Imported from GitHub: skiselev/rpi_rtc_ds3231 · commit e242486 · license GPL-3.0

Description

Maxim DS3231 Based RTC Module for Raspberry Pi

README

RPi DS3231 RTC

Maxim DS3231 Based RTC Module for Raspberry Pi

Introduction

This is a real-time clock (RTC) module for Raspberry Pi and Raspberry Pi Zero. The module is similar to Adafruit PiRTC, but uses the highly accurate Maxim Integrated DS3231 RTC IC with an integrated temperature-compensated crystal oscillator, and more common CR2032 battery.

Hardware Documentation

Schematic and PCB Layout

Bill of Materials

RPi DS3231 RTC project on Mouser.com - View and order all components except of the PCB.

RPi DS3231 RTC on OSH Park - View and order the PCB.

Component type	Reference	Description	Quantity	Possible sources and notes
PCB		RPi DS3231 RTC PCB - Version 1.0	1	Order from OSH Park
Integrated Circuit	U1	Maxim DS3231	1	Mouser 700-DS3231S#T&R-
Capactior	C1	0.1uF, 0603	6	Mouser 77-VJ0603Y104JXJPBC
Resistor	R1	10 kohm, 0603	1	Mouser 71-CRCW060310K0FKEB
Connector	P1	3x2, 2.54 mm, socket	1	Mouser 517-929852-01-03-RA
Battery Holder	BT1	CR2032 Battery Holder	1	Mouser 712-BAT-HLD-001-THM
Battery	BT1	CR2032	1	Mouser 658-CR2032

Software Documentation

Raspbian Configuration

The following steps assume that you have a fairly new Rapbian distribution installed and running on your Rapsberry Pi, and that RPi DS3231 RTC module is plugged into the Raspberry Pi.

Enable I2C Support

Run raspi-config:

$ sudo raspi-config

Navigate to the Interfacing Options menu. If this menu is missing (on older Raspbian versions), try the Advanced Options menu instead. Next, select the I2C menu, and answer Yes to Would you like the ARM I2C interface to be enabled? and Would you like the I2C kernel modules to be loaded by default? questions.

Reboot the system

Verify that RTC Module Is Detected

Install i2c-tools package:

$ sudo apt-get install i2c-tools

Run i2cdetect -y 1 command and verify that the I2C device is detected at address 0x68:

$ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Enable Kernel Support for DS3231 RTC

Open /boot/firmware/config.txt in your favorite editor (nano, vi) as root. For example:

$ sudo nano /boot/firmware/config.txt

Add the following lines at the end of the file:

# Enable DS3231 RTC
dtoverlay=i2c-rtc,ds3231

Remove fake-hwclock package:

$ sudo apt-get -y remove fake-hwclock
$ sudo update-rc.d -f fake-hwclock remove

Enable setting up system time to the RTC time at boot. Open /lib/udev/hwclock-set in your favorite editor:

$ sudo nano /lib/udev/hwclock-set

And comment out the following lines:

#if [ -e /run/systemd/system ] ; then
# exit 0
#fi

Also comment the following line(s):

#/sbin/hwclock --rtc=$dev --systz --badyear
#/sbin/hwclock --rtc=$dev --systz

Save the file, and reboot the system

Setting and Reading the RTC time from Command Line

• Use hwclock -w command to set the RTC time to the system time. You can use date command to set and verify the system time prior to writing it to the RTC.
• Use hwclock --set --date=<date_string> command to set the RTC time to the time given by <date_string>
• Use hwclock -r command to read the time from the RTC