Main struct

In this section, we will define the main struct for our driver and implement main I2C communication that will let us interact with the RTC hardware.

#![allow(unused)]
fn main() {
pub const DEFAULT_BASE_CENTURY: u8 = 20;

pub struct Ds3231<I2C> {
    i2c: I2C,
    pub(crate) base_century: u8,
}
}

Unlike the DS1307, this driver struct has one more field. The base_century field lets users set which century the year represents. For example, if users want the year 25 to mean 2125 instead of 2025, they can change the base century.

Implement the RTC HAL's ErrorType

Next, we will implement the ErrorType trait from RTC HAL to specify what error type our driver will use.

#![allow(unused)]
fn main() {
impl<I2C: embedded_hal::i2c::I2c> rtc_hal::error::ErrorType for Ds3231<I2C> {
    type Error = crate::error::Error<I2C::Error>;
}
}

Implement Ds3231

We will start implementing the DS3231 driver with its core functionality. This implementation block will contain all the methods we need to interact with the RTC chip.

Note: Any other methods we explain after this in this section all go into the same impl block shown below.

#![allow(unused)]
fn main() {
impl<I2C, E> Ds3231<I2C>
where
    I2C: embedded_hal::i2c::I2c<Error = E>,
    E: core::fmt::Debug,
{
    pub fn new(i2c: I2C) -> Self {
        Self {
            i2c,
            base_century: DEFAULT_BASE_CENTURY,
        }
    }

    pub fn set_base_century(&mut self, base_century: u8) -> Result<(), Error<E>> {
        if base_century < 19 {
            return Err(Error::InvalidBaseCentury);
        }
        self.base_century = base_century;
        Ok(())
    }

    pub fn release_i2c(self) -> I2C {
        self.i2c
    }
}
}

We use a default base century of 20 and provide a set_base_century function in case users want to change the base century.