/esp/rust/03_aht20/src/main.rs

#![no_std]
#![no_main]

/// Represents a reading from the sensor.
pub struct SensorReading<T> {
    pub humidity: T,
    pub temperature: T,
}

/// Possible errors when interacting with the sensor.
#[derive(Debug)]
pub enum SensorError {
    ChecksumMismatch,
    Timeout,
    PinError,
}

pub struct Dht20<I: I2cEmbedded, D: DelayNs> {
    pub i2c: I,
    pub delay: D,
}

impl<I: I2cEmbedded, D: DelayNs> Dht20<I, D> {
    const SENSOR_ADDRESS: u8 = 0x38;

    pub fn new(i2c: I, delay: D) -> Self {
        Self { i2c, delay }
    }

    pub fn read(&mut self) -> Result<SensorReading<f32>, SensorError> {
        // Check status
        let mut status_response: [u8; 1] = [0; 1];
        let _ = self
            .i2c
            .write_read(Self::SENSOR_ADDRESS, &[0x71], &mut status_response);

        // Calibration if needed
        if status_response[0] & 0x18 != 0x18 {
            let _ = self.i2c.write(Self::SENSOR_ADDRESS, &[0x1B, 0, 0]);
            let _ = self.i2c.write(Self::SENSOR_ADDRESS, &[0x1C, 0, 0]);
            let _ = self.i2c.write(Self::SENSOR_ADDRESS, &[0x1E, 0, 0]);
        }

        // Trigger the measurement
        self.delay.delay_ms(10);
        let _ = self.i2c.write(Self::SENSOR_ADDRESS, &[0xAC, 0x33, 0x00]);

        // Read the measurement status
        self.delay.delay_ms(80);
        loop {
            let mut measurement_status_response: [u8; 1] = [0; 1];
            let _ = self
                .i2c
                .read(Self::SENSOR_ADDRESS, &mut measurement_status_response);
            let status_word = measurement_status_response[0];
            if status_word & 0b1000_0000 == 0 {
                break;
            }
            self.delay.delay_ms(1);
        }

        // Read the measurement (1 status + 5 data + 1 crc)
        let mut measurement_response: [u8; 7] = [0; 7];
        let _ = self
            .i2c
            .read(Self::SENSOR_ADDRESS, &mut measurement_response);

        // Humidity 20 bits (8 + 8 + 4)
        let mut raw_humidity = measurement_response[1] as u32;
        raw_humidity = (raw_humidity << 8) + measurement_response[2] as u32;
        raw_humidity = (raw_humidity << 4) + (measurement_response[3] >> 4) as u32;
        let humidity_percentage = (raw_humidity as f32 / ((1 << 20) as f32)) * 100.0;

        // Temperature 20 bits
        let mut raw_temperature = (measurement_response[3] & 0b1111) as u32;
        raw_temperature = (raw_temperature << 8) + measurement_response[4] as u32;
        raw_temperature = (raw_temperature << 8) + measurement_response[5] as u32;
        let temperature_percentage = (raw_temperature as f32 / ((1 << 20) as f32)) * 200.0 - 50.0;

        // Compare the calculated CRC with the received CRC
        let data = &measurement_response[..6];
        let received_crc = measurement_response[6];
        let calculated_crc = Self::calculate_crc(data);
        if received_crc != calculated_crc {
            return Err(SensorError::ChecksumMismatch);
        }

        Ok(SensorReading {
            humidity: humidity_percentage,
            temperature: temperature_percentage,
        })
    }

    fn calculate_crc(data: &[u8]) -> u8 {
        let polynomial = 0x31u8; // x^8 + x^5 + x^4 + 1
        let mut crc = 0xFFu8;

        for &byte in data {
            crc ^= byte;
            // CRC8 - process every bit
            for _ in 0..8 {
                if crc & 0x80 != 0 {
                    crc = (crc << 1) ^ polynomial;
                } else {
                    crc <<= 1;
                }
            }
        }

        crc
    }
}

use embedded_hal::{delay::DelayNs, i2c::I2c as I2cEmbedded};
use esp_backtrace as _;
use esp_hal::{
    clock::CpuClock,
    delay::Delay,
    gpio::{Level, Pull},
    i2c::master::I2c,
    xtensa_lx_rt::entry,
};
use fugit::{ExtU64, HertzU32};

#[entry]
fn main() -> ! {
    let peripherals = esp_hal::init(esp_hal::Config::default());
    esp_println::logger::init_logger_from_env();
    let mut delay = Delay::new();

    // TODO: Remove unwrap
    let i2c_for_dht20 =
        esp_hal::i2c::master::I2c::new(peripherals.I2C0, esp_hal::i2c::master::Config::default())
            .unwrap()
            .with_sda(peripherals.pins.gpio21)
            .with_scl(peripherals.pins.gpio22);
    let mut dht20 = Dht20::new(i2c_for_dht20, delay);

    loop {
        delay.delay_ms(5000);
        match dht20.read() {
            Ok(sensor_reading) => log::info!(
                "DHT 20 Sensor - Temperature: {} °C, humidity: {} %",
                sensor_reading.temperature,
                sensor_reading.humidity
            ),
            Err(error) => log::error!("An error occurred while trying to read sensor: {:?}", error),
        }

        log::info!("-----");
    }
}