USB Cable too long?

On 30/08/2018 16:02, Mayayana wrote:
"Fokke Nauta" wrote

| If the scanner is the problem, that it can't handle the length of the
| USB cables, it would be a problem with my pc as well.

Not necessarily, if it's just near the max length
that the scanner can handle. But it's just one
idea to rule out.

| Motherboard perhaps? Too old? USB 2.0 inputs, whereas my pc has USB 3.0
| inputs.
| Should this make the difference?
|

I've never seen problems with different machines,
except that sometimes they seem to require using
them in order. That is, #3 port may seem dead if
there's nothing plugged into #2 port.

I tried several USB ports. Didn't make a difference.

As Al said, it works when you plug it in direct.

Correct

So
doesn't that only leave the switch, a cord, or cord
length as variables? Maybe try switching the
switch connections?

I did. Changed the cables as well. No difference.

I've never used a USB switch,
so I don't know about that, but I wonder if there
could be some kind of priority glitch. For instance,
your PC turned on and somehow getting "first dibs"
on the connection. I guess you could test that by
turning off your PC and/or unplugging your PC but
still leaving the other hooked up via the switch.


It's just an ordinary switch, which connects one cable or the other.
What I'm doing is first setting the switch to the desired pc, and then
turn the scanner on. PC's are always on (Not at night).

Both pc's, on their turn, see that the scanner is on and recognize it.
But only on my pc I am able to scan.

Fokke

On 30/08/2018 15:35, Big Al wrote:
On 08/30/2018 09:26 AM, Fokke Nauta wrote:
On 30/08/2018 15:14, Mayayana wrote:
"Fokke Nauta" wrote

| Could it be that total cable length is too much?
| Why is the scanner then working allright with my pc?

I wouldn't dismiss the other two answers, but I have
found that hardware varies. And some devices will
tell you in their manuals what the length of a cable
can be.

We have a high-end Epson photo printer and a
budget, everyday printer. (I think the latter may
be HP.) Only one can fit near the computer, so
there's a 12' USB cord for the other. The Epson
simply won't tolerate that cord. The everyday
printer doesn't mind at all.

So it could be the ports, the switch, the systems....
But it's also possible that you've set it up at the
high end of the cable length it will tolerate. On the
bright side, all of the ideas presented so far are easy
to test.




If the scanner is the problem, that it can't handle the length of the
USB cables, it would be a problem with my pc as well. Same type of
cables, same length. But my system works well with the scanner.
Tried different USB inputs on my wwife's pc. Didn't make a difference.
Motherboard perhaps? Too old? USB 2.0 inputs, whereas my pc has USB
3.0 inputs.
Should this make the difference?

Fokke
But you say your wife's pc works if hooked straight in. So the port is
okay. The only variable in this argument is the switch and your wife's
USB port not compatible. I can't believe the switch only works on USB
3 but that could be an idea if you have docs on it. But most USB3 are
backwards compatible.

Real head scratcher.


Yes, it is.
It's an USB 2.0 switch. To my opinion just an ordinary switch.

Fokke

On Thu, 30 Aug 2018 19:55:11 +0200, Fokke Nauta
wrote:

To my knowledge an USB hub is to connect multiple USB devices to one pc.


Yes.


What I'm doing, is to connect one USB-device with two pc's. Not
simultaneously, but either one or the other. One can't use a hub for that.


Have you tried using a hub for that, reversing its connections? I'm
not saying that it will work, since I don't know and I also doubt it,
but it might be worth a try.

Let me ask why you want to do that. I sometimes move a thumb drive
from a USB port of my computer to one on my wife's. It's easy enough
to do that, so I've never the need for something like what you're
talking about.

On 30/08/2018 20:32, Ken Blake wrote:
On Thu, 30 Aug 2018 19:55:11 +0200, Fokke Nauta
wrote:

To my knowledge an USB hub is to connect multiple USB devices to one pc.


Yes.


What I'm doing, is to connect one USB-device with two pc's. Not
simultaneously, but either one or the other. One can't use a hub for that.


Have you tried using a hub for that, reversing its connections? I'm
not saying that it will work, since I don't know and I also doubt it,
but it might be worth a try.

No. How about the connecors, which need to be reversed as well?

Let me ask why you want to do that. I sometimes move a thumb drive
from a USB port of my computer to one on my wife's. It's easy enough
to do that, so I've never the need for something like what you're
talking about.


