Y-cable and USB-OTG: mutually exclusive

[Carsten Haitzler (The Rasterman)]

On Thu, 1 May 2008 08:31:16 +0800 Carsten Haitzler (The Rasterman)
<raster at openmoko.org> babbled:

forgot to say.. don't like 2 plugs on the outside though... maybe we can hide
one under the back cover or something?

(really come on -how often will u want power from charging AND need to run a
usb device as a host for a long period of time? if you have power to charge.. u
are likely @ home or office... and u can do things on your laptop or
desktop...).

> On Wed, 30 Apr 2008 19:28:21 +0200 Joachim Steiger <roh at openmoko.org> babbled:
> 
> > sorry for jumping into this thread so late...
> > 
> > we are at the point of considering having 2! external accessible usb
> > connectors for reasons of not wanting to sacrifice charging while using
> > usb client OR host as well as providing power to usb host if wanted as
> > well as having a internal debugboard.
> > 
> > this all got me thinking.. especially all this nonsense of 'usb
> > certifications' (if you ask me, do whats reasonable and helps people to
> > use stuff in the real world, and ignore all the nonsense parts)
> > 
> > - i really like my mini-usb. (for mechanical, practical and spread in
> > the real world)
> > - i have till now not seen a single micro-usb wallwart charger or carkit
> > in the real world (nor a device which uses that connector at all).
> > - the N8xx series is the only device i know i were near which does OTG
> > as far as i know.
> > 
> > thus my questions:
> > - why not put a mini-usb-b like we have now onto the device?
> > * do charging and client mode there. no host
> > * be usb compliant when it comes to 100/500mA with usb enum
> > * detect and use chargers with either id-resistor of known value and
> > thus current
> > * AND be able to detect usb charging spec (which is just nailed down
> > what was in use before and now) by checking short on D+ and D-
> > (eventually you can switch them to gpio and wiggle one and watch the other?)
> > = > compliant with all carkits and wallwarts which i know of.
> > means 'it will work' (and charge) in any case i can imagine and not
> > endanger any fuses on mainboards ;)
> > 
> > to the usb-host part:
> > we are talking about a second connector there.
> > - why not make it usb-(mini)-A ?
> > * i would rather like A due to the more widespread of cables and
> > devices, but its propably too big
> > * provide 100 or 500mA there.
> > * put a single 2-positions switch below the battery flap to switch this
> >  whole port to jtag.
> > = > would enable directly plugging loads of usb client stuff.
> > - also makes the schematic much easier. less complicated cornercases.
> > - the _only_ point where somebody needs a nonstandard cable is when
> > using jtag ((mini)-A to A). and it is only a cable, no electronics.
> > => ALL other usecases are available without any non-usb standard cables,
> > devices, pinouts or whatever. like total compliance with everything of
> > usb that makes sense AND keeping our beloved 'can do all' features while
> > still knowing what people will plug together when plugs fit and make it
> > work.
> > 
> > additional thoughts:
> > * put both connectors to one side of the case (enable docking both with
> > fixed plugs in some kind of cradle
> > * leave enough space between for silly stuff which is wider than a
> > simple connector.
> > 
> > please let me know what you think
> 
> i agree on all - mini not micro usb, and the switch sounds nice (though from
> an ID point of view sean is mentioning having the back held in by screws so
> changing that switch may be a little hard, but then again... how often will an
> end user really need jtag?).
> 
> i definitely think we need to have the usb connector at the bottom of the case
> - not the side. docking/cradles really would demand this.
> 
> > 
> > -- 
> > 
> > Joachim Steiger
> > Central Services
> > 
> > _______________________________________________
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> > hardware at lists.openmoko.org
> > http://lists.openmoko.org/mailman/listinfo/hardware
> 
> 
> -- 
> Carsten Haitzler (The Rasterman) <raster at openmoko.org>
> 
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-- 
Carsten Haitzler (The Rasterman) <raster at openmoko.org>