Hi Jason:
For removing some noises in I2C , try to connect a parallel connection as I
indicated in an attached file ( an ORCaD archive ).
Please if u succeded to solve that way give me a notice or otherwise I would
like to continue proposing  another way.
Regards,
_______________________________
Ismael M. Khangane ( Digital Designer )
IAI-CSIC    Madrid, Spain.
ismaelm@iai.csic.es
_______________________________


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Jason Wolfson escribis:

> Gentlemen,
> I've got a PIC reading a National Semi LM75 I2C temp sensor and
> I'm seeing the LM75 lock up with some induced noise from the relays
> I'm controlling externally.
>
> The relays are not part of my design so I can't quite them down.
> I've put 330 ohm series resistors in the SDA and SCL lines and it
> helps but doesn't cure the problem.
>
> The temp sensor is on another board connected by a 6 ft telephone cord and
> RJ11 connectors.
>
> Does Vcc need a series resistor? A Zener? A TVS diode? On SDA & SCL?
>
> Thanks
> Jason Wolfson
>  Lipidex Corp
>  50 Franklin Terrace
>  Duxbury MA 02332
>
>   781-834-1600
>   781-834-1601 FAX
>
> jason@lipidex.com