Herbert Graf wrote:

>      Well, I reduced the network to three devices, one at 145, one at 147
> and one at 159, they all respond with different temps, now say I physically
> remove the 145 and request data from 145, I get a response of all 1's and
> the DATAGOOD flag set,
> which is set if ack is 0, which is the way I understand it works,
> but without a device there shouldn't have been anything out there to pull
> the line low, just doesn't make sense. I am using 10K pullups. Could it be
> that I am going a distance? My I2C bus is about 10 meters (30 feet) long,
> all the devices work though, just the ack doesn't seem to. I am clocking out
> of a PC LPT port so I doubt the system is going to fast, but maybe that is
> it. It is not that serious, it just means that if a sensor is disconected I
> get a meaningless reading, but it does bug me. Thanks for any help. TTYL
> Net-Tamer V 1.11 - Test Drive

This is so simple, that I hesitate to bring it up, but it might help so I'll cha
nce it.

You say that you have reduced the network to three devices but when you pull the
 LM75 from
address 145 you are still detecting a LOW ACK (via the DATAGOOD flag being set)
when you do a
read, yes?  How about taking ALL the devices off of the network and see if you s
till are
detecting the ACK.  This would tell you if the line is actually being pulled LOW
 or your code
is somehow seeing a LOW when nothing is ACKing.  Perhaps you are doing one of th
ose
read-modify-write things?

Please excuse me if this is too simple or if I have missed something.

Michael

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