Searching \ for '[EE]: Isolated I2C' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/i2cs.htm?key=i2c
Search entire site for: 'Isolated I2C'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Isolated I2C'
2001\08\17@045924 by Alan B. Pearce

face picon face
I have a requirement to have an I2C link across an isolation boundary. The
voltage requirements of the boundary are not high, it is just that I am
needing to emulate some circuitry for testing purposes from the rest of the
test equipment.

I will not need to be running the I2C link at high speed, so I was thinking
in terms of opto-isolators to achieve this. Anyone have any experience in
this area, especially the bi-directional part?

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\08\17@060730 by Vasile Surducan

flavicon
face
I've played only with isolated 232 and other isolation devices in medical
equipment.
However for clk I think will work any photodiode-phototransistor
optocoupler like CNY17 or 4N series, depends on max frequency
requirements.
For data, I'll use two high frequency trigger schmitd inverter like MOC
5007 or H11L series, both have a two input nand gate which could be use
for enabling the sense of transmision ( receiving or transmiting ) and run
well up to 100kHz.
Vasile



On Fri, 17 Aug 2001, Alan B. Pearce wrote:

{Quote hidden}

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\08\17@083655 by Eisermann, Phil [Ridg/CO]

flavicon
face
       I did this a short while back. The device under test is powered by a
dropping capacitor, so isolation was required for the interface. It's not
quite the I2C protocol, but modified to reduce code size. It's a PIC12CE518.
The I2C on the measurement side (an 8051) ended up using three pins (clock,
tx, rx). The PIC device under test uses two pins with pullup resistors. Same
principle as I2C, though. I used three (3) 4N36 with the base grounded
through a resistor to increase turn-off times of the phototransistor. The
base resistor is a compromise between speed and current. So you might play
with that for your circuit. One for the clock, one for tx, one for rx. I
also ended up using a small NPN to interface to the circuit under test,
which has very low drive capability. The whole thing is powered by an audio
transformer driven like a half-bridge converter to provide the power for the
optos. No feedback to keep it simple. Since the PIC is powered by an Xcap,
it really has very limited drive, so this was necessary.

I can take a quick rise/fall time measurement of my configuration if you are
interested. Feel free to ask for more details.


> {Original Message removed}

2001\08\17@104504 by Chris Carr

flavicon
face
No problem. We use OptoIsolators. Do you want just the Clock and Data Lines
or Clock, Data and Interrupt. ?

Regards

Chris Carr

> I have a requirement to have an I2C link across an isolation boundary. The
> voltage requirements of the boundary are not high, it is just that I am
> needing to emulate some circuitry for testing purposes from the rest of
the
> test equipment.
>
> I will not need to be running the I2C link at high speed, so I was
thinking
> in terms of opto-isolators to achieve this. Anyone have any experience in
> this area, especially the bi-directional part?
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
>
>

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\08\17@110012 by Alan B. Pearce

face picon face
>No problem. We use OptoIsolators. Do you want just the Clock and Data Lines
>or Clock, Data and Interrupt. ?

Just clock and data is what I am after.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\08\17@110913 by Chris Carr

flavicon
face
Give me a couple of hours and I will post a circuit. I have to do a couple
of urgent jobs first.

Regards

Chris Carr



{Original Message removed}

2001\08\17@111541 by Alan B. Pearce

face picon face
>Give me a couple of hours and I will post a circuit. I have to do a couple
>of urgent jobs first.

Appreciate that. It is not urgent (I will not be looking at it till Monday
anyway), so do not bust a gut over it.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\08\18@173331 by Chris Carr

flavicon
face
> >Give me a couple of hours and I will post a circuit. I have to do a
couple
> >of urgent jobs first.
>
> Appreciate that. It is not urgent (I will not be looking at it till Monday
> anyway), so do not bust a gut over it.
>
You mean you are not working 12+ hours a day, 265 days a year. I must be
doing something wrong, it cannot be just age related.

The scanner has decided to throw a wobbly and the Digital Camera is in
Scotland being "evaluated" by one of my Nephews, so I will attempt to
describe the circuit.

Two Identical circuits are require for SDA and SCK. I will describe SDA.

