Real Time Clock (RTC) for RasPi

Former Member over 12 years ago

Has anyone done and RTC for the pi, or know of a link for more info on implementing one?

Many thanks.

morgaine over 12 years ago

Hi Brian.

You're in luck -- Drew wrote up a nice blog post about exactly that -- http://www.element14.com/community/groups/raspberry-pi/blog/2012/07/19/what-time-is-it-adding-a-rtc-to-the-raspberry-pi-via-i2c
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Former Member over 12 years ago in reply to morgaine

Brilliant, Thanks Morgaine!
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jamodio over 12 years ago in reply to Former Member

I'm about to test something similar using Microchip's MCP79411.

I'l write a little article when I'm done and post the link.

-J
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morgaine over 12 years ago in reply to jamodio
@jamodio: Excellent, I don't know the device so I looked it up, links in case someone needs:

Product page -- http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en550283
Datasheet -- http://ww1.microchip.com/downloads/en/DeviceDoc/22266D.pdf

Looking forward to the article!

@Brian: Forum contributors write useful blog articles like that one quite frequently. I'm maintaining a list of Element 14 Blog entries at the top of the following forum thread. If you're considering projects, it may be useful to check the list occasionally:

http://www.element14.com/community/thread/19133?tstart=0
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Former Member over 12 years ago in reply to jamodio

That would be nice, thanks jamodio
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Former Member over 12 years ago in reply to Former Member

I also found these PIC boards which may also work with Pi?

http://www.mikroe.com/eng/categories/view/38/time-measuring-boards/
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morgaine over 12 years ago in reply to Former Member
Nice list of boards there, thanks Brian. I'll keep an eye out for MikroElektronika in future.

They seem to use two different RTC devices in their boards:

NXP PCF8583P/F5,112PCF8583P/F5,112              -- http://www.nxp.com/search?q=pcf8583&type=keyword
Maxim/Dallas DS1307 -- http://www.maxim-ic.com/datasheet/index.mvp/id/2688/t/al

It might be of interest that Adafruit links to Drew's article for Pi timekeeping (Drew used two of their products):

Drew's blog post (repeated)           -- http://www.adafruit.com/blog/2012/07/19/raspberry-pi-what-time-is-it-how-to-add-an-adafruit-rtc-to-the-raspberry-pi-via-i2c/
Adafruit's DS1307 breakout board -- http://adafruit.com/products/264
Adafruit's logic level converter       -- https://www.adafruit.com/products/757

Morgaine.
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jamodio over 12 years ago in reply to Former Member

They should work Brian, I used the PCF8583P/F5,112PCF8583P/F5,112 before talking to a PIC18F97J60 and didn't have any problems to make it work. Getting the board instead of the parts saves you the work of trying to find the right crystal and capacitors to use, sometimes those crystals and the RTC cirtuits are very picky to get working.

One detail to take in account with the Microchip part (I don't recall being necessary on the NXP part) is that before the internal clock for the oscillator to start working you need first to initialize the device, by default the oscillator is OFF.

-J
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Former Member over 12 years ago in reply to jamodio

Thanks again, perhaps now I have too many options
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fustini over 12 years ago in reply to Former Member

The downside of the DS1307 for the Pi is that it requires a logic level converter as it runs at 5V and the Pi is 3.3V logic. If you don't already have logic level converters, then I'd recommend going with a RTC that can operate at 3.3V (such as the PCF8583P/F5,112PCF8583P/F5,112 or MCP79411 mentioned above).
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