USB chargers, anyone ?

A

Arfa Daily

Guest
Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

I'm not particularly concerned at this, because I am only interested in the
5 volts, so cut the other two wires off. There is one thing that slightly
concerns me, though. A couple of months back, I had a similar need, and
purchased one of the slightly larger ones that you see on eBay - like a
small wall-wart. It went into service powering an ethernet wireless bridge
dongle to allow my sat box to connect to the network. It's not a feature
that I use often, so I hadn't noticed that it was no longer working, and you
can't easily see the supply, as it is plugged into an extender block fixed
to the back of the TV. When I came to plug in my new supply to the same
extension block, I noticed that the other one looked 'skewed' in the socket,
and the LED wasn't on. When I pulled it out, it was obvious that it had
'exploded' internally, blowing the lid half off. When I took it apart, it
had indeed had a major failure, with a big silvery blast mark where the line
power came in via a small resistor.

When I looked at the USB connector on the bottom of this one, pins 1 and 4
were the 5v output and gnd, but pins 2 and 3 were joined together, and had a
couple of resistors hooked to them, and disappearing into the circuitry. So
why is this ? Do they perhaps make 'alternate' use of these pins for
flagging when charging is complete or something ? Even if they did, I can't
see that it would be an issue to have the supply running continuously. I
have a similar one for my iPod that I leave plugged in all the time, and 90%
of the time, it's just a dangling USB lead so no load at all.

Was I just unlucky that a crappily built Chinese switcher failed on me in
just a couple of months, or did it get upset because it was not being used
for its intended purpose, leaving pins 2 and 3 always open ? I just don't
want the same thing happening again to my new one ...

Arfa
 
Does everyone out there think Wikipedia is a pile of lies and useless
twaddle?

http://en.wikipedia.org/wiki/Usb

Scroll down to the Physical Appearance section.

VBUS is supposed to be loaded with no more than 0.5 amperes (0.9 for USB
3.0). What happens if you try to pull more than that (presumably) depends on
the design of the power supply feeding pins 1 and 4.
 
Perhaps I should have read a bit further. This is probably what you're
looking for...

Charging ports and accessory charging adapters
The USB Battery Charging Specification of 2007 defines new types of USB
ports, e.g., charging ports.[44] As compared to standard downstream ports,
where a portable device can only draw more than 100 mA current after digital
negotiation with the host or hub, charging ports can supply currents above
0.5 A without digital negotiation. A charging port supplies up to 500 mA at
5 V, up to the rated current at 3.6 V or more, and drop its output voltage
if the portable device attempts to draw more than the rated current. The
charger port may shut down if the load is too high.

Charging ports exist in two flavors: charging downstream ports (CDP),
supporting data transfers as well, and dedicated charging ports (DCP),
without data support. A portable device can recognize the type of USB port
from the way the D+ and D- pins are connected. For example, on a dedicated
charging port, the D+ and D- pins are shorted. With charging downstream
ports, current passing through the thin ground wire may interfere with
high-speed data signals. Therefore, current draw may not exceed 900 mA
during high-speed data transfer. A dedicated charge port may have a rated
current between 0.5 and 1.5 A. There is no upper limit for the rated current
of a charging downstream port, as long as the connector can handle the
current (standard USB 2.0 A-connectors are rated at 1.5 A).

Before the battery charging specification was defined, there was no
standardized way for the portable device to inquire how much current was
available. For example, Apple's iPod and iPhone chargers indicate the
available current by voltages on the D- and D+ lines. When D+ = D- = 2V, the
device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device may
pull up to 1000 mA of current.[45]

Dedicated charging ports can be found on USB power adapters that convert
utility power or another power source - e.g., a car's electrical system - to
run attached devices and battery packs. On a host (such as a laptop
computer) with both standard and charging USB ports, the charging ports
should be labeled as such.[44]

To support simultaneous charge and sync, even if the communication port
doesn't support charging a demanding device, so called accessory charging
adapters are introduced, where a charging port and a communication port can
be combined into a single port.

The Battery Charging Specification 1.2 of 2010 [12] makes clear, that there
are safety limits to the rated current at 5 A coming from USB 2.0. On the
other hand several changes are made and limits are increasing including
allowing 1.5 A on charging ports for unconfigured devices, allowing high
speed communication while having a current up to 1.5 A and allowing a
maximum current of 5 A.
 
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?
Click to expand...
AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.

