Text 48047, 74 rader
Skriven 2008-08-14 09:13:02 av Ross Cassell (1:123/456)
  Kommentar till text 48043 av Björn Forsström (2:203/614.61)
Ärende: USB
===========
Hello Björn!

14 Aug 08 10:38, you wrote to All:

 BF> Is there a current limit on the USB ports?
 BF> I have a Office Jet G85, ScanJet G 4050, USB mouse, and a USB
 BF> DVD writer.
 BF> When the mouse, G85 and G4050 are connected the DVD will be
 BF> disconnected and a USB memory will not br recognized as a USB
 BF> device.
 BF> When the G85 and G4050 are disconnected the DVD and the memory
 BF> works perfect.

A USB Root device can support in theory up to 127 devices.

The average PC on the market might sport lets say 2 USB ports on the front of
the case and perhaps 4 to 6 more on the rear. Each set of ports is technically
already hubbed off of a root device..

So the question is, are all these devices you use being plugged into the USB
ports on your PC, or are you using a external USB hub?

If you are using a external USB hub, is it a powered hub?

Does the DVD drive have its own power supply?

A typical USB port is capable of providing a device with 5 volts of power, but
many devices require more, such as printers, scanners and most external DVD/HDD
drives, although there are some small DVD drives capable of subsisting on 5
volts. However multiple devices on the same root device or unpowered hub that
require power from the USB port in use at the same time can play havoc,
similiar to what you experience, but I am not saying that this is the cause of
your problem but its possible?

On the printer, scanner and DVD drive, are you using cables that are no longer
than 16 feet in length? USB cables are typically sold in 3, 6, 10 and 16 foot
lengths but extension cables can be used, are you extending the cables past 16
feet? Dont look at the physical distance the device is from the PC, but the
actual length of the cables used to connect them? Going past 16' will result in
signal degradation, only way around this problem is to add in a powered hub
every 16' to serve as a repeater of sorts..

Have you tried, plugging in your devices into a different port?


Lets assume you have a typical cpu:

Front of Case (Root hub 1)

Port One _______________________

Port Two _______________________


Rear Of Case (Root Hub 2)

Port One _______________________

Port Two _______________________

Port Three _____________________

Port Four ______________________


Fill in what is plugged in where, including any external hubs?

==
Ross
Fidonet Feeds Or Fidonet In Your Newsreader: http://www.easternstar.info
E-mail: ross(at)cassell(dot)us | Blogs/Other Places: http://links.cassell.us
... Martin Luther King Jr, was a Republican!
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 * Origin: The Eastern Star - Spartanburg, SC USA (1:123/456)