[conspire] Warning: You'll never get your time back from this thread

[Rick Moen]

The best-equipped and most reliable local retail vendor for computer
parts and supplies, is Central Computer, with six Bay Area stores plus
one in China.

Or is it Central Computers?  Or is it Central Computer System?


For long years living in San Francisco, Concord, San Francisco again,
San Mateo, San Francisco again, and finally Menlo Park, various Central
Computer retail locations have always been my go-to.  Fry's, you say?
Don't make me laugh.  You trudge through the warehouse-style experience
that is Fry's Electronics, but find that their apparently large
selection is mostly junk, and so their selection of what you would
_want_ is small.  Nice weekly specials, if you happen to want what
they're stocking up this week.  

But, hey, a few years back, I looked for their Web site, and it's
https://www.centralcomputers.com/ .  Header image in large block sans
serif letters says 'CENTRAL COMPUTERS'.

So, I had to wonder, had I gotten it subtly wrong all these years?  
Is this the first sign of dementia, and next I'll be calling my wife
from Watsonville saying I have no idea how I got there?

Store Hours and Locations page has photos of their storefronts, showing
the firm's name in big letters:

Pleasanton:  Central Computers
Sunnyvale:  Central Computers
Santa Clara (HQ):  Central Computer
San Francisco:  Central Computer
Newark:  Central Computers
San Mateo:  Central Computers
Shenzen City:  Central Computers

Copyright notice in the page footer says Central Computers.  Company
profile page says 'Central Computers, Inc.'  Careers / Employment page
says the name of the firm is 'Central Computer System'.   Employment
application form says 'Central Computers, Inc.'  Twitter handle is
@centralcomputer with an associated identifier string of 'Central
Computers'.

Best guess:  This is the Hamlet of computer retailers:  They've never
made up their mind.


Locally in Menlo Park, see also the small but excellent food market 
at Willow Road and Middlefield -- the one that stocks 1,000 microbrews
-- which has a side on one side saying 'Willow Market' and one on the
other side saying 'Willows Market'.


Here, let me to try to save you from this thread being a -total- loss of
your time:

I have two eBook readers, a small Kindle DO110 (4th Gen) that is pretty
much a dedicated book device, and a much larger Nook Tablet BNTV250.
The Kindle was nearly out of power, so I looked around for the crummy
USB cable we bought for it while traveling - and temporarily couldn't
find it.  (It later turned up, exactly where I left it so I could find
it easily.)

One end of the temporarily missing cable is the USB A-Type male that
everyone knows because it's what plugs into your computer ports.  See:
http://www.cablestogo.com/learning/connector-guides/usb  The other is
Micro-USB B male, the one with slanted sides.  (Again, see page, which
make these and other variations of physical connectors clear.)


I rummaged in my knapsack (not to be confused with napping in your
rucksack). I found four other apparently just-like-that cables, and
borrowed one from Deirdre.

Surely all cables with USB A-Type male at one end and Micro-USB B male 
at the other are functionally interchangeable, right?  The universe
cannot be that perverse, can it?  (Ah, you're way ahead of me.  Of
course it can.)

o  Two were identifiable as the charging cables that came with my
   Revolights kit (http://revolights.com/) for my bicycle.  There's a
   Li-Ion battery for each wheel hub.  To charge them, you detach them 
   and use the provided USB cable from a computer or something to 
   provide +5V DC charging power.

o  One was actually a USB A-Type male cabled to a USB Mini-b (5-pin)
   male -- again, see page illustration -- plugged into an adapter.
   The adapter was USB Mini-b (5-pin) female on one side and Micro-USB 
   B male on the other.

o  One turned out _not_ to be the right sort.  It was USB A-Type male 
   on one end and a proprietary Samsung cellular telephone male 
   connector on the other -- left over from a discarded mobile phone.
   It got put aside and will be donated to Goodwill Industries or 
   someone.

o  The one borrowed from Deirdre, USB A-Type male to Micro-USB B male.


With each of these in turn, I connected my Kindle to my laptop.
Charging power started arriving at the Kindle, but the laptop OS 
could not mount it (as normal and necessary for putting books on and
off).

I had to wonder:  Is the Kindle defective?  Is the laptop OS USB
service wonky?  I USB-connected my backup hard drive to the laptop.
To my relief, it mounted.  OK, computer's fine.  I borrowed Deirdre's
known-good and essentially identical mini-Kindle:  None of the four 
candidate cables could mount it.

So, I thought, broken Kindle, or four broken cables?

Then, I realised, wait, people often use USB cables for non-data 
purposes, most notably charging devices needing +5V DC, and so it's
_very_ likely cables for that purpose don't bother to connect all the
pins, just the ones for power.  The Revolights cables were case in
point, and I looked at them closely:  Not only were the connectors
exactly what are used for data, but each end also bears the familiar
USB-indicating forking-path logo (see diagrams).  The cable thickness
also was wide enough to carry all signals, but my best guess is they
don't.

So, my takeaway is that you _cannot_ determine what alleged USB cables
can actually do USB just by looking at them.  So, it's an extremely
good idea to label such cables as soon as possible, while you still 
remember what they came with and what they're for.

Which I've now done.

