Subject: Re: [its] novel use case for intra-vehicular wireless

From: Alison Chaiken <[email-masked]>
Date: Sun, 12 May 2013 13:32:35 -0700

I apologize for taking so long to answer these thoughtful messages: I have
simply been especially busy.

Rex Buddenberg offers:
Having spent ~40 years or so in the comms business one way or another, one
of the things I've learned is never to do with radio what you can do with
wireline.  There are lots of reasons, but a couple of the enduring ones are:
- capacity. . . .
- error rate. . . .

Rex, please note that the signals that Elo Touch Solutions suggested
sending over radio were button presses, or perhaps arrow keys on 4-segment
panels.    Data rate and error tolerance are hardly challenging in those
circumstances.

In these messages I have been trying to summarize what experienced
automotive designers tell me, and I have only been infrequently offering my
own opinion.   I was surprised, as I noted, to hear Elo advocate for
wireless in this application, as I indicated.

Rex added:
shift to UTP ethernet throughout.

Henry Ptasinski asks:
Why (and when) were they trying to use coax?  Too much electrical noise
from the engine?

Correct.  In fact, the first automotive transceivers for UTP are starting
to appear in cars just now via the Broadcom BroadR-Reach:

http://www.eetimes.com/design/automotive-design/4410090/Automotive-Ethernet--Evolution-in-the-fast-lane

Automotive environments are electrically noisy, with large temperature
swings and lots of vibration and dirt.   Most datacenter cabling solutions
are simply inapplicable.

Rex:
Is CAN a routable network?

CAN has no notion of an address, so no, to say the least, but that's a
whole other discussion and far too off-topic.    The industry wants to
deprecate CAN, but it's going to take a while.

Rex:
It's a usual habit in each of these industries to fix upon legacy end
systems and try to work from there. Legacy end systems tend to be  pretty
dumb

No one disagrees, but if we don't want to end up with extremely expensive
next-generation cars full of brand new microcontrollers with little field
testing, we need to be patient!

Henry:
Multiple displays will only be an improvement if the information is  well
organized and presented.

The multiple-display idea was presented by Mercedes and BMW at a
German-American Business Association panel discussion I attended about a
year ago.   Mercedes and BMW based the idea of disaggregation of large
console touch panels on data harvested from regular drivers who opted in to
a monitoring program.   They found that the drivers did not much use large
touch panels and continued to prefer hard buttons when they offered the
same function.   These companies suggested that four-segment buttons are
the most complex ones drivers can use without taking their eyes off the
road.     There is some notion that offering (for example)
up-down-right-left arrow panels in the top of one or more rotary mechanical
knobs is more usable than offering that functionality along with many
others on a large touchscreen.   Apparently currently shipping cars from
the German automakers are trying this approach.

Rex:
User interface?  What to do with LAN?

I am trying to enumerate how UI design may dictate what hosts appear on an
automotive intranet.

Michael Richardson asks:
It seems that you are agreeing with me that data cables are hard, but are
you also saying that a single power lead (assuming chassis ground) is also
hard?

I'm not saying that.    I work on automotive Linux kernel, not door-panel
design, so please take my comments about distributed power and signals in
that light!   I would like to encourage a dialog among the various
stakeholders so that best practices propagate into the automotive industry
but am unable to offer an informed opinion on many questions you might ask.

-- 
Alison Chaiken                           [email-masked]
650-279-5600                            http://{she-devel.com,
exerciseforthereader.org}
The intermediary between the head and the hands must be the heart.    --
Thea von Harbou