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DS3231 I2C Real Time Clock

This article illustrate how to use the Az-Delivery Real Time Clock RTC DS3231 I2C module with the CM-Home

Wirings

These are the signal wirings between the AZ-Delivery Real Time Clock (RTC) DS3231 module and the Grove port on the CM-Home board.

Home Pin # Home signal Az signal
1 SCL (GPIO45) SCL
2 SDA (GPIO44) SDA
3 3V3 VCC
4 GND GND

config.txt

Add these lines to /boot/firmware/config.txt file:

# Set the I2C1 on GPIO 44 and GPIO 45 pins
dtoverlay=i2c1,pins_44_45
dtoverlay=i2c-rtc,ds3231

then reboot the Raspberry Pi.

Check if the kernel has detected the RTC chip:

$dmesg | grep -i rtc
[    2.015759] rtc-ds1307 1-0068: registered as rtc0
[    2.021607] rtc-ds1307 1-0068: setting system clock to 2025-03-24T23:53:18 UTC (1742860398)

Read the time from the RTC chip:

$ sudo hwclock --show
2025-03-25 01:01:36.704186+01:00

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