We have one scanner and two pc's. We both want to use the scanner.

Fokke

Fokke Nauta wrote:
On 30/08/2018 16:08, Paul in Houston TX wrote:
Fokke Nauta wrote:
Hi all,

We have an Epson flatbed scanner, V600 Photo. It is connected to an
USB switch by a cable
of 1 meter. One output of the switch is connected with my pc by a
cable of 1.8 meter.
Scanner works fine. The other output of the switch is connected to the
pc of my wife (W7
Pro 64b, mobo: ASUS P7P55D). This cable is also 1.8 meter. On this pc
the scanner is
recognized, the system bleeps when the scanner is turned on. Scanning
is impossible, it
gets stuck, the led on the scanner keeps flashing, and nothing further
happens. Doesn't
make a difference when I use Photoshop or the Epson utility for scanning.
When I connect the scanner straight away to my wife's pc with a cable
of 1 meter, it works
fine.
I use Belkin USB cables, thought they are good quality. The USB switch
is König, passsive.

Could it be that total cable length is too much? Why is the scanner
then working allright
with my pc?
What type of cable should I order to make sure the scanner works
allright with my wife's pc?

Fokke

It's possible that the scanner is not compatible with the unknown model
of König usb hub.
From the König website:
"This switch is not compatible with devices that requires a constant
connection to a computer. Usually these are devices like
multifunctionals or laser printers."


You might be right. But then again, why does it work on my pc and not on my wife's pc?
And isn't a USB not just an ordinary switch, which connects one wire or the other? Should
be fine, shoudn't it?

Fokke

Don't know why it works on one machine and not the other.
Putting "usb hub insides" into google images shows they have quite a bit of circuitry inside.

On 30/08/2018 21:57, Paul in Houston TX wrote:
Fokke Nauta wrote:
On 30/08/2018 16:08, Paul in Houston TX wrote:
Fokke Nauta wrote:
Hi all,

We have an Epson flatbed scanner, V600 Photo. It is connected to an
USB switch by a cable
of 1 meter. One output of the switch is connected with my pc by a
cable of 1.8 meter.
Scanner works fine. The other output of the switch is connected to the
pc of my wife (W7
Pro 64b, mobo: ASUS P7P55D). This cable is also 1.8 meter. On this pc
the scanner is
recognized, the system bleeps when the scanner is turned on. Scanning
is impossible, it
gets stuck, the led on the scanner keeps flashing, and nothing further
happens. Doesn't
make a difference when I use Photoshop or the Epson utility for
scanning.
When I connect the scanner straight away to my wife's pc with a cable
of 1 meter, it works
fine.
I use Belkin USB cables, thought they are good quality. The USB switch
is König, passsive.

Could it be that total cable length is too much? Why is the scanner
then working allright
with my pc?
What type of cable should I order to make sure the scanner works
allright with my wife's pc?

Fokke

It's possible that the scanner is not compatible with the unknown model
of König usb hub.
From the König website:
"This switch is not compatible with devices that requires a constant
connection to a computer. Usually these are devices like
multifunctionals or laser printers."


You might be right. But then again, why does it work on my pc and not
on my wife's pc?
And isn't a USB not just an ordinary switch, which connects one wire
or the other? Should
be fine, shoudn't it?

Fokke

Don't know why it works on one machine and not the other.

I haven't got a clue either...

Putting "usb hub insides" into google images shows they have quite a bit
of circuitry inside.

Yes, USB hubs do. But my USB switch is a simple switch. Connecting one
wire to the input connector or the other wire.

Fokke

On 8/30/2018 8:00 AM, Fokke Nauta wrote:
Hi all,

We have an Epson flatbed scanner, V600 Photo. It is connected to an USB
switch by a cable of 1 meter. One output of the switch is connected with
my pc by a cable of 1.8 meter. Scanner works fine. The other output of
the switch is connected to the pc of my wife (W7 Pro 64b, mobo: ASUS
P7P55D). This cable is also 1.8 meter. On this pc the scanner is
recognized, the system bleeps when the scanner is turned on. Scanning is
impossible, it gets stuck, the led on the scanner keeps flashing, and
nothing further happens. Doesn't make a difference when I use Photoshop
or the Epson utility for scanning.
When I connect the scanner straight away to my wife's pc with a cable of
1 meter, it works fine.
I use Belkin USB cables, thought they are good quality. The USB switch
is König, passsive.