--
Rich Webb Norfolk, VA
 
Arfa Daily wrote:
Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

I'm not particularly concerned at this, because I am only interested in the
5 volts, so cut the other two wires off. There is one thing that slightly
concerns me, though. A couple of months back, I had a similar need, and
purchased one of the slightly larger ones that you see on eBay - like a
small wall-wart. It went into service powering an ethernet wireless bridge
dongle to allow my sat box to connect to the network. It's not a feature
that I use often, so I hadn't noticed that it was no longer working, and you
can't easily see the supply, as it is plugged into an extender block fixed
to the back of the TV. When I came to plug in my new supply to the same
extension block, I noticed that the other one looked 'skewed' in the socket,
and the LED wasn't on. When I pulled it out, it was obvious that it had
'exploded' internally, blowing the lid half off. When I took it apart, it
had indeed had a major failure, with a big silvery blast mark where the line
power came in via a small resistor.

When I looked at the USB connector on the bottom of this one, pins 1 and 4
were the 5v output and gnd, but pins 2 and 3 were joined together, and had a
couple of resistors hooked to them, and disappearing into the circuitry. So
why is this ? Do they perhaps make 'alternate' use of these pins for
flagging when charging is complete or something ? Even if they did, I can't
see that it would be an issue to have the supply running continuously. I
have a similar one for my iPod that I leave plugged in all the time, and 90%
of the time, it's just a dangling USB lead so no load at all.

Was I just unlucky that a crappily built Chinese switcher failed on me in
just a couple of months, or did it get upset because it was not being used
for its intended purpose, leaving pins 2 and 3 always open ? I just don't
want the same thing happening again to my new one ...
Click to expand...

Check out this page for the resistors that are needed to turn on most
USB sources.

http://www.beyondlogic.org/usbnutshell/usb2.shtml
 
Cydrome Leader wrote:
Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.

Isn't it sad all this garbage is needed to send 5 volts down a cable?
Click to expand...

Needing three resistors is sad?
 
Isn't it sad all this garbage is needed to send 5 volts down a cable?
Click to expand...
I've seen the USB 2.0 specs, and they're beyond unbelievable. You'd think
what appears to be a simple interface would take only ten pages or so to
define, but it takes 10 or 20 times that.

USB might be "over-defined", but at least it works. I can't think of a USB
product I've owned that didn't work correctly. From my point of view, this
is not an accident. Somebody did a lot of thinking to make sure there
weren't any "gotchas" in the system specification.
 
Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.
Click to expand...
Isn't it sad all this garbage is needed to send 5 volts down a cable?
 
Cydrome Leader wrote:
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

Cydrome Leader wrote:

Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.

Isn't it sad all this garbage is needed to send 5 volts down a cable?


Needing three resistors is sad?

yeah, it is.

USB is not like ethernet where adding power happened later on and there is
a chance to do weird stuff like plug two PoE switches into each other
with a patch cable. USB doesn't support "illegal" scenarios like this due
to the connectors, so any extra signalling is just bullshit to lockout
devices or make you get stuff you should not need.
Click to expand...

A couple cents worth of resistors to turn on the port is a simple and
sensible way to protect the port. It was designed that way, not added
at a later date. Look at the data sheets for some of the hub ICs.
 
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
Cydrome Leader wrote:

Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.

Isn't it sad all this garbage is needed to send 5 volts down a cable?


Needing three resistors is sad?
Click to expand...
yeah, it is.

USB is not like ethernet where adding power happened later on and there is
a chance to do weird stuff like plug two PoE switches into each other
with a patch cable. USB doesn't support "illegal" scenarios like this due
to the connectors, so any extra signalling is just bullshit to lockout
devices or make you get stuff you should not need.
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:k2qia0$jbf$1@dont-email.me...
Perhaps I should have read a bit further. This is probably what you're
looking for...

Charging ports and accessory charging adapters
The USB Battery Charging Specification of 2007 defines new types of USB
ports, e.g., charging ports.[44] As compared to standard downstream ports,
where a portable device can only draw more than 100 mA current after
digital
negotiation with the host or hub, charging ports can supply currents above
0.5 A without digital negotiation. A charging port supplies up to 500 mA
at
5 V, up to the rated current at 3.6 V or more, and drop its output voltage
if the portable device attempts to draw more than the rated current. The
charger port may shut down if the load is too high.

