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'[PIC] Read 1-Wire (iButton)'
2011\01\08@080457 by Robert Csaba Molnar

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I'm trying to read a 64 bit ID out on an iButton. The iButton is connected to ground and  and a   CN(change notification) pin.  If the iButton is discharged CN is triggered correctly.
I start having problems when trying to read the iButton several times in a short period of time (connect/disconnect the iButton). The CN does not trigger the interrupt in this case.

I suspect that the iButton is not completely discharged so when the iButton is connected ,the change is to small for the PIC to notice it.

Has anyone experienced this problem? 
As a last resort I can use a timer and try to read the button regardless if it's there or not, but I do not want to waste cpu cycles on this if there is another way to do it.

Kind Regards,
Rober

2011\01\08@134510 by John Temples

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part 1 781 bytes content-type:text/plain; charset="iso-8859-15" (decoded quoted-printable)

On Sat, 8 Jan 2011, Robert Csaba Molnar wrote:

> I start having problems when trying to read the iButton several times
> in a short period of time (connect/disconnect the iButton). The CN
> does not trigger the interrupt in this case.
>
> I suspect that the iButton is not completely discharged so when the
> iButton is connected ,the change is to small for the PIC to notice it.
>
> Has anyone experienced this problem? 

Yes, it's a known issue with the iButton.

> As a last resort I can use a timer and try to read the button
> regardless if it's there or not, but I do not want to waste cpu cycles
> on this if there is another way to do it.

That's the usual solution.

--
John W. Temples, III

part 2 181 bytes content-type:text/plain; name="ATT00001.txt"
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