Y-cable and USB-OTG: mutually exclusive

Joerg Reisenweber joerg at openmoko.org
Tue Apr 29 09:31:39 CEST 2008

Andy Green schrieb:
> Somebody in the thread at some point said:
> |> Could we use the debug port for this ?
> | :) :) :)
> | VERY GOOD idea!!! :)
> | Ok, this one will work for sure, I'll keep an eye on it.
> |
> | Having a 1.Xmm coax power connector on the outside to allow for everyday
> | regular use with *very* usual off-the-shelf power adapters is a
> | different thing, that's to be decided upon by product *design* (Sean_M-P
> | in the end?). I like the idea, but seems there's not much support from
> | anybody else. Nevermind.
> Standing orders are to make stuff simpler, less connectors (er... except
> debug) less everything, more function.  So the debug USB port for power
> idea goes well there, although the confusion aspect is increased if
> people use both connectors routinely.

Yea, but "keep it simple" not exactly means you have to open the case to
insert a connector to debug port (now GTA04 can't lie flat on desk
anymore, because debug is on backside), just to apply power when sth
like a WiFi stick, USB-memstick, USB-drive... etc is connected to GTA.

Also for "less [connectors|*]": we completely get rid of the annoying
Y-cable issue with a convenient power concept that's not blocking USB.
We don't need to supply any proprietary USB-charger (47k) any more.
Thats -2 vendor specific built-to-order (=expensive) items we have to
throw into the accessory bag, instead we add one dirt cheap standard
5V-supply for every country where we are allowed to go without
USB-charger :-) (there were rumors about China just allows USB, nothing
Less connectors doesn't mean it's going to be simpler then - obviously.
Nor will it be more economic in all cases, nor more convenient.

Confusion of end-user by 2 identical connectors, one of them, the really
hard to find one, for (virtually everyday) power for host mode and
useful for nothing else but (highly sophisticated) debug, the other for
power *only* when not in OTG-mode, but you can do everything else with
it... :-/
My 0.02EUR: A no-go, a no-NO-go. The appeal of simplicity of a coax
power connector you probably find 10000 times more "chargers" for it
everywhere in he world than for USB (e.g. my old nokia charger), you
simply can't beat that.

> The pcf50633 also has this "adapter" concept that we should look at
> deploying for debug USB power input, it's not used in GTA02, that'd be
> pretty neat.
Yep, but know what: I just can't find it anymore, anywhere in the
datasheets (50633|50606), in circuit diagrams of GTA01/02... nowhere :-(
Already started to doubt my own memory. Wasn't there a ting like
'charging 1A only via power-adapter, USB can only do 500mA'??? Some FET
aso? Swear I seen this some months ago...
Anyway, we may hook up as many power rails as we like, just decoupling
them and testing individually (A/D) for voltage.


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