On Sun, 21 Jan 2007, Koen Kooi wrote:
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Harald Welte schreef:
On Thu, Jan 18, 2007 at 10:23:24AM +0100, Sven Neuhaus wrote:
Since everyone is drooling about the next iteration of the Neo which is
exptected to include WiFi, I figured I'd add a request for USB 2.0. This
allows us to use a USB VGA adapter
(http://www.tomshardware.com/2005/06/08/add_a_monitor_using_usb/ - Linux
driver available!). A VGA port enables the Neo2 to replace a laptop for
doing presentations (in some cases) and you could even watch movies stored
on its microSD card (or streamed by a BluOnyx) on a battery powered HMD! :-)
Thanks, this has actually already been on our wishlist for a future
generation of our phones.
The main problem (with more powerful SoC) is not to provide a USB2.0
host port in the device. The main problem is power. You need a pretty
powerful DC/DC step-up converter to provide the 5V power supply to the
USB bus. And you have to provide at least up to 100mA - but to support
all devices, 500mA.
Newer SoCs like the omap2 series feature a charge pump for +5V to get at least
detection
working. That would simplify things a lot since the hub doesn't have to provide
power
'upstream' anymore.
Another thing to keep in mind: with 500mA you'll drain your 1200mAh batter in
little over
2 hours with USB *alone*.
Of course in the case of VGA, we presume you have AC power nearby and can
provide external power to the USB device via something like a powered USB hub.
No, it's not super elegant, but it works. Trying to find the right balance
between low power/long battery life vs. fancy power-hungry USB devices
requires this sometimes.
Michael
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