[maemo-developers] USB Host - Class 1 Bluetooth

[From: Allen Brown]

I think you didn't understand what I was saying. I'm not saying
the device will draw more power than your injector can handle.
I am saying that turning the power on and off is a part of the
protocol. And messing with this can break things.

Also the host (i.e. Nokia) may not allow a device to come on
if it reports needing more than the host *thinks* it is capable
of.  Not sure about this.  When I was reading the USB spec I
was focussed on the electronics, not the software.

If you can your hands on a copy of the USB spec, do so.  Unfortunately
that may be difficult.  They want you to pay money to play in that
game.
-- 
Allen Brown
http://brown.armoredpenguin.com/~abrown

> I don't think the power should be an issue as Bluetooth adapters
> shouldn't be much more demanding that other USB devices that people have
> got working with the 770.  I am using a circuit similar to this one,
> http://www.hcilab.org/projects/nokia770/nokia770.htm. I will test my
> circuit with other simpler USB devices with comparable power usage but I
> think the problems will be more related to software than hardware. I
> don't have much experience with drivers on Linux so that is the bit were
> I am worried I might have overlooked something crucial.
>
> Cheers,
> Dan
>
> Allen Brown wrote:
>> This is tangential to what you are asking about, but I think you
>> could run into a problem with your power injector. It's been a
>> few years since I read the USB specs, but as I recall the host
>> knows, and makes decisions based on, what power is available.
>> Also it switches that power on and off depending on what state
>> the "bus" is in.  There could be problems if the actual power
>> doesn't match what the host thinks it is.
>>
>