USB PD has nothing to do with this – that is for much higher power applications such as charging laptops (up to 75W), and was introduced in 2012 – long, long after the various mobile device manufactures had to come up with their own way of doing things. Very few devices use USB PD.
Apple created their own standard way back when because they had no choice. The USB spec only catered for 500mA and that was that.
You could argue that it would have been more logical for the other manufacturers to follow Apple’s lead given that they did it first, but they chose the easy way out (shorting the pins).
which everyone but apple complies to.
That, however, is where the problem lies.
If you don’t want to support Apple stuff, you can just join together D+ and D- and you are done. Everything will work, and will charge up to 1.5A or 2A (not sure which). Apple stuff will charge up to 0.5A, which is OK for phones, or for the bigger stuff if it is turned off at the time.
Peter wrote:
whether the device is the “Chinese standard” (and wants the D+ and D- shorted)
This is the official USB power delivery standard, which everyone but apple complies to.
It’s news to me that there’s something specifically “chinese” about that standard…
This is for anoraks only 
I have just come across a chip called TPS2511DGNR which implements a USB charging outlet. This chip determines, using surprisingly crude means which does not involve any USB traffic, whether the device is the “Chinese standard” (and wants the D+ and D- shorted) or the Apple device (and wants specific voltages applied to the two wires).
Reading the description of how it does it answers the many repeating questions as to how to make a usable multi-device USB charger.
I bet you all the “intelligent” USB chargers on the market use this chip or something similar.
I don't think it's anything to do with ASUS motherboards. It works on three different Dell computers that I tried!
Fascinating...
My guess is that ASUS motherboards, of a certain vintage or later, have their USB port implemented with a chip on which the two data lines are directly addressable as to setting specific DC voltage levels.
Plus a means of increasing the normal ~600mA USB current limit.
Peter,
Here is the application that allows me to charge my iPad from my PC USB port.
I've no idea what it does, but it might be worth trying with your testing to see if it helps you. If it works, it might lend a clue as to what's going on.
dp
I think that charging adapter above cannot possibly do anything other than something with the two data pins.
For Apple, it would put a voltage divider on them.
For Lenovo (or Galaxy?) it would just short them together.
The problem with shorting them together and connecting the Lenovo Tablet2 is that the T2 will then try to draw up to 2A, and the USB port will do "something funny" because it can't officially output more than 0.5A.
OTOH the T2 might be sensing the voltage, and drawing up to 2A only if it is above say 5.2V.
I do suspect there are some crossed wires inside the original 30-pin cable
I would not think so, because - unless the cable is a special "charging cable" - ultimately the device has only the four USB pins to work with.
I am just ordering an adjustable DC-DC converter for my plane power unit, so I can get 5.50V.
my experience with Galaxy Tab - it´s not only about the right power/volts/ampers, I do suspect there are some crossed wires inside the original 30-pin cable. If you simply plug this 30pin cable into a normal USB port on your PC, the tablet is not charging. But once you plug a convertor (like this one - http://dx.com/p/usb-charging-adapter-for-samsung-galaxy-tab-black-151322) into the same USB and the 30pin table into this converted, your tablet gets charged. Some ASUS 10 inches are doing the same. So lenove might be the same. The latest of Samsung Tab 3 should have microUSB, so hopefully it´s going to be harmonised for future
Yes; I saw that table.
It is disingenuous as to the extent to which the "charge slowly" is really "charge so slowly it is barely perceptible" 
It is also very hard to find 5.2V USB power units. I bought one from Amazon but it is 5V...
The upper limit on USB is 5.25V so maybe a 5.25V unit, with thick cable, is the way to go if one wants to be able to charge other stuff from it.
