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
