Werner's self-described USB host "hack" would significantly increase sales of Ben Nanonote. When NN is used at home or office, adding a USB hub would allow connecting a large, comfortable keyboard and a mouse.
Naturally adding USB host via Ben's 8:10 port and UBB offers a Hobbsian choice: do you want/need 802.15.4 radio, VGA, or USB host. Choices, choices. --- Ron K. Jeffries On Tue, Oct 4, 2011 at 09:03, Werner Almesberger <[email protected]>wrote: > I wrote: > > That's what I'd do, yes. UBB, a USB A receptacle, one pull-down > > resistor, and a bit of ribbon cable should get you quite far. > > Like this: > http://downloads.qi-hardware.com/people/werner/ubb/usb/concept.pdf > > Source: > > http://projects.qi-hardware.com/index.php/p/ben-blinkenlights/source/tree/master/ubb-usb/ > > On the top is the standard configuration of low-speed host and > device. The pull-up R1 indicates to the host that this is a > low-speed device. D+ has no pull-up on the device side and is > therefore pulled low by the host's R4. > > The pull-ups and pull-downs are not only used for device speed > identification, but also for driving the signals to defined > levels if neither side is driving them. > > R2 and R3 define the impedance of the drivers but can probably > be omitted in our case, since the CPU's I/O pins already have > an impedance roughly in that range. > > The UBB-USB hack is below. Inside the Ben, all signals but CLK > are pulled up. This means that we can only used CLK with a weak > pull-down (alternatively, we could try to add a strong > pull-down, but that may have unwanted side-effects.) > > The pull-down would be between GND and CLK and be soldered > directly to UBB. Then a ribbon cable would connect to a USB > receptacle. > > This setup assumes that the USB device is content with 3.3 V. > If it isn't, an external 5 V supply could be used for > development, e.g., from a lab power supply or by tapping the > Ben's inbound VBUS. > > - Werner > > _______________________________________________ > Qi Hardware Discussion List > Mail to list (members only): [email protected] > Subscribe or Unsubscribe: > http://lists.en.qi-hardware.com/mailman/listinfo/discussion >
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