Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <1124905096.194966.294990@o13g2000cwo.googlegroups.com>,
edjohnson987@yahoo.com wrote:
> When connecting an iPod Photo to the USB port it syncs up OK with
> iTunes. However, the battery charge icon on the iPod never shows and it
> does not appear to charge. I have a version 1.06 A7N8X motherboard
> running W2K Pro. I do have the latest bios flash. There is something
> in the iPod manual about "high power" USB 2 port. Is this type of port
> available 1.06 version of the A7N8X, version 2.0, or is my MB defective?
If you go to PDF page 150 of the usb_20.pdf document,
"Figure 7-29. Power-on and Connection Events Timing" shows
that the bus voltage must be present in order for the
device to be recognized when it is plugged in. At least
that is how I interpret what I see there. This is a huge
download and a fat document, and hard to interpret all
it contains.
http://www.usb.org/developers/docs/usb_20_02212005.zip
Normal practice, is for Asus to power the port with a five
volt source derived from either +5V or +5VSB. There is a
header on the motherboard (USBPWRxx) that allows the user to
select either one of those. The choice should make no difference
to your problem, except that ATX power supplies have only 2 amps
to offer on +5VSB, so the factory default header setting
of "+5V" is the better choice in terms of getting as many
amps as possible. (It would be pretty hard to overload the
+5VSB supply, because when you do, the computer shuts off,
and you'd notice that.)
Now, once either +5V or +5VSB is selected to power a pair of
USB ports, there is a Polyfuse in the path. It will open up
in the event of an overcurrent condition. It is an automatic
fuse, that recovers when it cools off. But if I am interpreting
PDF page 150 correctly above, both devices on a connector stack
would disappear from your desktop if that automatic fuse opened.
What you could do, is probe the +5V pin on the unused port of
a USB port pair with a voltmeter, while the Ipod was plugged
into the other port. But this would be a pretty dangerous thing
to try. While using the voltmeter, you could clip the ground
lead onto a I/O connector screw, so you would only have to
handle one lead at a time.
Alternately, an optical mouse with a red LED for illumination,
could be plugged into the port above the Ipod, to demonstrate
that bus power to the connector stack is still available, even
though the Ipod refuses to see it.
If I had to guess, I'd say the Ipod was playing hard to get.
http://docs.info.apple.com/article.html?artnum=60941
The following is a document that Intel made available as an
aid to motherboard makers, to make sure they got the bus
powering right. This 628KB download is a bit smaller than the
9MB+ standards document above. At the point that the A7N8X
was made, I would think these rules would be well known.
http://www.usb.org/developers/whitepapers/power_delivery_motherboards.pdf
Paul
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