# ds3231

Maxim DS3231 RTC driver on [libavr](https://git.blackmark.me/avr/libavr):
clock and alarm read/write, alarm interrupts, oscillator-stop detection,
die temperature. One source runs on every libavr chip — TWI hardware on
the mega328P, open-drain software I2C on the tinies. All bus errors
surface as `std::expected`.

```cpp
using bus = dev::i2c<{.frequency = 100_kHz}>;
using rtc = ds3231::device<bus>;

auto now = rtc::read_clock();       // result<date_time>
(void)rtc::set_alarm1({}, ds3231::alarm1_rate::once_per_second);
```

`example/main.cpp` is the full tour. Build with a libavr checkout:

```sh
LIBAVR_ROOT=/path/to/libavr cmake --preset attiny85-generated
cmake --build --preset attiny85-generated
```

Presets cover attiny85/atmega328p in both libavr modes (generated and
reflect). The legacy yazoalfa-based driver lives on the `master` branch.

Differences from legacy: weekday-rate alarms now actually set the DY bit
(the old `setAlarmHelper` always cleared it), reads/writes are single
coherent bus transactions, and errors are reported instead of ignored.