On Fri, 12 Sep 2008 14:20:13 +0200, Matthias Apitz <[EMAIL PROTECTED]> wrote:
> one question to the community: normally you can't switch easy between > normal USB mode, i.e. a host is talking to a USB device, and > host-to-host mode where two computers are talking to each other; the USB > FAQ even warns not to connecting two computers without any kind of USB > bridge, because this could damage the computers; see here: > http://www.usb.org/about/faq/ans5/ > > how is this electrically organised in the GTA02 that I could just use a > gender > changer to switch between host-to-host mode or host-to-device mode? > > thx > > matthias You cannot "just" use a gender changer. As you already perceive, that's just the physical connection being adapted. Take a few minutes and read through http://wiki.openmoko.org/wiki/USB_host and http://wiki.openmoko.org/wiki/Specialized_USB_cables - the gist of it is that you use a coupler or non-standard cable for the physical connection, and settings in the kernel (configurable on-the-fly, of course) tell the Freerunner whether it is USB Device or USB Host, and whether to expect 5V over the USB to charge & power itself, or to provide 5V over USB to power devices. There are also some clever things that can be done on this front that aren't exploited yet, like sensing a resistor's presence or absence and automatically switching things around. I wrote a shell script to let me choose (manually) among the various configurations more easily - when asked to go to 'power-providing' host mode, it checks for 5V presence on the USB port and refuses to send out 5V while it is so. I expect similar functionality will appear soon in the form of an applet. (context menu from the USB tray icon, perhaps?) As an aside: It'd be helpful if we could use a short standard term to differentiate: Host mode providing power vs Host mode permitting charging. Given the non-standard nature of Host mode communication on top of device-mode power, I figure there's no existing standard. "powered host mode" is descriptive but potentially confusing - what is 'powered': the Freerunner or the devices... Any suggestions, anyone, or someone know of a (short) existing term in use? j _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community