Tag Archives: usb

USB Debugging

Some link useful to poke around our USB devices:

Debugging USB Problems
USB docs from

In brief

Listing the USB devices:



cd  /sys/bus/usb/devices/
ls -l

or (raw)

lspci | grep USB

Seeking for errors (it’s useful to remember 🙂 )


Talking with the device

Writing some parameter to the device (see docs to know what you’re doing):

echo 0 | sudo tee /sys/bus/usb/devices/usb2/power/autosuspend_delay_ms

or (as root)

# echo 0 > /sys/bus/usb/devices/usb2/power/autosuspend_delay_ms

ot talking to the module:

modprobe usbcore autosuspend=5

Resume a not working USB port

There’s a lot of people (mee too) that at some point has one/all USB port(s) not working.
I found that should be something related to the voltage protection of the port. It will be fixed turning off the PC (from the power supply) for 1 or 2 minutes.

If you cannot turn off the pc there’s another way: remove the usb modules then load them back:

# rmmod uhci_hcd
# rmmod ehci_hcd
# modprobe ehci_hcd
# modprobe uhci_hcd

Remember that UHCI is for USB1 and EHCI is for USB2.

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Posted by on 2014/04/24 in sys


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Speed comparison table

Did you already know that USB3 is theoretically fastest than SATA2? =)

USB1 1.5 Mbit/s
USB1.1 12 Mbit/s
USB2 480 Mbit/s
USB3 4.8 Gbit/s
SATA 1.0 1.5 Gbit/s
SATA 2.0 3 Gbit/s
SATA 3.0 6 Gbit/s
eSATA 3 Gbit/s
eSATA 6 Gbit/s
FireWire 400 400 Mbit/s
FireWire 800 800 Mbit/s
FireWire S800T 800 Mbit/s (uses a LAN cat.5 cable)
FireWire S1600 1600 Mbit/s
FireWire S3200 3200 Mbit/s
Thunderbolt 20 Gbit/s
LAN 10 10 Mbit/s
LAN 10/100 100 Mbit/s
LAN 10/100/1000 1000Mbit/s
802.11a (20Mhz) 54 Mbit/s
802.11b (20Mhz) 11 Mbit/s
802.11g (20Mhz) 54 Mbit/s
802.11n (20Mhz) 72.2 Mbit/s
802.11n (40Mhz) 150 Mbit/s (using 1 spatial stream…max 4 spatial streams => 600 Mbps)
802.11ac (draft)
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Posted by on 2014/02/12 in sys


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