How do you tell a usb1 cable from a usb2 cable?

Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not
conclusive. I want it to work ALL the time.

So, how do you sort the pile?
The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

If you're a cable vendor, you MUST have some design guidelines
and test procedures to verify USB2 compliance.

Doesn't anybody know what those are?
mike

So, how do you sort the pile?
The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

If you're a cable vendor, you MUST have some design guidelines
and test procedures to verify USB2 compliance.

Doesn't anybody know what those are?
mike


It's mostly a marketing gimmick...especially with cables that are under 6 ft
long.

For cables over 6ft...a cable with good shielding is desirable...

I am not sure how much of a difference the diameter of the wire comes into
play...
but I'm sure a larger guage wire would not hurt anything.

So, how do you sort the pile?

ALL the cables are USB 2 cables. Those that don't work for USB 2 are
DEFECTIVE.

PERIOD - END OF DISCUSSION.

A cable that works for USB 1 and NOT for USB 2 is NOT designed that way, it
is DEFECTIVE, just like an 80 pin IDE cable that will work a CD drive, but
not a hard drive.

mike wrote:

Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

They mostly will do USB2 fine.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not conclusive. I want it to work
ALL the time.

Then you are going to have to buy new cables. There is no alternative.

So, how do you sort the pile?

Not even possible with what you have.

The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

There arent any with USB2. The most you can do is check what
the standard requires and attempt to see if an existing cable fits
that. And since the standard doesnt specify the requirements
with just the params you list there, you cant do it that way.

If you're a cable vendor, you MUST have some design guidelines and test procedures to verify USB2
compliance.

Yes, but you cant use those with an existing cable with the
stuff that stops a particular cable working perfectly wiht USB2.

Doesn't anybody know what those are?

They are in the standards documentation but wont help
you any because it isnt specified in those terms alone.
http://www.usb.org/developers/compli...letestplan.xls
is part of that, but there isnt any point in farting around with
the specific test fixtures, it makes a hell of a lot more sense
to just buy branded new cables that claim to be USB2 and
return them if they dont in fact work properly.

mike wrote:
Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not
conclusive. I want it to work ALL the time.

So, how do you sort the pile?
The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

If you're a cable vendor, you MUST have some design guidelines
and test procedures to verify USB2 compliance.

Doesn't anybody know what those are?
mike

From the standard (USB 2.0 650 pages)

*******
6.3 Cable

USB cable consists of four conductors, two power conductors, and two
signal conductors.

High-/full-speed cable consists of a signaling twisted pair, VBUS, GND,
and an overall shield. High-/fullspeed cable must be marked to indicate
suitability for USB usage (see Section 6.6.2). High-/full-speed cable
may be used with either low-speed, full-speed, or high-speed devices.
When high-/full-speed cable is used with low-speed devices, the cable
must meet all low-speed requirements.

Low-speed recommends, but does not require the use of a cable with
twisted signaling conductors.

6.4 Cable Assembly

This specification describes three USB cable assemblies: standard
detachable cable, high-/full-speed captive cable, and low-speed captive
cable.

A standard detachable cable is a high-/full-speed cable that is terminated
on one end with a Series “A” plug and terminated on the opposite end with
a series “B” plug.

A high-/full-speed captive cable is terminated on one end with a Series
“A” plug and has a vendor-specific connect means (hardwired or custom
detachable) on the opposite end for the high-/full-speed peripheral.

The low-speed captive cable is terminated on one end with a Series “A”
plug and has a vendor-specific connect means (hardwired or custom
detachable) on the opposite end for the low-speed peripheral. Any other
cable assemblies are prohibited.

The color used for the cable assembly is vendor specific; recommended
colors are white, grey, or black.
*******

That section of the USB 2.0 standard, says a "standard detachable cable"
is high/full speed. And will have a shield.

A high/full speed cable must meet (PDF page 138):

Impedance - measured with differential TDR, with other end of cable open cct.
Acceptable impedance range specified in Table 7-9 (ZO).
[ The actual data is in Table 7-12. Z0 90ohms +/- 15% Zcm
30 ohms +/- 30%. TDR has an oscilloscope-like trace and
measures impedance all along the cable, and the above tolerance
defines the space the oscilloscope trace must fit within. ]

Loss - measured with a network analyser, as per PDF page 139. Table
to meet is section 7.1.17.

7.1.17 Cable Attenuation

USB cables must not exceed the loss figures shown in Table 7-6.
Between the frequencies called out in the table, the cable loss
should be no more than is shown in the accompanying graph.

Table 7-6. Maximum Allowable Cable Loss
Frequency (MHz) Attenuation (maximum) dB/cable
0.064 0.08
0.256 0.11
0.512 0.13
0.772 0.15
1.000 0.20
4.000 0.39
8.000 0.57
12.000 0.67
24.000 0.95
48.000 1.35
96.000 1.9
200.00 3.2
400.00 5.8

Propagation Delay - measured with the TDR, as per PDF page 140.

And so on.

