I2C off board distances

> Here's a photo of that HVAC controller:
>
> http://www.synthcom.com/~nb/Controller3.jpg
>
> Yes, I'm aware that the power supply is a big ugly hack. ;-) It has since
> been replaced with a switcher...
>
> -->Neil
>
Hi Neil,
I think the link you meant was:
http://www.synthcom.com/~nb/controller3.jpg
(lower case "c")
The Fry's receipt makes it look so much more real ;-)

PS: several of your stinky pics don't show up... is the images directory in
the right place?

Bob

"Bob" <SkiBoyBob@excite.com> wrote in message 
news:10kma2ff3su2o80@corp.supernews.com...
>> Here's a photo of that HVAC controller:
>> http://www.synthcom.com/~nb/Controller3.jpg
>> Yes, I'm aware that the power supply is a big ugly hack. ;-) It has since
>> been replaced with a switcher...
> Hi Neil,
> I think the link you meant was:
> http://www.synthcom.com/~nb/controller3.jpg

No! I meant:

http://www.synthcom.com/~nb/controller3.JPG

> PS: several of your stinky pics don't show up... is the images directory 
> in
> the right place?

That whole directory is a cobwebsite ....

-->Neil 

Colin MacDougall <colin@blueyonder.co.uk> wrote:
: Has anyone any experience of running an I2C bus from
: a PCB to a remote I2C device ? I am thinking of
: connecting a remote Dallas Semiconductor I2C temperature
: sensor IC to a micro over a length of 4 or 5 metres of
: wire. The temp sensor would be fixed to the ceiling to
: measure room temperature and the micro would be in a
: monitoring / control box on the wall.

: Could I run this at the typical 400 KHz clock speed with
: a decent bit of screened cable ?

The Dallas/Maxium 1 wire interface is more suited for this. You can use a i2c 
to 1wire interface that Maxium just released and use a 18S20 1 wire temp
sensor. They make a RS232 to 1 wire interface also. 

1 wire info: http://www.1wire.org/ and http://www.maxim-ic.com/

I have a 60' or so cable run to several of my weather sensors at home that
uses the 1 wire interface.

See:
http://pages.sbcglobal.net/greghol/wx/weather.html

-- 
Greg Holdren
greg (dot) holdren (at) <initials of company> (dot) com

Colin MacDougall wrote:

> Has anyone any experience of running an I2C bus from
> a PCB to a remote I2C device ? I am thinking of
> connecting a remote Dallas Semiconductor I2C temperature
> sensor IC to a micro over a length of 4 or 5 metres of
> wire. The temp sensor would be fixed to the ceiling to
> measure room temperature and the micro would be in a
> monitoring / control box on the wall.
>
> Could I run this at the typical 400 KHz clock speed with
> a decent bit of screened cable ?
>
> Colin

Look at the USB specs (USB.org)  the USB protocol is built on top of
I2C.
By the way SM Bus is too, but I don not think that is designed to go off
board very far.

Neil Kurzman <nsk@mail.asb.com> wrote:
> Colin MacDougall wrote:

[...]
> > sensor IC to a micro over a length of 4 or 5 metres of
[...]

> Look at the USB specs (USB.org)  the USB protocol is built on top of
> I2C.

... and has a maximum allowed cable length of 5 meters between active
components.  Which likely means that it's unsuitable for the case at
hand.

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

USB is not based on I2C. USB has unique electrical and protocol 
characteristics invented for USB.

"Neil Kurzman" <nsk@mail.asb.com> wrote in message 
news:414C515B.AE18C2D4@mail.asb.com...
>
>
> Colin MacDougall wrote:
>
>> Has anyone any experience of running an I2C bus from
>> a PCB to a remote I2C device ? I am thinking of
>> connecting a remote Dallas Semiconductor I2C temperature
>> sensor IC to a micro over a length of 4 or 5 metres of
>> wire. The temp sensor would be fixed to the ceiling to
>> measure room temperature and the micro would be in a
>> monitoring / control box on the wall.
>>
>> Could I run this at the typical 400 KHz clock speed with
>> a decent bit of screened cable ?
>>
>> Colin
>
> Look at the USB specs (USB.org)  the USB protocol is built on top of
> I2C.
> By the way SM Bus is too, but I don not think that is designed to go off
> board very far.
>
>