#rtc #clock #driver #embedded-hal-driver #pcf8563

no-std pcf8563

Platform-agnostic Rust driver for the NXP PCF8563 real-time clock

2 releases

0.1.2 Oct 17, 2021
0.1.1 Jul 21, 2021
0.1.0 Apr 17, 2021

#147 in Embedded development

47 downloads per month


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Rust PCF8563 Real-Time Clock Driver

Maintenance Intention

A platform agnostic Rust driver for the NXP PCF8563 real-time clock, based on the embedded-hal traits.

Based on this RTC driver

This driver allows you to:

  • Read and set date and time. See: get_datetime and set_datetime
  • Set only the time (HH:MM:SS) for clock applications without the calendar function
  • Read and set the alarm minutes, hours, day and weekday
  • Enable the alarm components separately
  • Disable the alarm components separately or all at once
  • Set the timer and timer frequency
  • Set clock output frequency and enable/disable clock output
  • Enable and disable alarm interrupt and timer interrupt
  • Read and set various other control functions


  • test with other MCUs
  • add get_timer_frequency function
  • add get_timer_interrupt_mode function
  • add get_clkout_frequency function
  • add an nRF example

How this driver was won written

The device

The PCF8563 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption. A programmable clock output, interrupt output, and voltage-low detector are also provided. All addresses and data are transferred serially via a two-line bidirectional I2C-bus. Maximum bus speed is 400 kbit/s. The register address is incremented automatically after each written or read data byte.

Provides year, month, day, weekday, hours, minutes, and seconds based on a 32.768 kHz quartz crystal.

  • Century flag
  • Low backup current
  • Programmable clock output for peripheral devices (32.768 kHz, 1.024 kHz, 32 Hz, and 1 Hz)
  • Alarm and timer functions
  • Open-drain interrupt pin

Datasheet: PCF8563


To use this driver, import this crate and an embedded_hal implementation, then instantiate the device.

Please find additional examples using hardware in this repository: examples


use cortex_m;
use cortex_m_rt::entry;
use panic_halt as _;
use stm32l4xx_hal::{
    serial::{Config, Serial},

use pcf8563::*;

use core::fmt::Write;

fn main() -> ! {
    let cp = cortex_m::Peripherals::take().unwrap();
    let dp = stm32l4xx_hal::stm32::Peripherals::take().unwrap();

    // set up the flash, reset & clock control, and power control
    // set up the clocks    
    // set up GPIO ports
    // set up LED for some blinking
    // set up USART
    // get the delay provider    
    // set up I2C bus
    // set up the PCF8563 device
    let mut rtc = PCF8563::new(i2c); 

    // prepare date and time to be set
    let now = DateTime {
        year: 21, // 2021
        month: 4, // April
        weekday: 0, // Sunday
        day: 4, 
        hours: 16,
        minutes: 52,
        seconds: 00,

    // set date and time in one go

    loop {
        delay.delay_ms(500 as u32);
        //get date and time in one go
        let time = rtc.get_datetime().unwrap();

        writeln!(tx, "{:02}/{:02}/{:02} {:02}:{:02}:{:02} day {}\r", 
                time.year, time.month, time.day, 
                time.hours, time.minutes, time.seconds,

        delay.delay_ms(500 as u32);



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


Licensed under either of


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.