Andy Green andy at openmoko.com wrote on Mon Apr 14 13:50:27 CEST 2008 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
Somebody in the thread at some point said: | Hi, | | 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 You're right. The apeture on the case is correct only for mini USB, so it isn't quite painless. The OTG socket has a different profile. Micro AB: http://www.farnell.com/datasheets/99722.pdf Mini B: http://www.farnell.com/datasheets/83318.pdf The plastic case apeture conforms closely to the Mini B profile shape. The thing does work OK as USB host, as you say the cables are going to be an issue. - -Andy ------------------------------------------ This is a problem with the Nokia Internet Tablets as well. The main feature of the USB-OTG spec is that it *automatically* puts the device in host mode when the cable is inserted. (OTG compliant devices also allow swapping host & peripheral modes at any time during the connection, but I haven't yet seen any examples where that's particularly useful. There's also a USB power control aspect, but again the usefulness in actual practice is limited.) As the Mini A to standard A female adapters/cables are difficult to find (Mini B to standard A female are much more common), I just spliced together a couple of cables I had lying around to make my own adapter cable. It works like a charm. I have to change to host or OTG mode manually, but that's no big deal. USB-OTG devices should work fine as a standard USB peripheral. It's possible, although a bit more tricky, to make your own OTG cable with whatever plugs you need. If the device that's acting has host doesn't supply enough current for the peripheral, you can use a powered hub between them, although that results in regular USB connections (you lose OTG when going through a hub). In short, USB-OTG is more of an issue with relatively "dumb" devices than it is with devices that are basically full-blown computers in their own right (like the Neo and Internet Tablets). More info: http://www.usb.org/developers/onthego/ http://www.maxim-ic.com/appnotes.cfm?appnote_number=1822&CMP=WP-3 Mark _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