In other words, if you read the USB 2.0 spec, you'll find all the necessary
information. Apparently, a detachable cable is *only* supposed to be
high/full speed and shielded. Meaning there is no such thing as an unshielded
detachable cable :-) As far as the person writing the standard is concerned.

Even sticking the cable on a TDR for a moment, should immediately make it obvious
whether a shield is present or not. But physical examination can also tell
you that.

You'll find the necessary equipment expensive to rent, so you'd better have
a large pile of cables to sort.

Paul

Noozer wrote:
So, how do you sort the pile?

ALL the cables are USB 2 cables. Those that don't work for USB 2 are
DEFECTIVE.

PERIOD - END OF DISCUSSION.

A cable that works for USB 1 and NOT for USB 2 is NOT designed that way, it
is DEFECTIVE, just like an 80 pin IDE cable that will work a CD drive, but
not a hard drive.



Interesting perspective. You're welcome to your perspective.
For me...
I have cables that don't work on usb2 on some systems.
I'd like to know why, just for the fun of it and to be sure
that the cable I take with me will work when I need it to work...always.
No, I'm not gonna go buy more cables...

The particular offenders are the tiny cables that are on a retractible
spool.

Paul wrote:
mike wrote:
Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not
conclusive. I want it to work ALL the time.

So, how do you sort the pile?
The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

If you're a cable vendor, you MUST have some design guidelines
and test procedures to verify USB2 compliance.

Doesn't anybody know what those are?
mike

From the standard (USB 2.0 650 pages)

*******
6.3 Cable

USB cable consists of four conductors, two power conductors, and two
signal conductors.

High-/full-speed cable consists of a signaling twisted pair, VBUS, GND,
and an overall shield. High-/fullspeed cable must be marked to indicate
suitability for USB usage (see Section 6.6.2). High-/full-speed cable
may be used with either low-speed, full-speed, or high-speed devices.
When high-/full-speed cable is used with low-speed devices, the cable
must meet all low-speed requirements.

Low-speed recommends, but does not require the use of a cable with
twisted signaling conductors.

6.4 Cable Assembly

This specification describes three USB cable assemblies: standard
detachable cable, high-/full-speed captive cable, and low-speed captive
cable.

A standard detachable cable is a high-/full-speed cable that is terminated
on one end with a Series “A” plug and terminated on the opposite end with
a series “B” plug.

A high-/full-speed captive cable is terminated on one end with a Series
“A” plug and has a vendor-specific connect means (hardwired or custom
detachable) on the opposite end for the high-/full-speed peripheral.

The low-speed captive cable is terminated on one end with a Series “A”
plug and has a vendor-specific connect means (hardwired or custom
detachable) on the opposite end for the low-speed peripheral. Any other
cable assemblies are prohibited.

The color used for the cable assembly is vendor specific; recommended
colors are white, grey, or black.
*******

That section of the USB 2.0 standard, says a "standard detachable cable"
is high/full speed. And will have a shield.

A high/full speed cable must meet (PDF page 138):

Impedance - measured with differential TDR, with other end of cable open
cct.
Acceptable impedance range specified in Table 7-9 (ZO).
[ The actual data is in Table 7-12. Z0 90ohms +/- 15% Zcm
30 ohms +/- 30%. TDR has an oscilloscope-like trace and
measures impedance all along the cable, and the above tolerance
defines the space the oscilloscope trace must fit within. ]

Loss - measured with a network analyser, as per PDF page 139. Table
to meet is section 7.1.17.

7.1.17 Cable Attenuation

USB cables must not exceed the loss figures shown in Table 7-6.
Between the frequencies called out in the table, the cable loss
should be no more than is shown in the accompanying graph.

Table 7-6. Maximum Allowable Cable Loss
Frequency (MHz) Attenuation (maximum) dB/cable
0.064 0.08
0.256 0.11
0.512 0.13
0.772 0.15
1.000 0.20
4.000 0.39
8.000 0.57
12.000 0.67
24.000 0.95
48.000 1.35
96.000 1.9
200.00 3.2
400.00 5.8

Propagation Delay - measured with the TDR, as per PDF page 140.

And so on.

In other words, if you read the USB 2.0 spec, you'll find all the necessary
information. Apparently, a detachable cable is *only* supposed to be
high/full speed and shielded. Meaning there is no such thing as an
unshielded
detachable cable :-) As far as the person writing the standard is
concerned.

Even sticking the cable on a TDR for a moment, should immediately make
it obvious
whether a shield is present or not. But physical examination can also tell
you that.

You'll find the necessary equipment expensive to rent, so you'd better have
a large pile of cables to sort.

Thanks for the useful information.
I have a TDR and a spectrum analyzer/tracking generator. Should be a
piece of cake.
mike

Paul

Rod Speed wrote:
mike wrote:

Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

They mostly will do USB2 fine.

You have no idea what cables I have.
In particular, the roll-up cable I most want to use works the worst.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not conclusive. I want it to work
ALL the time.

Then you are going to have to buy new cables. There is no alternative.