Charging ports exist in two flavors: charging downstream ports (CDP),
supporting data transfers as well, and dedicated charging ports (DCP),
without data support. A portable device can recognize the type of USB port
from the way the D+ and D- pins are connected. For example, on a dedicated
charging port, the D+ and D- pins are shorted. With charging downstream
ports, current passing through the thin ground wire may interfere with
high-speed data signals. Therefore, current draw may not exceed 900 mA
during high-speed data transfer. A dedicated charge port may have a rated
current between 0.5 and 1.5 A. There is no upper limit for the rated
current
of a charging downstream port, as long as the connector can handle the
current (standard USB 2.0 A-connectors are rated at 1.5 A).

Before the battery charging specification was defined, there was no
standardized way for the portable device to inquire how much current was
available. For example, Apple's iPod and iPhone chargers indicate the
available current by voltages on the D- and D+ lines. When D+ = D- = 2V,
the
device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device
may
pull up to 1000 mA of current.[45]

Dedicated charging ports can be found on USB power adapters that convert
utility power or another power source - e.g., a car's electrical system -
to
run attached devices and battery packs. On a host (such as a laptop
computer) with both standard and charging USB ports, the charging ports
should be labeled as such.[44]

To support simultaneous charge and sync, even if the communication port
doesn't support charging a demanding device, so called accessory charging
adapters are introduced, where a charging port and a communication port
can
be combined into a single port.

The Battery Charging Specification 1.2 of 2010 [12] makes clear, that
there
are safety limits to the rated current at 5 A coming from USB 2.0. On the
other hand several changes are made and limits are increasing including
allowing 1.5 A on charging ports for unconfigured devices, allowing high
speed communication while having a current up to 1.5 A and allowing a
maximum current of 5 A.
Click to expand...
Thanks for that William

On the face of it, then, it would seem that a voltage on the data pins is
used to inform the USB device how much current it can take, which in the
case of the 'port' being on a 1 amp charger, would be the full spec whack of
1000mA. Since posting this, I had a closer look at the blown PSU, and the
two resistors form a potential divider across the 5v rail, so that would tie
in nicely. At least I know now that the extra wires are for the benefit of
the device hanging on the charger, and not to inform the charger about
anything, so I guess that confirms that I was just unlucky with the supply
that blew.

Arfa
 
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:RuSdnSCr0J7iRc3NnZ2dnUVZ_vCdnZ2d@earthlink.com...
Arfa Daily wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the
USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where
it's
all built into a standard sized UK 13A mains wall plug. It came with a
USB
to Apple lead, so I cut the Apple connector off, fully expecting there to
be
only two wires - Gnd and +5v - in the cable, but there was actually 4
thin
wires. So I then assumed that they had maybe just doubled up on the
wires,
as this thing is rated at 1 amp output. But again, no. All four wires
were
separate, so I checked what was coming out of it. Just over 5v between
black
and red, so that's ok, but measuring between black and green, and black
and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could
they
be just 'pullup' values to keep the "data +" and "data -" lines quiet
when
it has a genuine USB device connected to it ?

I'm not particularly concerned at this, because I am only interested in
the
5 volts, so cut the other two wires off. There is one thing that slightly
concerns me, though. A couple of months back, I had a similar need, and
purchased one of the slightly larger ones that you see on eBay - like a
small wall-wart. It went into service powering an ethernet wireless
bridge
dongle to allow my sat box to connect to the network. It's not a feature
that I use often, so I hadn't noticed that it was no longer working, and
you
can't easily see the supply, as it is plugged into an extender block
fixed
to the back of the TV. When I came to plug in my new supply to the same
extension block, I noticed that the other one looked 'skewed' in the
socket,
and the LED wasn't on. When I pulled it out, it was obvious that it had
'exploded' internally, blowing the lid half off. When I took it apart, it
had indeed had a major failure, with a big silvery blast mark where the
line
power came in via a small resistor.

When I looked at the USB connector on the bottom of this one, pins 1 and
4
were the 5v output and gnd, but pins 2 and 3 were joined together, and
had a
couple of resistors hooked to them, and disappearing into the circuitry.
So
why is this ? Do they perhaps make 'alternate' use of these pins for
flagging when charging is complete or something ? Even if they did, I
can't
see that it would be an issue to have the supply running continuously. I
have a similar one for my iPod that I leave plugged in all the time, and
90%
of the time, it's just a dangling USB lead so no load at all.

Was I just unlucky that a crappily built Chinese switcher failed on me in
just a couple of months, or did it get upset because it was not being
used
for its intended purpose, leaving pins 2 and 3 always open ? I just don't
want the same thing happening again to my new one ...


