I poked around some more. Unfortunately, nobody posts connection diagrams these days, but one can also draw some conclusions from the the more high-level descriptions and from problems people run into:
http://www.amazon.com/Micro-Y-Cable-extra-power-supply/dp/B00EJP5XR2 "Please note that the extra power goes into the peripheral device, not into the android device itself." One customer commented "it doesn't pass power from micro usb female to rest of cable" Also many others found that their Micro USB device wouldn't get charged, which is consistent with not having a connection between Micro.VBUS and the VBUS shared between the two (M/F) full-sized A. (However, this could also be caused by the problem described below.) http://www.amazon.com/Micro-Cable-Power-Galaxy-Samsung/dp/B00CXAC1ZW This one is more interesting. The following comment suggests that the charging issue many (but not all) observed here as well is merely because this cable doesn't tell the device on the Micro side that it's okay to draw 500 mA: http://www.amazon.com/review/R200RG3J9IQR75/ref=cm_cr_dp_title?ie=UTF8&ASIN=B00CXAC1ZW&nodeID=2335752011&store=wireless This would be normal and make sense. But it also means that the warning that devices won't charge with a given cable doesn't necessarily imply that it won't work for our purposes. So, dear Chinese cable makers, this is the sort of cable we'd like you to make (shield not shown - should be like GND): http://downloads.qi-hardware.com/people/werner/anelok/tmp/y-cable.pdf Source: https://gitorious.org/anelok/anelok/source/doc/y-cable.fig A few considerations: - most of the Y-cables I found are fairly short, apparently designed for laptops as power source. Would be nice to have a bit of extra length, in case the power-providing port is further away (PC under the desk, etc.) - the cable inevitably violates some rules. Here are some of them: - as far a I understand it (too lazy to check the standard :-), ID must be grounded if the connector is Micro A and it must be open if the connector is Micro B. What would be most convenient for Anelok is Micro B with ID connected to GND. Fortunately, it seems that the industry is already conspiring to do just that. - one probably shouldn't inject power into a Micro A upstream port without first asking nicely. - using this cable to connect devices that draw 500 mA without prior communication (bad but common), the resulting load on the PC side may be 1 A. Fortunately, not an issue with Anelok, which is happy with just a few mA. I haven't found a cable that meets exactly these specs, but the B00CXAC1ZW from above may be close. Would be nice if someone within easy shipping range could get one and measure how things are connected in there. - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
