Introduction to the DS1302 Real Time Clock (RTC) Library
The DS1302 is a small battery-backed real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed, or if the power is lost. This is perfect for clocks, datalogging, timers, etc. The DS1302 also features a trickle charger for the battery so you never need to change batteries.
The DS1302 is simple and inexpensive but not a high precision device. It may lose or gain up to two seconds a day. In addition, it communicates over a custom serial protocol. For a high-precision, temperature compensated, alternative, please check out the DS3231 precision RTC, which communicates over I2C.
Dependencies
This driver depends on:
Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle or individual libraries can be installed using circup.
Installing from PyPI
On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:
pip3 install circuitpython-ds1302
To install system-wide (this may be required in some cases):
sudo pip3 install circuitpython-ds1302
To install in a virtual environment in your current project:
mkdir project-name && cd project-name
python3 -m venv .venv
source .env/bin/activate
pip3 install circuitpython-ds1302
Installing to a Connected CircuitPython Device with Circup
Make sure that you have circup installed in your Python environment.
Install it with the following command if necessary:
pip3 install circup
With circup installed and your CircuitPython device connected use the
following command to install:
circup install ds1302
Or the following command to update an existing version:
circup update
Usage Example
Basics
Of course, you must import the library to use it:
import time
import board
import ds1302
The DS1302 requires three pins: Reset, I/O, and Clock. These can be any 3 pins as long as they support digital output (and in the case of I/O, digital input):
import board
reset_pin = board.GP13
io_pin = board.GP14
clock_pin = board.GP15
Now, you can use these pins to instantiate the RTC object:
rtc = ds1302.DS1302(reset_pin, io_pin, clock_pin)
To set the time, you need to set datetime to a time.struct_time object:
rtc.datetime = time.struct_time((2026, 7, 16, 12, 38, 0, 3, -1, -1))
After the RTC is set, you retrieve the time by reading the datetime
attribute and access the standard attributes of a struct_time such as tm_year,
tm_hour and tm_min.
t = rtc.datetime
print(t)
print(t.tm_hour, t.tm_min)
Documentation
API documentation for this library can be found on Read the Docs.
For information on building library documentation, please check out this guide.
Contributing
Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.
Table of Contents
API Reference