May
1999, Issue 106
Dallas
1-Wire Devices, (Part 2):
All
on One
by
Jeff Bachiochi
If
you’re looking for a needle in a haystack, maybe
you could use a Dallas 1-wire device. Well, maybe
not, but Jeff shows how its unique addressing systems
enable multiple devices to run off one I/O pin.
We
didn’t have to be in Boston until Saturday evening,
but Kristafer (my youngest) and I left home Friday to
spend the night in Waltham where my oldest son lives.
That
gave the three of us a whole day to bum around Boston
before Kris and I were scheduled to meet the rest of
the Cub Scouts at the Boston Museum of Science for a
special camp-out, er, camp-in.
Getting
around Boston isn’t too tough. The Mass Transit
Authority (MTA) offers multiple subway routes into and
out of the city. The four main lines converge at a hub
of four midtown stops where you can switch between the
red, blue, orange, and green lines.
We
spent a lot of time looking at the MTA maps, and Kris
had the task of determining our route between destinations.
He quickly learned the importance of knowing which direction
to head and where to switch lines. All of this got me
thinking about networking and the importance of addressing.
Before
you could say "Paul Revere," it was time for
us to head over to the museum. Just imagine hundreds
of Cub Scouts funneling into the museum, all carrying
armfuls of sleeping paraphernalia! Not a pretty sight,
but well choreographed on the part of the museum. Apparently,
these sleep-ins are a common occurrence.
You
might think that coordinating so many kids would be
a nightmare, but we were quickly split into small groups
and whisked away to our own little corner of the facility.
Scheduled events kept us busy until midnight. When they
say, "lights out at midnight," that’s
what they mean. Everything goes off; the lights, the
exhibits. It’s eerie, camping under a black sky
with no stars.
As
I drifted off to sleep thinking about the number of
people staying here, I wondered how they would ever
be able to find anyone. Just then a small light appeared
and a voice asked, "Is there a Josh Nixon here?
I found a bottle of medication with your name on it."
Josh piped up that he was indeed here, but what
intrigued me was how we were located so easily.
It
seems that at registration each visitor was given an
identification slot. The schedule for the whole weekend
was preprogrammed into a computer to identify where
each visitor would be (or at least should be) during
that time. With the comforting notion that big brother
was watching over us, I fell fast asleep dreaming of
buses driving around with large hexadecimal addresses
painted on them.