Check out this page for the resistors that are needed to turn on most
USB sources.

http://www.beyondlogic.org/usbnutshell/usb2.shtml
Click to expand...
Cheers

Arfa
 
There is a typo on that document that I don't have the time to find the
correct info for. This (1st paragraph, second last sentence) doesn't
make sense:

"A charging port supplies up to 500 mA at 5 V, up to the rated current
at 3.6 V or more,..."

Couldn't find a ready explanation for the rated current, but 3.6A may be
what the author meant, however I see later where the rated current is
more like 1.5A with 5A maximum.

Someone with more time can find the correct reference and fix that
article...

John :-#)#

William Sommerwerck wrote:
Perhaps I should have read a bit further. This is probably what you're
looking for...

Charging ports and accessory charging adapters
The USB Battery Charging Specification of 2007 defines new types of USB
ports, e.g., charging ports.[44] As compared to standard downstream ports,
where a portable device can only draw more than 100 mA current after digital
negotiation with the host or hub, charging ports can supply currents above
0.5 A without digital negotiation. A charging port supplies up to 500 mA at
5 V, up to the rated current at 3.6 V or more, and drop its output voltage
if the portable device attempts to draw more than the rated current. The
charger port may shut down if the load is too high.
...
....

The Battery Charging Specification 1.2 of 2010 [12] makes clear, that there
are safety limits to the rated current at 5 A coming from USB 2.0. On the
other hand several changes are made and limits are increasing including
allowing 1.5 A on charging ports for unconfigured devices, allowing high
speed communication while having a current up to 1.5 A and allowing a
maximum current of 5 A.
Click to expand...

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
Almost the first 10 years of USB were complete crap.
Click to expand...
That might be true. My first computer with USB was purchased in 2001, and I
never had problems with USB.


These days, USB mostly works. It's still obnoxious when devices can't
handle being moved between ports though, which is proof USB or
everybody that writes device drivers are completely stupid.

Does moving a scanner between my front and rear USB port really
require a driver reinstallation? WTF?
Click to expand...
In theory, no, but that's the way it is.

If you go to Device Manager, select Show Hidden Devices, and rummage through
the listings (especially Universal Serial Bus Controllers), you'll see a lot
of grayed USB devices. Many of these represent the /same/ device attached to
a /different/ USB jack.

In other words, the USB system organizes by ports rather than devices. If
you plug a device you've used before into a different port, USB doesn't know
this, and installs the driver for use by the new port. I don't know why it
was done this way.

If this bothers you, keep track of which jack you plug a device into. Make
sure that devices that often connected to the computer at the same time
don't use the same jack.

By the way, it's okay to "prune" the listing of entries for devices you're
not using any more, or are duplicates. The worst that can happen is that the
device will stop working until you remove/replug the cable. A few months
back I deleted something like a hundred entries, without wrecking anything.
 
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
Cydrome Leader wrote:

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

Cydrome Leader wrote:

Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
On Wed, 12 Sep 2012 18:34:33 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Anyone know if any USB pins other than 1 and 4, are used as part of the USB
charger protocol ? I needed a small 5 volt PSU for a little project, so I
bought one of the latest generation 'Apple' chargers from eBay, where it's
all built into a standard sized UK 13A mains wall plug. It came with a USB
to Apple lead, so I cut the Apple connector off, fully expecting there to be
only two wires - Gnd and +5v - in the cable, but there was actually 4 thin
wires. So I then assumed that they had maybe just doubled up on the wires,
as this thing is rated at 1 amp output. But again, no. All four wires were
separate, so I checked what was coming out of it. Just over 5v between black
and red, so that's ok, but measuring between black and green, and black and
white, there is also voltage. Two point something on one pair, and three
point something on the other, I don't recall the exact figures. Could they
be just 'pullup' values to keep the "data +" and "data -" lines quiet when
it has a genuine USB device connected to it ?

AFAIK, in order to pull more than 100 mA from a USB port, a device is
supposed to do a digital dance with the host to request the higher
capacity, up to 500 mA. There may be (read: probably are) dedicated
charging ports that will cheerfully source 500 mA (or more?) to a "dumb"
device without requiring the dialog.

Isn't it sad all this garbage is needed to send 5 volts down a cable?


Needing three resistors is sad?

yeah, it is.

USB is not like ethernet where adding power happened later on and there is
a chance to do weird stuff like plug two PoE switches into each other
with a patch cable. USB doesn't support "illegal" scenarios like this due
to the connectors, so any extra signalling is just bullshit to lockout
devices or make you get stuff you should not need.