Each Circuit requires
2 off BAT85 or similar (OA47 ?) low volts drop is important, call them D1
and D2.
2 0ff 6N139 optocoupler with Darlington Output. Call them OC1 and OC2

Assume we have two Isolated Circuits called Left Hand (LH) and Right Hand
(RH)

The Collector of the first transistor of OC1 (Pin 8) is connected to RH
+5volt
OC2 Pin 8 is connected to LH +5v

The Emitter of OC1 (Pin 5) is connected to RH 0v (Earth)
OC2 Pin 5 is connected to LH 0v

The Collector of the Second Transistor of OC1 (pin 6) is connected to a 3k9
resistor, the other side of which is connected to RH +5volt
OC2 pin6 is connected to a 3k9 resistor the other lead of which is connected
to LH 5v.

The Cathode of D1 is connected to the Anode of the Photodiode of OC1 (pin 2)
D2 Cathode is connected to OC2 pin 2

The Anode of D1 is connected to the Cathode of the Photodiode of OC1 (pin 3)
The Anode of D2 is connected to OC2 pin 3

The Anode of D1 is connected to LH SDA
The Anode of D2 is connected to RH SDA

The Cathode of D1 is connected to OC2 Second Collector (pin 6)
The Cathode of D2 is connected to OC1 pin 6

The assumption is made that the mandatory 3k3 pull-up resistor is present on
both LH and RH SDA Lines.

Circuit Operation. A low on LH SDA causes LED OC1 to light (path through the
3k9 resistor). This results in the second transistor of the OC1 Darlington
Pair to turn on taking the RH SDA low through D2 (current through the 3k3
pull-up resistor).

If my description is inadequate Alan, Email me off-list with your Fax number
and I'll send you a copy of my sketch which is currently on the back of the
Marlborough Pack.  8-)

Regards

Chris Carr

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email spam_OUTlistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body


2001\08\18@194351 by Mick Kent

flavicon
face
100 days a year off; you must be a school teacher!
----- Original Message -----
From: "Chris Carr" <.....nyedKILLspamspam@spam@BTINTERNET.COM>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Saturday, August 18, 2001 4:32 PM
Subject: Re: [EE]: Isolated I2C


> > >Give me a couple of hours and I will post a circuit. I have to do a
> couple
> > >of urgent jobs first.
> >
> > Appreciate that. It is not urgent (I will not be looking at it till
Monday
{Quote hidden}

3k9
> resistor, the other side of which is connected to RH +5volt
> OC2 pin6 is connected to a 3k9 resistor the other lead of which is
connected
> to LH 5v.
>
> The Cathode of D1 is connected to the Anode of the Photodiode of OC1 (pin
2)
> D2 Cathode is connected to OC2 pin 2
>
> The Anode of D1 is connected to the Cathode of the Photodiode of OC1 (pin
3)
> The Anode of D2 is connected to OC2 pin 3
>
> The Anode of D1 is connected to LH SDA
> The Anode of D2 is connected to RH SDA
>
> The Cathode of D1 is connected to OC2 Second Collector (pin 6)
> The Cathode of D2 is connected to OC1 pin 6
>
> The assumption is made that the mandatory 3k3 pull-up resistor is present
on
> both LH and RH SDA Lines.
>
> Circuit Operation. A low on LH SDA causes LED OC1 to light (path through
the
> 3k9 resistor). This results in the second transistor of the OC1 Darlington
> Pair to turn on taking the RH SDA low through D2 (current through the 3k3
> pull-up resistor).
>
> If my description is inadequate Alan, Email me off-list with your Fax
number
> and I'll send you a copy of my sketch which is currently on the back of
the
{Quote hidden}

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email EraseMElistservspam_OUTspamTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body


2001\08\19@014822 by Chris Carr

flavicon
face
Mick Kent wrote :
> 100 days a year off; you must be a school teacher!

Finger problems, It should have read 12+ hours 365 days a year.
I live in hope of being able to afford one day off every 4 years   8-)

Chris Carr
{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamspam_OUTmitvma.mit.edu


2001\08\20@044534 by Alan B. Pearce

face picon face
>Mick Kent wrote :
>> 100 days a year off; you must be a school teacher!

>Finger problems, It should have read 12+ hours 365 days a year.
>I live in hope of being able to afford one day off every 4 years   8-)

>>> You mean you are not working 12+ hours a day, 265 days a year. I must be
>>> doing something wrong, it cannot be just age related.


I don't get paid enough to do that - I'm only a lowly civil servant who is
worse off than the nurses, police firemen...... etc.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2001\08\24@091424 by Alan B. Pearce

face picon face
I have worked through your description Chris, and can make sense of it. What
I drew out makes sense with your operation description as well.

It is now going to take me a little while to get the parts together, PCB
done, and assembled as it is one of the slightly lower priorities in an
extremely tight project.

Many thanks for the description.

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestKILLspamspammitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...