Hi!
I feel a strong need for a i2c newsgroup, webpage or yahoo group. Exists?
All the webpages I know a very limited in parts to the subject i2c.

82B96 background info from Philips is here (interesting as they show other
vendors circuits and historical info)
http://my.semiconductors.philips.com/acrobat/other/mcu/notes_82b96.pdf
Yes, I think the 82B96 doesn't know anything about the protocol. As I
understand it the device works by sensing a differential voltage between
external and internal signal. The Philips block diagram shows voltage
sources of 0.6 volts in-line (= diodes?).

Surely.
The Philips 82B96 does isolation for i2c with a little help. What you
describe is more like Ethernet or other "networks".
You can directly add chips to the bus and that is the benefit of i2c.

We speak about i2c ! Having the benefit of directly interface to a mass of
different chips. Current loops is another field.

Tauno Voipio wrote:
> 
> "Jacek R. Radzikowski" <jacek+maqmba@spamer.die.die.die.piranet.org> wrote
> in message news:bs4ltb$mki$1@www.itl.waw.pl...
> > Tauno Voipio <tauno.voipio@iki.fi.spambait_remove.invalid> wrote:
> >
> > > "Henry" <otc_friend@gmx.net> wrote in message
> > > news:3fe373ce_1@news.arcor-ip.de...
> > >> Hi!
> > >> I need a i2c bus isolation with optocouplers or another technology.
> Google
> > >> doesn't know interesting hits. Any hints other than the Philips
> solution
> > >> with i2c bus drivers and optocouplers? An integrated solution as a
> cheap
> > >> sockable DIP or SMD device would be great.
> > >> I wonder that none of the big semiconductor producers is interested
> > >> producing such a device many people need. Hey marketing engineer, where
> > > are
> > >> you??
> > >> Greetings -
> > >> Henry
> >
> > > Did you just ask for isolation of Maxim/Dallas single-wire bus?
> >
> > > The basic problem is the same: the bus is essentially an open-drain
> > > bidirectional bus, but the available isolators are unidirectional. You
> need
> > > to bridge both the clock and the data line with two isloators each, one
> for
> > > each direction. To prvent inventing an isolating flip-flop, the isolator
> has
> > > to understand pretty deeply the bus protocol to select the direction
> > > properly. The contention mechanisms in I2C make this a challenging
> > > situation.
> >
> > Take look at http://www.esacademy.com/faq/i2c/q_and_a/faq/i2cqa3.htm.
> > This circuit should do the job (although I haven't tested it).
> >
> 
> Did you notice that there is a severe speed restriction?
> 
> The circuit does not go over 10 kHz, but the bus is 100 kHz or faster.

I don't see any obvious reason why this circuit won't work at higher
speeds than 10kHz.  But I do see a problem which would result in a
glitch when both sides are driving the bus and one side releases.  As
the released side rises, it has to reach a voltage of around 3.4 volts
before the opto cuts off enough to let the other side turn on to drive
back.  This will be a short glitch and it is likely that the side doing
the release will not be watching.  But if any transactions are edge
detected, this is likely to cause a false edge.  Perhaps this has
something to do with the speed limitation?  

-- 

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

"Jacek R. Radzikowski" <jacek+maqmba@spamer.die.die.die.piranet.org> wrote
in message news:bs4ltb$mki$1@www.itl.waw.pl...
> Tauno Voipio <tauno.voipio@iki.fi.spambait_remove.invalid> wrote:
>
> > "Henry" <otc_friend@gmx.net> wrote in message
> > news:3fe373ce_1@news.arcor-ip.de...
> >> Hi!
> >> I need a i2c bus isolation with optocouplers or another technology.
Google
> >> doesn't know interesting hits. Any hints other than the Philips
solution
> >> with i2c bus drivers and optocouplers? An integrated solution as a
cheap
> >> sockable DIP or SMD device would be great.
> >> I wonder that none of the big semiconductor producers is interested
> >> producing such a device many people need. Hey marketing engineer, where
> > are
> >> you??
> >> Greetings -
> >> Henry
>
> > Did you just ask for isolation of Maxim/Dallas single-wire bus?
>
> > The basic problem is the same: the bus is essentially an open-drain
> > bidirectional bus, but the available isolators are unidirectional. You
need
> > to bridge both the clock and the data line with two isloators each, one
for
> > each direction. To prvent inventing an isolating flip-flop, the isolator
has
> > to understand pretty deeply the bus protocol to select the direction
> > properly. The contention mechanisms in I2C make this a challenging
> > situation.
>
> Take look at http://www.esacademy.com/faq/i2c/q_and_a/faq/i2cqa3.htm.
> This circuit should do the job (although I haven't tested it).
>

