Hi all

I would want to install a DS3231 RTC on my RPI.

I have red the project from Exaga :

https://sarpi.fatdog.eu/index.php?p=chronodot-rtc

So I have tried to purchase a Chronot in an online shop.

This shop sends me an email saying that they cannot get Chronodot from Adafruit but saying that I can use this RTC available by Adafruit :

https://www.adafruit.com/product/3013

Is it true ? This product can be used for this project ?

Desiderius

Do you want a project (make your own clock module with soldering iron) or do you just want a clock for your Raspberry Pi computer?

If you just want a clock module ready to plug in, then some options:

Highly accurate: Adafruit PiRTC - Precise DS3231 (does NOT fit in official Raspberry Pi 4 case)
https://www.adafruit.com/product/4282

Cheaper: Adafruit PiRTC - PCF8523 (does NOT fit in official Raspberry Pi 4 case)
https://www.adafruit.com/product/3386

Smaller profile (fits in official Raspberry Pi 4 case): RasClock
(available at various online vendors - Amazon, PiShop etc)

Various other options out there, but the ones above I'm using and work well.

Hi Desiderius. I really don't know how I missed your post until now, as it's about one of my favourite ARM-related common topics... Real Time Clocks! <3

The "ChronoDot" is just a DS3231 controller chip mounted on a circular PCB and given a cheesy name. In essence it's no different to most other RTCs that feature the same chip. In order to connect this Adafruit RTC (I2C) to a Raspberry Pi you're going to find it just as easy as if it were a ChronoDot. So, yes this https://www.adafruit.com/product/3013 RTC can certainly be used - and dozens of other RTC like it or similar.

I have quiet a lot of different RTCs which I've used and tested on various ARM devices. The ones I favour most are DS3231-based which accommodate CR2032 button batteries - like this - because the forget-about-maintenance period is much greater in terms of battery capacity. Plus you can just change the battery if/when it does eventually drain. It's also possible to fit a rechargeable battery and power the RTC from the 5v pin (instead of the 3.3v pin) so you may never have to change the battery again. The DS3231 is designed to use anything from 3-5.5v if memory serves me correctly.

When selecting an appropriate RTC device for the raspberry Pi, just make sure it uses the I2C interface and has connectors for PWR (VCC), GND, SDA, SCL - those are the only 4 you need. My advice would always be to stay away from the DS1307 RTCs because they can be hit-and-miss affair when it comes to accuracy of keeping time. The DS3231 is vastly more accurate and generally drifts by just a few seconds a year - if that! All my running ARM devices have some form of DS3231-based RTC installed.

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Thanks for your answer @Exaga !

In the mean time, I have succedded to buy the ChronoDot !

SO I will follow the instructions of your tutorial

Hi Desiderius, the ChronoDot was the first RTC I bought for an ARM device - back in 2012 - because it seemed "fun to have to solder the pins on yourself" and plug it in, etc. Plus it had a replaceable battery and so fit my needs perfectly. Through time I've learned that in terms of build-quality it's one of the best, compared to most alternatives, and performance is comparable with other DS3231SN RTCs which you would expect. For sure, the DS3231 controller chip is consistently accurate.

The ChronoDot-RTC guide to install it needs updating, as it's been around for a few years and was designed around the RPi (1). However, it will enable you to install and configure the system to use the RTC on any Raspberry Pi device running Slackware ARM. Once you've done it with the ChronoDot, it's pretty much the same procedure for other RTCs. So you can practically buy any I2C RTC to use with your Slackware ARM devices.

I hope you have lots of fun.

Take a look at this photo of one of my more adventurous RTC solutions...

https://imgur.com/mfw7JO5

Just an example of applying a little D.I.Y. for when the battery on these cheap RTCs finally dies. I didn't want to give this one up because it's a great timekeeper!

This RTC is still working perfectly in one of my Raspberry Pis.

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As a follow-up to the DS3231 "ChronoDot". This RTC advertises that "the CR1632 battery should maintain timekeeping for 8 years."

I'm very pleased to say the advertising claims are quite accurate. It's been almost 8 years exactly since I purchased the ChronoDot real time clock, and I have used it on quite a few ARM devices during that time. Over the past few days I've noticed this RTC has not been keeping accurate time. So a new CR1632 has been installed, which is the first change of battery since it was first used early in 2013.

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