A couple cents worth of resistors to turn on the port is a simple and
sensible way to protect the port. It was designed that way, not added
at a later date. Look at the data sheets for some of the hub ICs.
Click to expand...
to protect the port from what? A device that doesn't work anyways?

hub ICs and resistor networks to provide 5 volts and a few hundred mA is
just too hard?

Can anybody confirm that the clowns that made the miniDIN connector were
involved in the creation of USB?
 
William Sommerwerck <grizzledgeezer@comcast.net> wrote:
Isn't it sad all this garbage is needed to send 5 volts down a cable?

I've seen the USB 2.0 specs, and they're beyond unbelievable. You'd think
what appears to be a simple interface would take only ten pages or so to
define, but it takes 10 or 20 times that.

USB might be "over-defined", but at least it works. I can't think of a USB
product I've owned that didn't work correctly. From my point of view, this
is not an accident. Somebody did a lot of thinking to make sure there
weren't any "gotchas" in the system specification.
Click to expand...
almost the first 10 years of USB were complete crap.

every chipset for it was buggy (even big name ones like intel), it was
slow, and devices other than a mouse were really pushing it. OS support
was junk too.

My favorite knockout combination was Windows 98 on a Hitachi laptop. There
was no chance in hell anything USB would ever work on that combo.

I had some digital camera with USB 1 or 1.1. it was actually slower than
using the irDA port on the camera, which was emulating 115kb serial. yes,
an LED and photodiode behind some plastic window emulating a 1960s method
of connecting teletypes to furniture sized computers blew away the mess
known as USB.

these days, usb mostly works. It's still obnoxious when devices can't
handle being moved between ports though, which is proof USB or everybody
that writes device drivers are completely stupid.

Does moving a scannwe between my front and rear USB port really require a
driver reinstallation? WTF?
 
In article <k2t82n$oei$1@dont-email.me>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

Does moving a scanner between my front and rear USB port really
require a driver reinstallation? WTF?

In theory, no, but that's the way it is.
Click to expand...
That's almost entirely an operating-system issue... not USB per se.

It's a question of how does an application locate/identify/address a
specific USB peripheral.

USB has a tree hierarchy... controllers, hubs (possibly several layers
of them) and devices. Applications generally want to open a device
using a fixed, repeatable identifier. Depending on the OS and the
application, this identifier may be based on the bus topology (which
controller, hub chain, and port) or on the unique characteristics of
the device itself (model, manufacturer, type, serial number).

It sounds as if Windows is creating a unique, long-term identity for
the device based on both of these - the device itself, and the bus
topology to reach it - and that changing to a different port "orphans"
the identity. It might be Windows itself doing this, or the
manufacturer-supplied device driver.

Other operating systems (e.g. Linux) can assign a unique identity
based solely on the device's unique characteristics, assuming that it
has enough to make it unique (e.g. a real serial number), and the same
identity will be assigned to it no matter what port it's plugged into.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
 
Does moving a scanner between my front and rear USB port
really require a driver reinstallation? WTF?

In theory, no, but that's the way it is.

That's almost entirely an operating-system issue... not USB per se.
Click to expand...
Thanks for the explanations.
 
USB is completely stupid, from the ground up.
Click to expand...
I don't know how long you've been using personal computers, but it seems
you've never had to set up COM ports, which can be a major pain in the
toches. USB largely delivers on its promise of "plug and play". Whatever
problems it might have, they are offset by the fact that USB works with
little or no fussing.

The only problem I can remember is a product that said you shouldn't install
the driver until you've plugged in the device, when it was actually the
other way around. Or maybe vice-versa.
 
Cydrome Leader wrote:

William Sommerwerck <grizzledgeezer@comcast.net> wrote:

USB is completely stupid, from the ground up.

I don't know how long you've been using personal computers, but it seems
you've never had to set up COM ports, which can be a major pain in the
toches. USB largely delivers on its promise of "plug and play". Whatever
problems it might have, they are offset by the fact that USB works with
little or no fussing.


I used a dumb terminal before I had a complete computer, so I'm no
stranger to serial and all the goofy breakout boxes, null modem adapters
and chain of adapters almost foot long to get stuff to work. It was all
pretty stupid, but about as good as it gets for stuff that old.

I used a set of barn door hinges, C-clamped on my table as a straight
Click to expand...
keyer for morse code, before all that I have now came along. Beat that
one!

Jamie
 
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