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'help with i2c -- maybe its timing'
1998\08\25@122433 by David Reinagel

picon face
Ryan,
       You just jarred something in my memory that might help.  I was trying
to us the LM78 to get readings over the I2C bus, and was getting no meaningful
data, and found out why when I call National.  Now I am not sure the LM75
has the same behavior, but it may.  It seams that in the LM78, they have a
state machine running to get samples, and if you start any I2C communication
when they are making a measure, they abandon the measurement, and you get what
every was the last reading they made.  Well, I was trying to interrogate the
LM78 every 100 milliseconds, and they was preventing it from even making one
measurement. To fix the problem, I had to change my logic so that I only tried
to make a reading once a second.  Then all my problems went away.  Hope this
helps you.

David Reinagel
Cisco Systems, Inc.


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1998\08\25@132347 by Ryan Pogge

flavicon
face
well I would almost want to try that except for 2 facts.

1) it works on a segmented led display  (I havent tried it but the author
has)
2) I always get the 9th bit no matter what.

so it reads the data and stores it correctly ?????
I think.
but maybee its not sending the data correctly?  maybee its the serial
routine thats not right..... its all I can think of.
so anyone who knows about interfaceing to a serial LCD should be able to
confirm if it is indeed correct.

it is an LM75cim-5 ...duno if that makes any difference... I think that is
just the packaging and it opperates on 5 volts...




>Ryan,
>        You just jarred something in my memory that might help.  I was
trying
>to us the LM78 to get readings over the I2C bus, and was getting no
meaningful
>data, and found out why when I call National.  Now I am not sure the LM75
>has the same behavior, but it may.  It seams that in the LM78, they have a
>state machine running to get samples, and if you start any I2C
communication
>when they are making a measure, they abandon the measurement, and you get
what
>every was the last reading they made.  Well, I was trying to interrogate
the
>LM78 every 100 milliseconds, and they was preventing it from even making
one
>measurement. To fix the problem, I had to change my logic so that I only
tried
>to make a reading once a second.  Then all my problems went away.  Hope
this
{Quote hidden}

george....
>> but I am gona go insane if I dont figure this out.
>>
>> It must be the way I am sending it to my serial LCD.  I duno.... george
said
{Quote hidden}

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