unpowered usb host idea (hack)

Robert Michel openmoko at robertmichel.de
Mon Jan 22 19:41:02 CET 2007

Salve Derek!

nice idea :)

On Mon, 22 Jan 2007, Derek Pressnall wrote:

> I realize that the reason the usb host port is unpowered is because
> the phone runs at something like 3.6 volt, and powered usb requires 5
> volt, which would add the need for dc-dc converters.  So, I've got an
> idea...

and another, someone could play with usb flash-memory and lower the
power suply of this usb device down to 3.6 volt. I could imagine,
that it will still work.

> What about adding a power tap next to the usb port, running at the
> phones native voltage?

So under the battery cover we could place a small switch to give 3.6 
volt to the usb connector - maybe together with a small red led to 
warn (when warning is neccessary). 
Next hack - using a cheap usb flash-memory and spend this memory
a mini USB connector fit into Neo1973.

> This should only be a matter of adding an
> additional connector (and possibly protection circuitry).  Then, an
> adapter cable can be manufacured seperately that has a usb mini-A and
> power tap connector on one end, and a full-sized usb-A on the other,
> with the dc-dc circuit inbetween?  This way, it leaves the potential
> for powered external devices without complicating the phones
> circuitry.  Of course I realize that can't be included in the first
> production run, but possibly an idea for the followon product.

But you could influence some hardware hackers, can't waiting untill
Neo1973 v.2 ;)

Happy hacking,

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