The Well-Linuxed Car

[Roger Oberholtzer]

On Mon, 1 Dec 2003 10:42:47 -0500
"David A. Bandel" <david at pananix.com> wrote:

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> On Mon, 1 Dec 2003 15:15:30 +0100
> Roger Oberholtzer <roger at opq.se> wrote:
> 
> [snip]
> 
> > 
> > Even something as 'innocent' as an RS-232 port takes on new problems
> > in a vehicle if the equipment at both ends are not sharing the same
> > ground sense.
> 
> Boy have you hit a biggie on the head.  And since a vehicle doesn't have
> a true ground in the full sense of the term, you nailed it with "ground
> sense".  All equipment _must_ see the same ground from their point of
> view or you'll get all kinds of strange behavior and odd burnouts.  I
> see this problem on boats all the time. Aircraft share the same problem.

We have RS-232, parallel ports, Ethernet (both popular varieties) as well as
a few odd trigger connections. Oddly, we do not use RS-422, which is better
suited to this type of environment than is RS-232. History, I guess.

Incorrect/faulty grounding is the challenge in every new vehicle we build.
And remains an issue as the connectors age. We use military spec connectors,
but part of the 'spec' is regular maintenance. No connector lasts forever.

Some connectors are outside the vehicle, where road salt and oil becomes an
issue.


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