[Arm-netbook] It arrived in the post just now!

[peter green]

luke.leighton wrote:
>  i don't know anything like that that actually exists.  if you mean
> "turn the USB-OTG port into USB Host (in software e.g. the simplest
> way is to change the script.fex to make it a USB Host) then connect a
> 4-port powered USB hub to it" then yes that should work absolutely
> fine.
>
>  if however you're thinking that you can power-up by providing 5V
> power on the USB-OTG interface and at the same time make some weird
> cable where the USB signals go to a USB powered up then please don't
> try doing that, it will only end in tears.
>   
Techically the "USB battery charging" spec actually defines how to make 
an adaptor for doing exactly that it's reffered to in the spec as an 
"ACA" (accessory charger adaptor). They also define a device that 
contains a USB hub and provides power to the device on the host port 
which is reffered to as an ACA-Dock. However i've never seen an ACA for 
sale and ACA-docks seem pretty rare (afaict the motorola lapdock is an 
ACA-dock)

According to the spec the ACA or ACA-dock indicates what it is doing to 
the OTG device through resistor values on the ID pin of the USB 
connector (which makes hacking things together for testing a PITA 
because you've got to find a source of micro USB plugs with all five 
connections brought out).

Further it seems that not all devices support (at least when I tried it 
on a nexus 7 with a hacked up cable it didn't work)

Of course if you control the software you can probablly force things 
even without the ID pin value being right.