The missing crummy cable turned up -- stuffed conveniently into my
laptop bag.  I used it with the Kindle, which duly mounted -- so the
Kindle is back to known-good.  I call the cable 'crummy' because
somewhere in the flat-ribbon cable is a developing wire break, such that
connected devices unmount if you jostle the cable.  

I have a replacement cable on order from mail order.

The USB A-Type male to USB Mini-b (5-pin) male cable joined to an
adapter to Micro-USB B male turns out to be mystery.  I cannot determine
exactly why the Kindle doesn't mount.  Maybe the cable is power-only,
not data.  Maybe the adapter is.  Maybe both.  I'd love to see if the 
cable can be used to mount a Mini-USB block device.

I don't have a Mini-USB-connectable _block_ device, but my Motorola
RAZRv3 flip-phone has that kind of jack.  Mini-USB was essentially a
mid-2000s connector, so that fits, as it's a 2005-2007 mobile.

I should explain:  USB is less a connection type than it is a cabling 
and electrical standard over which all sorts of crazy protocols can be
layered.  One of those crazy protocols is MTP, Media Transfer Protocol, 
which is essentially serial communication with some file metadata
headers, and ability to send commands such as 'Please delete the
following named remote file'.  So, this is tantamount to talking to your
mobile over a modem line.  (Very similar is PTP, Picture Transfer Protocol.)

My antique Motorola's RAZRv3 is problematic to talk to over your choice
of PTP-flavour USB or Bluetooth; this was covered in some detail in a
2006 Linux Gazette discussion in which I participated
(http://linuxgazette.net/134/misc/lg/talkback_133_tag_html.html).  I've
succeeded in the recent past over USB, to take photos off and to 
change the ring tone to Stephen Colbert saying 'Your phone is ringing!
Your phone is ringing!' -- but haven't succeeded lately.  This problem
will doubtless get resolved via a replacement mobile from the current
decade.  Meanwhile, I don't know what if anything ails that cable (let
along the associated adapter to Micro-USB B male), and have marked it
accordingly.


Separate from the foregoing mess is the Nook Tablet.  This is a heavy,
full-size tablet computer, colour screen, came with its own charger 
with a long cable.  I rummaged and refound that charger + long cable
because I'm belatedly reflashing it to have Android 5.1 'Lollipop'
based on CyanogenMod, rather than the very limited Barnes and Noble 
preload.
https://www.perfectlyandroid.com/shop/android-lollipop-for-nook-tablet/

I hadn't used the Nook Tablet in dog years, as I intended to do
CyanogenMod conversion before loading it up, and hadn't gotten to it.
(Actually, I bought it used and pretty much immediately set aside
pending a new OS.)  So, I had to rummage for its charger + cable.  The
cable has what looks like the now-familiar Micro-USB B male plug -- the
one with the slanted sides.  

I wondered for a while:  Have I misplaced the cable needed to connect
the Nook to a computer for data transfer?  Then I looked closer at the
charger + cable -- and remembered that they are two separate things
plugged together.  The charger is the AC to +5V DC dongle, and has,
guess what?  Right, a bog-standard USB A-Type female jack like the ones
computers have.  The cable has a USB A-Type male plug on one (that) end,
and the other is the Micro-USB B male plug.  But is it really Micro-USB
B?  By this point, I'd become more than wary.

No, it's not.  https://bookclubs.barnesandnoble.com/thread/7740
(Page talks about Nook Color, but also applies also to the similar Nook
Tablet.)

  There are lots of discussions concerning the special charging
  micro-USB connector and cable for the Nook Color.
 
  Here's the deal - the normal USB port or charger produces 5v @ 500ma.
  The Nook Color AC adapter can produce 5v @ 1.9A (1900ma).  Actually, 
  any charger will work ok, it just takes longer to charge the battery...  
  the more "amps" the faster the charging rate; bigger bucket filling 
  the bathtub.
 
  To handle the extra current flowing to the Nook Color, the special
  micro-USB connector is "longer" and has an extra 12 pins at the tip,
  that go deeper into the special micro-USB connector on the Nook Color.
 
  A normal micro-USB cable can still be used for data transfers or
  slow/trickle charging,  since it will only go in the normal depth and
  not make contact with the deeper special pins.
  
So, the Nook cable has what looks like a normal 5-pin Micro-USB B male
plug, but it's not one, but rather a bespoke 12-pin one and cannot work
with anything else -- but regular 5-pin Micro-USB B plugs can work with
the Nook, just not charging it as quickly.  

tl;dr:  Your label-making machine is your friend.  Use it to label your
USB cables while you still know what they are and can do.  I just did.


Coming soon to devices near you:  USB C-Type, the newest USB connector
do-it-all flavour of the month (introduced 2014).  Again, see picture
and description at
http://www.cablestogo.com/learning/connector-guides/usb .  Plug has a
rounded oval outline, and there are 24 pins, and it's reversible.
(I.e., you cannot attempt to mash it in upside-down, as either way up
works the same.)  All the other Mini and Micro variants are now being
called 'legacy'.  Moreover, Intel, one of the seven companies behind USB
standards, is pushing hard for USB C-Type to finally replace all
headphone and other audio jacks on data devices.  And it might happen.