Rust DS3231, DS3232 and DS3234 Extremely Accurate Real-Time Clock Driver

This is a platform agnostic Rust driver for the DS3231, DS3232 and DS3234 extremely accurate real-time clocks, based on the embedded-hal traits.

This driver allows you to:

• Read and set date and time in 12-hour and 24-hour format. See: datetime.
• Read and set date and time individual elements. For example, see: year.
• Enable and disable the real-time clock. See: enable.
• Read the busy status. See busy.
• Read whether the oscillator is or has been stopped. See has_been_stopped.
• Clear the has-been-stopped flag. See clear_has_been_stopped_flag.
• Set and read the aging offset. See set_aging_offset.
• Select the function of the INT/SQW output pin. See use_int_sqw_output_as_interrupt.
• Alarms:
  • Set alarms 1 and 2 with several matching policies. See set_alarm1_day.
  • Set alarms 1 and 2 for a time. See set_alarm1_hms.
  • Read whether alarms 1 or 2 have matched. See has_alarm1_matched.
  • Clear flag indicating that alarms 1 or 2 have matched. See clear_alarm1_matched_flag.
  • Enable and disable alarms 1 and 2 interrupt generation. See enable_alarm1_interrupts.
• Wave generation:
  • Enable and disable the square-wave generation. See enable_square_wave.
  • Select the square-wave frequency. See set_square_wave_frequency.
  • Enable and disable the 32kHz output. See enable_32khz_output.
  • Enable and disable the 32kHz output when battery powered. See enable_32khz_output_on_battery.
• Temperature conversion:
  • Read the temperature. See temperature.
  • Force a temperature conversion and time compensation. See convert_temperature.
  • Set the temperature conversion rate. See set_temperature_conversion_rate.
  • Enable and disable the temperature conversions when battery-powered. See enable_temperature_conversions_on_battery.

The devices

This driver is compatible with the DS3231 and DS3232 I2C devices and the DS3234 SPI device.

These devices are low-cost temperature-compensated crystal oscillator (TCXO) with a very accurate, temperature-compensated, integrated real-time clock (RTC) including 236/256 bytes of battery-backed SRAM, depending on the model.

DS3231 and DS3232 details

The devices incorporate a battery input, and maintain accurate timekeeping when main power to the devices is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the devices as well as reduces the piece-part count in a manufacturing line. The devices are available in commercial and industrial temperature ranges, and are offered in a 16-pin, 300-mil SO package.

The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator. Two programmable time-of-day alarms and a programmable square-wave output are provided. Address and data are transferred serially through an I2C bidirectional bus.

A precision temperature-compensated voltage reference and comparator circuit monitors the status of VCC to detect power failures, to provide a reset output, and to automatically switch to the backup supply when necessary. Additionally, the RST pin is monitored as a pushbutton input for generating a μP reset.

DS3234 details

The DS3234 incorporates a precision, temperature-compensated voltage reference and comparator circuit to monitor VCC. When VCC drops below the power-fail voltage (VPF), the device asserts the RST output and also disables read and write access to the part when VCC drops below both VPF and VBAT. The RST pin is monitored as a pushbutton input for generating a μP reset. The device switches to the backup supply input and maintains accurate timekeeping when main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device as well as reduces the piece-part count in a manufacturing line. The DS3234 is available in commercial and industrial temperature ranges, and is offered in an industry-standard 300-mil, 20-pin SO package.

The DS3234 also integrates 256 bytes of battery-backed SRAM. In the event of main power loss, the contents of the memory are maintained by the power source connected to the V BAT pin. The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. Two programmable time-of-day alarms and a programmable square-wave output are provided. Address and data are transferred serially by an SPI bidirectional bus.

Datasheets:

• DS3231
• DS3232
• DS3234

Usage

To use this driver, import this crate and an embedded_hal implementation, then instantiate the appropriate device. In the following example an instance of the device DS3231 will be created. Other devices can be created with similar methods like: Ds323x::new_ds3234(...).

Please find additional examples using hardware in this repository: driver-examples

use ds323x::{DateTimeAccess, Ds323x, NaiveDate, Rtcc};
use linux_embedded_hal::I2cdev;

fn main() {
    let dev = I2cdev::new("/dev/i2c-1").unwrap();
    let mut rtc = Ds323x::new_ds3231(dev);
    let datetime = NaiveDate::from_ymd_opt(2020, 5, 1)
        .unwrap()
        .and_hms_opt(19, 59, 58)
        .unwrap();
    rtc.set_datetime(&datetime).unwrap();
    // do something else...
    let time = rtc.time().unwrap();
    println!("Time: {}", time);

    let _dev = rtc.destroy_ds3231();
}

Support

For questions, issues, feature requests like compatibility with other devices and other changes, please file an issue in the github project.

Minimum Supported Rust Version (MSRV)

This crate is guaranteed to compile on stable Rust 1.35 and up. It might compile with older versions but that may change in any new patch release.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contributing

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.