Did you notice that there is a severe speed restriction?

The circuit does not go over 10 kHz, but the bus is 100 kHz or faster.

Tauno Voipio
tauno voipio @ iki fi

Tauno Voipio <tauno.voipio@iki.fi.spambait_remove.invalid> wrote:

> "Henry" <otc_friend@gmx.net> wrote in message
> news:3fe373ce_1@news.arcor-ip.de...
>> Hi!
>> I need a i2c bus isolation with optocouplers or another technology. Google
>> doesn't know interesting hits. Any hints other than the Philips solution
>> with i2c bus drivers and optocouplers? An integrated solution as a cheap
>> sockable DIP or SMD device would be great.
>> I wonder that none of the big semiconductor producers is interested
>> producing such a device many people need. Hey marketing engineer, where
> are
>> you??
>> Greetings -
>> Henry

> Did you just ask for isolation of Maxim/Dallas single-wire bus?

> The basic problem is the same: the bus is essentially an open-drain
> bidirectional bus, but the available isolators are unidirectional. You need
> to bridge both the clock and the data line with two isloators each, one for
> each direction. To prvent inventing an isolating flip-flop, the isolator has
> to understand pretty deeply the bus protocol to select the direction
> properly. The contention mechanisms in I2C make this a challenging
> situation.

Take look at http://www.esacademy.com/faq/i2c/q_and_a/faq/i2cqa3.htm.
This circuit should do the job (although I haven't tested it).

j.

rickman wrote:
> Tauno Voipio wrote:
> >
... snip ...
> >
> > The basic problem is the same: the bus is essentially an
> > open-drain bidirectional bus, but the available isolators are
> > unidirectional. You need to bridge both the clock and the data
> > line with two isloators each, one for each direction. To prvent
> > inventing an isolating flip-flop, the isolator has to
> > understand pretty deeply the bus protocol to select the
> > direction properly. The contention mechanisms in I2C make this
> > a challenging situation.
> 
> Depending on how the basic I2C controller is implemented, this is
> not a big deal.  If the I2C interface is totally within a chip,
> then it might be tricky.  But if the I2C interface is in a PLD or
> MCU where you can control the external interface, then it is a
> slam dunk.  All you need is access to the open drain driver (I am
> finally getting used to not calling it "open collector"...).  You
> substitute the OptoIsolator for the OD driver and add a second OI
> for the receive (on a separate MCU/PLD pin) and you are done!
> 
> The only electrical issue I see is that it would take a wopping
> pullup to supply a bunch of OI with current, so I expect you
> would need access to the bus Vcc (or is it Vdd?) and wire the OI
> inputs as pullups.  Then the active OI output would connect the
> bus to ground to draw current through the OIs.  This may require
> a lot more current than the bus is normally designed for.  But
> that should be a good thing since it will speed up the
> transitions (unless you are worried about the EMI).  Of course
> you could add a transistor driver to reduce the loading, but you
> still need a common Vcc to drive the bus side of the OI and
> transistor.

Simplify :-)  You want a one wire path that detects collisions,
can be 'wire or' connected, opto-isolated, etc.  Go back further
than open collectors and, presto: Current loop.  Think mark/space.

I have driven 20 mA current loops, opto-isolated, through
literally miles of extremely noisy environments, surrounded by
elevators, diathermy, x-rays, you name it.

-- 
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>  USE worldnet address!