In your experience.
In my experience, a new cable costs as much as the laptop I'm gonna plug
it into.


So, how do you sort the pile?

Not even possible with what you have.

Exactly what do I have??????? I'll save a lot of effort by using your
inventory of my stuff to update my insurance coverage.


The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

There arent any with USB2. The most you can do is check what
the standard requires and attempt to see if an existing cable fits
that. And since the standard doesnt specify the requirements
with just the params you list there, you cant do it that way.

Ok, so how does one do it?

If you're a cable vendor, you MUST have some design guidelines and test procedures to verify USB2
compliance.

Yes, but you cant use those with an existing cable with the
stuff that stops a particular cable working perfectly wiht USB2.

Quit telling me what I can't do and tell me what I CAN do.

Doesn't anybody know what those are?

They are in the standards documentation but wont help
you any because it isnt specified in those terms alone.
http://www.usb.org/developers/compli...letestplan.xls
is part of that, but there isnt any point in farting around with
the specific test fixtures, it makes a hell of a lot more sense
to just buy branded new cables that claim to be USB2 and
return them if they dont in fact work properly.

Make whatever sense you want.
I WANT TO TEST MY CABLES!!!...particularly the tiny ones that roll up
and fit in your pocket.
mike

mike wrote
Noozer wrote

So, how do you sort the pile?

ALL the cables are USB 2 cables. Those that don't work for USB 2 are DEFECTIVE.

He's right.

PERIOD - END OF DISCUSSION.

A cable that works for USB 1 and NOT for USB 2 is NOT designed that way, it is DEFECTIVE,

And there too.

Interesting perspective.

It aint a perspective, thats that the standard says.

You're welcome to your perspective.
For me...
I have cables that don't work on usb2 on some systems. I'd like to know why, just for the fun of
it

They dont meet the specs of the USB standard.

and to be sure that the cable I take with me will work when I need it to work...always. No, I'm
not gonna go buy more cables...

Only a fool would mindlessly test cables to the USB
specs instead of buying brand name USB cables and
returning them when they dont work properly at USB2.

You qualify.

The particular offenders are the tiny cables that are on a retractible spool.

Bet they are pathetically inadequately shielded and have pathetically thin conductors.

mike wrote
Rod Speed wrote
mike wrote

Started a new thread 'cause the old one went off course.

We've all got a pile of usb cables of unknown origin.

They mostly will do USB2 fine.

You have no idea what cables I have.

Dont need to.

In particular, the roll-up cable I most want to use works the worst.

Then you should stop using that cable.

Just plugging it into a device is not an adequate test.
Just because it happened to work on one system in one test is not conclusive. I want it to work
ALL the time.

Then you are going to have to buy new cables. There is no alternative.

No practical alternative I obviously meant.

In your experience.

Nope, that's what the standard says.

In my experience, a new cable costs as much as the laptop I'm gonna plug it into.

Your problem. A new cable that works costs peanuts, MUCH less than
what is required to test a particular cable against the standard specs.

So, how do you sort the pile?

Not even possible with what you have.

Exactly what do I have???????

You wont have the standard test jig that is
required to measure the cable performance.

I'll save a lot of effort by using your inventory of my stuff to update my insurance coverage.

Never ever could bull**** its way out of a wet paper bag.

The parameters that are easy to measure are
wire resistance
characteristic impedance
frequency dependent transmission loss
But what are the go/nogo criteria?

There arent any with USB2. The most you can do is check what
the standard requires and attempt to see if an existing cable fits
that. And since the standard doesnt specify the requirements
with just the params you list there, you cant do it that way.

Ok, so how does one do it?

Pay for your copy of the standard. Its all spelt out in there.

Just like it is with any standard.

If you're a cable vendor, you MUST have some design guidelines and test procedures to verify
USB2 compliance.

Yes, but you cant use those with an existing cable with the
stuff that stops a particular cable working perfectly wiht USB2.

Quit telling me what I can't do and tell me what I CAN do.

I was obviously commenting on what is practical.

Doesn't anybody know what those are?

They are in the standards documentation but wont help
you any because it isnt specified in those terms alone.
http://www.usb.org/developers/compli...letestplan.xls
is part of that, but there isnt any point in farting around with
the specific test fixtures, it makes a hell of a lot more sense
to just buy branded new cables that claim to be USB2 and
return them if they dont in fact work properly.

Make whatever sense you want.
I WANT TO TEST MY CABLES!!!...

THEN PAY FOR YOUR COPY OF THE STANDARD AND YOUR TEST
JIG AND TEST THE CABLES THAT YOU KNOW DONT WORK AND
ALL YOU HAVE ACHIEVED IS THAT YOU WILL KNOW WHY THEY
DONT WORK. YOU ALREADY KNOW THEY DONT WORK!!!!!...

particularly the tiny ones that roll up and fit in your pocket.

If you're actually stupid enough to spend that sort of
money confirming what you already know, that they
wont do USB2, you're always welcome to do that.

THERE IS NO ALTERNATIVE.