Could it be that total cable length is too much? Why is the scanner then
working allright with my pc?
What type of cable should I order to make sure the scanner works
allright with my wife's pc?

Fokke

Exchange PC connections on switch and observe if that exchanges which PC
works.

--
Zaidy036

On 8/30/2018 8:00 AM, Fokke Nauta wrote:
Hi all,

We have an Epson flatbed scanner, V600 Photo. It is connected to an USB
switch by a cable of 1 meter. One output of the switch is connected with
my pc by a cable of 1.8 meter. Scanner works fine. The other output of
the switch is connected to the pc of my wife (W7 Pro 64b, mobo: ASUS
P7P55D). This cable is also 1.8 meter. On this pc the scanner is
recognized, the system bleeps when the scanner is turned on. Scanning is
impossible, it gets stuck, the led on the scanner keeps flashing, and
nothing further happens. Doesn't make a difference when I use Photoshop
or the Epson utility for scanning.
When I connect the scanner straight away to my wife's pc with a cable of
1 meter, it works fine.
I use Belkin USB cables, thought they are good quality. The USB switch
is König, passsive.

Could it be that total cable length is too much? Why is the scanner then
working allright with my pc?
What type of cable should I order to make sure the scanner works
allright with my wife's pc?

Fokke


--
Zaidy036

Ken Blake wrote:
On Thu, 30 Aug 2018 19:55:11 +0200, Fokke Nauta
wrote:

To my knowledge an USB hub is to connect multiple USB devices to one pc.


Yes.


What I'm doing, is to connect one USB-device with two pc's. Not
simultaneously, but either one or the other. One can't use a hub for that.


Have you tried using a hub for that, reversing its connections? I'm
not saying that it will work, since I don't know and I also doubt it,
but it might be worth a try.

Let me ask why you want to do that. I sometimes move a thumb drive
from a USB port of my computer to one on my wife's. It's easy enough
to do that, so I've never the need for something like what you're
talking about.

A "hub" has active regeneration in the path. The upstream
is the host, the downstream is the peripheral.

Upstream
|
|
packet regeneration
| | | |
Down Down Down Down
Stream Stream Stream Stream

A "mechanical switch", doesn't need anything.
This could also be implemented with QuickSwitches
or transmission gates or something similar.
The total cable on either side ("path length")
cannot exceed 15 feet. If you put 15 feet of cable
on upstream, 15 feet on downstream, that's 30 feet total
and too long. Only if the switch happened to have
digital regeneration (effectively, be a switch with
a 1-port hub built into each path), could you
support 15 foot cables on either side. I've not
seen a photo of what's in these things, to know,
but the price suggests a cheesy mechanical switch.

Upstream1 Upstream2
| | | |
D+ D- D+ D-
| | | |
\ \ / /
\ \ / /
Mech
Switch A-B
| |
D+ D-
Downstream
| |
To USB Printer

That's my interpretation, and the above
assumes USB2. I don't know how or if,
all the same solutions exist for USB3.

USB3 has TX+ TX- GND RX+ RX- === 5GHz interface USB3 rate

+5V D+ D- GND === 480Mbit/sec USB2 interface

and the 5GHz part is similar in design to
PCI Express or SATA differential signaling.

The USB2 four pin interface is not nearly
the same quality. In its lowest speed modes,
it runs single-ended and the wiring is
also half-duplex, which doesn't help matters.

The nice thing about USB3, is it's full duplex,
you can TX and RX at the same time, and the role
and function of each pin is more fixed (the RX pair
can have a 100 ohm resistor permanently affixed
as flyby termination, that sort of idea).

Paul

Fokke Nauta wrote:

We have an Epson flatbed scanner, V600 Photo. It is connected to an USB
switch by a cable of 1 meter. One output of the switch is connected with
my pc by a cable of 1.8 meter. Scanner works fine. The other output of
the switch is connected to the pc of my wife (W7 Pro 64b, mobo: ASUS
P7P55D). This cable is also 1.8 meter. On this pc the scanner is
recognized, the system bleeps when the scanner is turned on. Scanning is
impossible, it gets stuck, the led on the scanner keeps flashing, and
nothing further happens. Doesn't make a difference when I use Photoshop
or the Epson utility for scanning.
When I connect the scanner straight away to my wife's pc with a cable of
1 meter, it works fine.
I use Belkin USB cables, thought they are good quality. The USB switch
is König, passsive.

