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Topic: Interfacing RTC BQ3287 (Read 1 time) previous topic - next topic


Hello people,

i started working with a RTC BQ3287 and connected it like in the project from http://fritzing.org/projects/ibm-rtc-on-arduino/
after starting it up by sending 'i' via the Serial console and it starts counting seconds and works perfect. According to the manual,
the 3287 series contains already a backup battery. if i disconnect my arduino from power source and reconnect it after some minutes,
it holds the Time, but if it is disconnected for more then 2 hours,
i have to reinitialize the clock and set the time again.
Do I have to set anything in the Clock, or is my english so bad, that i missunderstood something in the manual?

Best Regards, Martin


The art of getting good answers lies in asking good questions.


Thanks for your Response.
In my opinion, it says in the manual, it has a builtin battery for backup. I dont have pins to connect a second power source for backup.


Do you have a link to the RTC that you have? If it has a battery backup, the battery should be replaceable. What do the makers expect you to do when the battery goes dead?
The art of getting good answers lies in asking good questions.


Hi Paul,
the link to the datasheet is http://focus.ti.com/lit/ds/symlink/bq3287.pdf
It says:
"The bq3287 is functionally equivalent
to the bq3285, except that the
battery (16, 20) and crystal (2, 3)
pins are not accessible. These pins
are connected internally to a coin
cell and quartz crystal. The coin cell
is sized to provide 10 years of data
retention and clock operation in the
absence of power."
This means for me, that if my arduino is powered down, the RTC is still counting his seconds up.

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