[rescue] Slightly OT: ?Bad Cap Saga
jorge234q at yahoo.com
Wed Aug 20 13:08:44 CDT 2008
--- On Wed, 8/20/08, Geoffrey S. Mendelson <gsm at mendelson.com> wrote:
> >Even if that's true of most of them (I'm not competent to comment on
> >that), how does that justify cutting off the rest?
> Becuase in a world where people buy according to price from
> the wholesaler, to the retailer, to the customer, any extra
> feature adds more money to the final price.
Exactly. This is one of the zero-th order criteria you can
use to identify the "newbie engineers" in a company -- they
want to add all sorts of "options" to a design to cover all
sorts of *potential* uses.
Even after many years of designing systems, I found myself
wanting to squeeze a few little hooks in to deal with
spin-off products ("Model 2", etc.) without having to
redesign a new product. :<
Eventually, I've grown to realize that it's best to design
*the* product that you need and, if you need a *different*
product, design *that* product separately.
Of course, this is much more practical nowadays since I
can just take the artwork for a board and move the tracks
around on a screen instead of having to lift black tape,
> >Note that a lot of single-board computers have parallel ports, just not
> >labeled as such (they're typically called something like "GPIO pins");
> >clearly I'm not the only person who wants them.
> Single board computers are usually put INTO things, and not computers.
> The market is quite different. So much different in fact that many
> microprocessor chips for embedded use have GPIO ports on them.
... because, in those embedded applications, you almost *always* need
discrete signals to tie to various odds and ends. E.g., to control
a FET that powers up a subsystem; or, to illuminate an indicator;
For *diagnostic* purposes, I usually reserve a spot in the address
space where I can *hang* some logic onto a production board (via
an ICE clip, etc.) so that the system behaves AS IF that hardware
was part of the original design yet doesn't burden the manufactured
product with the cost of these diagnostic/manufacturing aids.
And, the cost of laying out a little "add on" board like this is
peanuts in The Grand Scheme of Things (< $1K). Very handy as it
lets you put lots of stubs in your code AND LEAVE THEM THERE
(this is important in some industries where you can't change the
codebase) so that you can get this diagnostic information without
having to do anything special to the existing product (e.g.,
including devices in the field)
More information about the rescue