Could it be that total cable length is too much? Why is the scanner then
working allright with my pc?
What type of cable should I order to make sure the scanner works
allright with my wife's pc?

Is it actually a USB switch or is it a USB hub? Are there switches
(mechanical or software-controlled) as to which ONE output of the USB
switch will currently be connected to the USB port on the PC to which
that USB switch is connected? That is, can only one USB device be used
at a time with the USB "switch"?

If only one USB device on the output side of the USB switch can be used
at a time then it is a switch. There would be some means of selection
which output port got connected to the input port of the switch, and the
other output ports are disconnected. If all USB devices are [expected
to be] concurrently accessible that are connected to the output of the
"switch" then it really is a USB hub. Is it really a hub and there are
multiple switches on it to simply disable/unpower the individual output
ports?

Got a model of the USB switch? You mentioned "Konig" but they've had
several different models of USB switches some of which are discontinued.
At Konig's site, the only one that I found they currently produce is:

https://www.konigelectronic.com/comp...h-black-795543
which warns:
This switch is not compatible with devices that requires a constant
connection to a computer. Usually these are devices like
multifunctionals or laser printers.

That is used to share a USB device (printer, scanner, etc) to 2
computers. That is, its input port goes to the USB device and its
output ports go to the USB ports on 2 different computers. That way,
when you press the toggle button, the one USB device gets toggled
between the two computers' USB ports.

That USB switch itself requires no drivers. It merely mechanical (well,
electronically) performs a change in pathing between the one input port
from the USB device to the two output ports to the computers. I'm not
sure the switchover of the 5V power (coming from the PC's USB port)
would be smooth. Which PC's USB port would be supplying the 5V power
during a switch? Does it have some electronics to smooth out the power
switch when changing which PC to which the USB device is connected
(which means it would need a capacitor to maintain power during the
glitch at the time of the switch). That momentary loss of 5V power
during the switch could force the USB device to initialize again.

The Epson V600 scanner has its own A/C power supply, so it doesn't need
and probably doesn't use the 5V from the USB connection. However, it's
possible the USB 5V power is used when the USB device goes into sleep
mode (to power the sensing logic in the USB device to know when it
should wake up).

The total length of the USB connection would be from the USB device's
USB port through the length of USB cable connected to it to the USB
switch, the pathing internal to the USB switch, and then the length of
USB cable from the USB switch to whichever PC the switch was currently
configured to connect.

USB device (scanner) - 1 meter USB cable - USB switch - 1.8 meter USB
cable - computer's USB port. That's just a tiny bit over 2.8 meters.
The maximum length for a USB2 cable is 5 meters for full-speed USB
devices, 3 meters for low-speed USB devices. To go further means you
need to insert an active USB extender aka repeater (amplifies and cleans
up the signal and ensures 5V gets to the USB device - cheap ones don't
do the latter, they may recondition the signal but pass on the power
as-is). USB 3 has a max length of 3 meters. According the Konig's
specs, their 2-port USB switch only handles USB 2.

There is also the issue with handshake timing; see:
https://superuser.com/a/1105099

If the switch between computer's for the 5V power isn't smooth or the
switch provides its own power to the USB device, a glitch could result
in the device reinitializing which will be a hell of lot longer than the
link failure timeout. The Konig switch has no A/C power adapter, so it
must switch the 5V power from the USB cable to one computer to the 5V
power from the USB cable to the other cable but without dropping the
power. I don't know what your USB device(s) has(have) to cover very
short power glitches (outages). Konig's specs are minimal, so no
information on how they smooth the 5V power switchover. Their "support"
page, after entering "CMP-USBSW2" and selecting their USB switch, just
dumps me back to their product page which tells me nothing about HOW
that switch operates. Back in the mechanical switch era, you needed a
make-before-break switch to ensure no disruption in power. All they
note is the statement that I commented under the link above for their
product page.

Besides the issue of switching the power to the device from the two
computers, how about USB enumeration? When you toggle, the same device
will now appear as a new connect to the computer to which you toggled.
Handshaking takes some time and there isn't an instantaneous bong-bing
tone notifying you the device has sent its presentation data and becomes
recognized. That's probably why Konig mentions their switch won't work
with devices that require a constant connection (once connected). Those
devices don't tolerate disconnects without having to reinitialize again.

