[maemo-developers] N900 usb host + power charge

From: Igor Stoppa igor.stoppa at nokia.com
Date: Sun Sep 20 22:02:16 EEST 2009
On Sun, 2009-09-20 at 20:44 +0200, Gil Quim (Nokia-D/Helsinki) wrote:
> Hi, 
> > > > I plan to create a proposal for the push n900[1] and I plan to
> use the 
> > > > usb port. I have the following question. 
> > > > When the device is in usb-host mode it should of course provide
> power does 
> > > > it? Is it possible to charge the device while it's in usb-host
> mode? 
> The N900 comes without USB host mode. When I asked I was told that the
> limitation comes at hardware level. 

I can confirm this. The most reasonable setup would have been to provide
the A connector, but only gadget mode working forthe sales release, then
in a SW update to provide full spectrum support.

Then enters the USB certification with all its mass of quite often
bizantine, obsolete and plain braindead requirements.

One of them being that the certification with A connector can be passed
only if full functionality is provided by the SW.

In this case I propose that complaints are directed to the USB
consortium. I have really come to doubt that it's actually protecting
the consumers' interests in nowadays scenario.

> The reason for this decision was the complexity of providing support
> for charging, PC connectivity and USB OTG efficiently through the same
> Micro USB port within the project deadlines.

Add to that several HW bugs that were discovered during the development
and needed workarounds.

>  We needed to make choices and the decision was to sacrify USB OTG and
> concentrate on the essential use cases of charging and connecting to
> the PC, bringing the N900 to the market in its due time. 

Although noone really liked the choice we had to make. We do use our
products and as consumers we are aware of the limitations sometimes we
have to apply.


Cheers, Igor


Igor Stoppa
Maemo Software - Nokia Devices R&D - Helsinki

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