Real time clocks ('RTC's) for the RPi - so many available

I am interested in adding a real time clock (RTC) to the RPi. Core Electronics has so many RTC clocks available for sale at Core. Search for real time clock and there are 26 results. I have found the following features.

  • breakout - all the boards seem to be breakout.
  • communication to and from breakout - SPI, Are there IIC?
  • button battery or running from the 5V or 3,3V supply - do all the RTC breakout boards have provision for a button battery? Or in other words, when the 5V or 3.,3 is off, do all breakout RTCs go to the button battery OR is it only some RTCs have provision for a button battery?
  • accuracy - which are the least accurate and which are the most accurate

Please assist,
Thank you,

Hi Anthony,

Before I go into all your questions, this Raspberry Pi RTC is a “Maker Favourite” which means that of all the similar devices this is the one that we recommend:

If there is not a provision for a button battery they will still need external power or they will stop keeping time when the RPI is off.

They are available in different accuracies. This model is higher accuracy, and still a Maker Favourite:

I hope that helps! Let us know how your project works out!

Dear Stephen,
Thank you for your reply.
One question, on communications protocol. Do they employ SPI or IIC or both?
Thank you,
Anthony of Sydney

Hi Anthony,

They are both I2C only.

I have just purchased a RTC module: DS1307 for my Pi 3 Model B. I have installed the RTC but when I do a sudo i2cdetect -y 1 I get no recognition of the new RTC. I have i2c-tools installed
What can I do?

Hi Harry,

Have you followed the setup instructions in the product Wiki?