They dis-recommend you using their USB switch with multifunctional (MFC)
and laser printers. Is a scanner that different, especially if it
expects to use 2-way communication to report status of the device? They
provide a passive USB switch. I've seen powered USB switches that claim
"Stable connection: USB 2.0 sharing switch with a separate micro female
port for optional power, optimizing its compatibility with more devices,
such as ...", noted at:

https://www.amazon.com/UGREEN-Select.../dp/B01MXXQKGM
(but you have to provide the power adapter that has a micro USB
connector)

By providing their own power to the USB device(s), they don't encounter
glitches in the source USB's 5V power during the switch. That one
happens to be a USB3-capable switch.

Have you tried powering down the scanner BEFORE using the USB switch to
toggle between PCs. PCs are up, power down the scanner, press the
toggle button on the USB switch, power up the scanner. Else, it looks
like you need to use a powered USB switch (not USB powered but line
powered). Alternatively, add a powered USB hub between the USB switch
and the USB device (scanner). I've seen those sell new for under $10
but that's on the low-end, like:

https://www.newegg.com/Product/Produ...9SIA6SY2B99168
No spec on the adapter to know how much load it can handle across all 7
ports, and it's too small to handle a full load on all of them.

https://www.newegg.com/Product/Produ...82E16817111402
They give a 3A rating for their power adapter to spread across all USB
device ports.

https://www.newegg.com/Product/Produ...82E16817182057
Although the same price as the Dlink, their adapter puts out only 2A.

I think I've seen powered USB hubs that had a 48W power converter
(probably for 4-port USB3 powered hub with a 2.4A charging port) but
that's a large brick sitting in the middle of the cord, not a walwart
hanging from an outlet.

On 08/30/2018 11:36 AM, NotMe wrote:

USB 3 puts out more power than USB 2, get a powered USB hub.

I suppose you know it doesn't actually put out more power unless the
connected device requests more power.

In the same way, a 100mA nightlight plugged into a 20A household circuit
will draw 100mA, not 20A.

Also, those numbers (500mA for USB2, 900mA for USB3) are MINIMUMS. As to
maximums, I've heard the connectors can handle 5A.

I've known USB2 ports that can supply more than 2A.

On 08/30/2018 12:55 PM, Fokke Nauta wrote:

[snip]

To my knowledge an USB hub is to connect multiple USB devices to one pc.
What I'm doing, is to connect one USB-device with two pc's. Not
simultaneously, but either one or the other. One can't use a hub for that.

It does seem unlikely to work.

For one thing, you'd have 2 or more controller devices connected
together, which a hub is not designed for. Also, you'd need custom
cables to connect them.

Fokke


--
Mark Lloyd
http://notstupid.us/

"Death is an experience best avoided, as it makes reliable internet
access difficult to obtain."

On 08/30/2018 01:00 PM, Fokke Nauta wrote:

[snip]

Both pc's, on their turn, see that the scanner is on and recognize it.
But only on my pc I am able to scan.

Fokke

The scanner could be getting confused, since it's connected to 2
different computers. Try resetting the scanner after switching.

--
Mark Lloyd
http://notstupid.us/

"Death is an experience best avoided, as it makes reliable internet
access difficult to obtain."

On 08/30/2018 01:32 PM, Ken Blake wrote:

[snip]

Have you tried using a hub for that, reversing its connections? I'm
not saying that it will work, since I don't know and I also doubt it,
but it might be worth a try.

How would you connect it, to try that? USB (other than USB-C) uses
different connectors for host and device.

Let me ask why you want to do that. I sometimes move a thumb drive
from a USB port of my computer to one on my wife's. It's easy enough
to do that, so I've never the need for something like what you're
talking about.

My use for a USB switch is to quickly disconnect the keyboard when a cat
jumps on it.

--
Mark Lloyd
http://notstupid.us/

"Death is an experience best avoided, as it makes reliable internet
access difficult to obtain."

On 08/30/2018 01:56 PM, Fokke Nauta wrote:

[snip]

No. How about the connecors, which need to be reversed as well?

Cut 4 good USB cables in two to make the 3 custom cables needed to try
something with a minuscule change of working.

Let me ask why you want to do that. I sometimes move a thumb drive
from a USB port of my computer to one on my wife's. It's easy enough
to do that, so I've never the need for something like what you're
talking about.


We have one scanner and two pc's. We both want to use the scanner.

In that case, I'd prefer a standalone scanner with a USB port or memory
card slot.

--
Mark Lloyd
http://notstupid.us/

"Death is an experience best avoided, as it makes reliable internet
access difficult to obtain."