Wrong Mini-USB-Jack

thomasg thomas at gstaedtner.net
Mon Apr 14 13:39:24 CEST 2008


In IRC we were wondering why the Freerunner, being a USB-OTG-Host (according
to the OTG spec), only has a USB Mini-B interface (black jack).
This means that only USB-Mini-B cables can be used in that jack, what causes
that USB-OTG cables can't be used.
The Freerunner is clearly a device that should have a Mini-AB port (grey
jack), means it can be used as a client (over standard Mini-B plugs) or as a
OTG-Host (over standard Mini-A plugs).
It is only as small issue - the electric layout of both jacks is basically
the same (means the Mini-B-jack can be replaced without changing layout or
something else with Mini-AB) - but it has some major sideeffects:
The Freerunner will _not_ be USB-OTG-compliant, means this great
feature can't be advertised for enduser products (as you may have
noticed: most vendors advertise USB-OTG heavily if their product
supports it).
2. It will be hard to use the OTG-feature at all, because a
standard-compliant adapter is mostly mini-A to standard-B (or similar).
There might be some cheap mini-B to standard-B adapters, but they are not
standard-compliant and may cause problems with some specific devices.
3. Without being able to advertise the feature endusers won't even know that
this device can act as USB-OTG-host, because the black mini-B jack implies
that the device is only a client.
Like said before: it would be possible to change the jack without changing
the board layout at all. But as the mini-AB-jack has a minimal different
shape it would need to change the breakout in the case, so I don't see any
chance to get this done in the current stage.
We just wanted to point that out, to give OM Inc. a chance to fix this


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