Ds1302 with backup power supply
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Hi everyone. I'm using a BS2 with a ds1302 time chip. In the
example from parallax's web site it states that this chip can be
powered with a cap to retain its time setting. The problem is that
when the circuit loses power and then regains power, the stamp starts
its program from the begining where it intializes the ds1302 with a
certain time. Is there any way for the stamp to detect if the cap
has a charge on it, skip the step that intializes the ds1302 and just
read the present time from the chip.
Thanks,
Charlie
example from parallax's web site it states that this chip can be
powered with a cap to retain its time setting. The problem is that
when the circuit loses power and then regains power, the stamp starts
its program from the begining where it intializes the ds1302 with a
certain time. Is there any way for the stamp to detect if the cap
has a charge on it, skip the step that intializes the ds1302 and just
read the present time from the chip.
Thanks,
Charlie
Comments
power. Might try finding out what this is and check it when your program
starts.
On a side note, we've got a Dallas chip on one of our pieces of equipment at
work, and it uses a 3v coin cell for power -- lasts about 2 years.
Original Message
> Hi everyone. I'm using a BS2 with a ds1302 time chip. In the
> example from parallax's web site it states that this chip can be
> powered with a cap to retain its time setting. The problem is that
> when the circuit loses power and then regains power, the stamp starts
> its program from the begining where it intializes the ds1302 with a
> certain time. Is there any way for the stamp to detect if the cap
> has a charge on it, skip the step that intializes the ds1302 and just
> read the present time from the chip.
>
> Thanks,
>
> Charlie
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Here are 2 ways I've done to get around this:
1) Have a seperate program that just sets the time. Run this, set
time, then download your real program.
2) Once time is set, write a value to a memory location. This will
remain even if power is lost (EEPROM). Before setting time, check
this memory location to see if has been set yet or not. If not, set
time, if set, skip set time.
3) One more option is to get time serially from a com port on a PC,
a simple program to write out time in Qbasic serially. Then you have
a way to update it when you need to. An overkill of this and much
more is done with out BISCIT programs if you need some code to look
at.
http://www.selmaware.com/biscit
-Martin Hebel
Southern Illinois University Carbondale
Electronics Systems Technologies
http://www.siu.edu/~imsasa/elm
SelmaWare Solutions
[url=Http://www.selmaware.com/s-plot]Http://www.selmaware.com/s-plot[/url]
--- In basicstamps@y..., charlieb83@h... wrote:
> Hi everyone. I'm using a BS2 with a ds1302 time chip. In the
> example from parallax's web site it states that this chip can be
> powered with a cap to retain its time setting. The problem is that
> when the circuit loses power and then regains power, the stamp
starts
> its program from the begining where it intializes the ds1302 with a
> certain time. Is there any way for the stamp to detect if the cap
> has a charge on it, skip the step that intializes the ds1302 and
just
> read the present time from the chip.
>
> Thanks,
>
> Charlie