What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices?
What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices? ...  I am hoping to figure out which method provides the best compatibility with all USB devices.


It is for practical purposes impossible to make a truly universal charger using any combination of unchanging shorts or resistors on the USB charger or target device data lines because you are contending with manufacturers who are attempting to stop you doing exactly what you are trying to do. For example, Apple implement a number of charging control schemes using various combinations of resistor dividers, arranged so that only a "matching" power supply and target equipment will work together. While arguments could be advanced that such arrangements allow optimum charging performance, it is not obvious how this can be the case for Lithium Ion / Lithium Polymer batteries and a more than adequate degree of charging control can be and is achieved by many other manufacturers without using such techniques. An example of one such Apple arrangement is provided below.  

However, by walking in the footsteps of others who have already investigated this area you can achieve a reasonably good compromise. 

Many manufacturers do not publish specifications of their custom arrangements and the best you can do is either analyse their products yourself or learn from those who have done this already and who kindly make their knowledge available.

One such source is the documentation for the Lady ADA / ADA fruit Mintyboost USB charger.
This is more a saga than a tutorial!!! :-). You can start at the end and work back to find how the latest version uses what they know to maximise compatibility of start at the early accounts and follow their development path. Both approaches are valid depending on how much you want to know.

Mint Boost home page
Overview
Walk through of design process  - of value to designers  

Here The mysteries of Apple device charging tells you about, well, the mysteries of Apple device charging - and some other useful material along the way.

Ugh / Wow! - one Apple resistor arrangement. This is from an official iPhone 3GS charger: 





Here is their version 2 compatibility list which is worth looking at if you are trying foir a universal solution, as it lists a number of examples where the standard charger does NOT work but where a "cable hack" allows it to work fully or partially.

eg the above takes you to special cases such as the Samsung D series "hack" here or  the RAZR V3 modifications here



Here is a list of results using the version 3 Minty Boost with a range of cellphones
If you emulate their interface you should be able to achieve similar compatability.

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Update - late 2016:

USB Dedicated Charging Port Controllers:

SE user florisla has noted the existence of 'new' ICs aimed at providing dedicated USB charging port capabilities. He notes as an example the TI
"TPS2513A-Q1, TPS2514A-Q1 USB Dedicated Charging Port Controller"  

The best way of summarising its capabilities are a look through the summary given on its data sheet - see below: