[linux-audio-user] noise from USB printer

Dave Phillips dlphillips at woh.rr.com
Sat Jul 22 07:28:21 EDT 2006


Hi Mark :

> Ground loop problem? As a test only, what happens if you unplug power
> on the printer, or turn the printer off?

Same noise. It stops if I pull either the power or the USB cable.

> If it is a ground loop issue - I did hear of this recently with a USB
> hard drive I think - then possibly it's a cable issue or maybe you
> could stuck a USB hub in the middle to break the loop? (Just
> guessing!) ;-)

I tried sticking a hub between the machine and the printer, it didn't 
reduce the noise at all. :(

I'm going to visit our brand-new Wal Mart to look for a 
noise-suppressive cable.

> On the off chance it's something more nefarious, what are the relative
> IRQ priorities of the USB controller vs. the sound card? I Assume the
> sound card's IRQ has a high realtime priority? If not, and it's lower
> than USB, then possibly there is some strange interaction. I've never
> run into anything like that with USB, but I have with other devices
> like a mouse, etc.

Here's the output from lspci and /proc/interrupts on the offending machine :

Output from lspci:
00:00.0 Host bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133] 
(rev 02)
00:01.0 PCI bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133 AGP]
00:07.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South] 
(rev 22)
00:07.1 IDE interface: VIA Technologies, Inc. 
VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 10)
00:07.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 
Controller (rev 10)
00:07.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 
Controller (rev 10)
00:07.4 Bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 30)
00:10.0 Ethernet controller: Lite-On Communications Inc LNE100TX 
[Linksys EtherFast 10/100] (rev 25)
00:12.0 Multimedia audio controller: Creative Labs SB Live! EMU10k1 (rev 08)
00:12.1 Input device controller: Creative Labs SB Live! MIDI/Game Port 
(rev 08)
00:14.0 Multimedia audio controller: VIA Technologies Inc. ICE1712 
[Envy24] PCI Multi-Channel I/O Controller (rev 02)
01:00.0 VGA compatible controller: nVidia Corporation NV11 [GeForce2 
MX/MX 400] (rev b2)

Output from 'cat /proc/interrupts' :
           CPU0      
  0:   62304648          XT-PIC  timer
  1:       5639          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  3:        127          XT-PIC  EMU10K1
  5:    9043743          XT-PIC  ICE1712, uhci_hcd:usb1, uhci_hcd:usb2
  7:          1          XT-PIC  parport0
  8:          4          XT-PIC  rtc
 11:      63698          XT-PIC  eth0
 12:     537858          XT-PIC  i8042
 14:      46717          XT-PIC  ide0
 15:         23          XT-PIC  ide1
NMI:          0
LOC:          0
ERR:          0
MIS:          0


I'm concerned by the USB and ICE1712 sharing the same IRQ. How do I 
reassign the interrupt ?

Best,

dp




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