I2C in an automotive environment

[Amos K]

I'm starting a system design for my car that will need an interface
between each subsystem (alarm and locks, engine control, windows and
lights, stereo, displays ect...) I chose I2C over RS-485 because it is
widely accepted and easy to impliment with minimal parts. Has anyone
tried using it in an automotive environment? I'm concerned there might be
to much interference causing data transmittion problems.

Is there maybe a better thread for this question someone knows about?

Thanks for any input

-Amos

 

[Tomi Holger Engdahl]

Amos K <abk131@lycos.com> writes:

I'm starting a system design for my car that will need an interface
between each subsystem (alarm and locks, engine control, windows and
lights, stereo, displays ect...) I chose I2C over RS-485 because it
is widely accepted and easy to impliment with minimal parts.

I2C is widely accepted and eeasy to implement with minimal parts.
The traditional I2C is not useful outside the box for anything
that needs reliabity, because it is quite sensitive to interference
(unbalanced bus with open collector drivers and weak pull-up) and
the communication protocol/ICs does not have any useful built-in error
detection/correction.

I have heard somebody mention I2C over RS-485.
I have not heard much of it or seen it used anywhere, so I doubt
that it woudl be widely accepted.

Has anyone tried using it in an automotive environment?

I have not tried to use it in automotive enviroment.
I have used I2C on some other things...

I'm concerned
there might be to much interference causing data transmittion problems.

Is there maybe a better thread for this question someone knows about?

Thanks for any input

-Amos

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Amos K]

I was worried someone would say that. I've thought about using shielded
cable. Triax most likely, if I can find some. Think that would help
enough?

I've not heard of I2C over RS-485. I'll do some research but it seems to
me that it makes more sence to do straight 485. If I had a I2C sensor I
wanted to hook up it might be worth looking into. Then again it would
probably be easier and cheaper just to hook the sensor to a micro and put
that on the 485 drop.

Thanks for your input.



On 31 Dec 2003 13:21:57 +0200, Tomi Holger Engdahl
<then@solarflare.cs.hut.fi> wrote:

Amos K <abk131@lycos.com> writes:

I'm starting a system design for my car that will need an interface
between each subsystem (alarm and locks, engine control, windows and
lights, stereo, displays ect...) I chose I2C over RS-485 because it
is widely accepted and easy to impliment with minimal parts.

I2C is widely accepted and eeasy to implement with minimal parts.
The traditional I2C is not useful outside the box for anything
that needs reliabity, because it is quite sensitive to interference
(unbalanced bus with open collector drivers and weak pull-up) and
the communication protocol/ICs does not have any useful built-in error
detection/correction.

I have heard somebody mention I2C over RS-485.
I have not heard much of it or seen it used anywhere, so I doubt
that it woudl be widely accepted.

Has anyone tried using it in an automotive environment?

I have not tried to use it in automotive enviroment.
I have used I2C on some other things...

I'm concerned
there might be to much interference causing data transmittion problems.

Is there maybe a better thread for this question someone knows about?

Thanks for any input

-Amos

 

[Tomi Holger Engdahl]

Amos K <abk131@lycos.com> writes:

I was worried someone would say that. I've thought about using
shielded cable. Triax most likely, if I can find some. Think that
would help enough?

Can't sya for sure if triax would be gopod enough.
I2C in car environement sound very unrelible to me.

I've not heard of I2C over RS-485. I'll do some research but it seems
to me that it makes more sence to do straight 485.

Here are some lins for I2C-RS485 adapter plans I have found:

I2C - RS-485 adapter
http://vodka.tky.hut.fi/~jap/Electronics/I2C-adapter/

I2C Serial Port Adapter & Extender
http://zebra.tky.hut.fi/~jap/Electronics/I2C/SerialAdapter/

If I had a I2C
sensor I wanted to hook up it might be worth looking into. Then again
it would probably be easier and cheaper just to hook the sensor to a
micro and put that on the 485 drop.

Using I2C only on very short local communications between
the sensor and microcontrolelr, then the micrcontroller
communicates through RS-485 sounds the most sensible solution.
It coudl be a good idea to add some checksum etc. to the
communcation packets to make sure that data gets through
right and errors are detected when they occur.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/