# DS3231 I2C Real Time Clock 

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

<img src="./ds3231.jpg" class="img-responsive">

## 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

### Links

* @article='cmhome_grove'
* [Az-Delivery DS3231 eBook](https://cdn.shopify.com/s/files/1/1509/1638/files/AZ081_A_3-9_EN_B01M2B7HQB_07c22e20-7990-485f-aebb-edba5f1c47ff.pdf?v=1721038618)
* [Az-Delivery DS3231 product page](https://www.az-delivery.de/en/products/ds3231-real-time-clock)
* <https://github.com/raspberrypi/linux/blob/rpi-4.9.y/arch/arm/boot/dts/overlays/README#L783>

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@include='adv_cmpanel'