USB D+ / D- Signalling for USB and AC charge modes.
After some measurements and tests i have the following infos to share with you all.
FOR ANDROID DEVICES:
If you apply 5V to the Vcc+ and ground the other 3 wires (D-, D+ and ground) so all of them have 0V = ground, then device is going to have USB mode supply.
If you apply 5V to the Vcc+, and connect ground and leave the D- and D+ wires on air (without connecting anything - insulate them), then device is going to have USB mode supply.
If you apple 5V to Vcc+ , connect the ground, and any different voltage values on D- and D+, the device is going to have USB mode supply. You can do it with voltage dividers or pass D- and D+ signals through different resistors (over 60K Ohm).
If you apply 5V to vcc+, connect the ground and give same voltage to D- and D+ , the device is going to have AC supply mode. In order to have the same voltage on D- and D+ you have to connect those together (green and white - middle pins on PCB interfaces), BUT YOU HAVE TO LIMIT THE CURRENT through a resistor connected to +Vcc 5V. (over 60K Ohm). So you go from +Vcc 5V, connect a resistor over 60K ohm, and have the other resistor end attached to D- and D+ all connected together.
FOR APPLE DEVICES:
For apple devices you don't have much of a choice. In order to charge any apple device you have to supply with voltage dividers the Data pins D- and D+ with specific voltages, and of course the +5V Vcc and ground. The specific voltages is 2,6V on D- and 2,1V on D+.
You can achieve this with 4 resistors , 2 resistors on 2 voltage dividers between 5V and ground. 56K and 47K is proper values. The larger resistor gets more voltage on it with respect to the ground, so if you connect 5V --> 56K in series with 47K and ground, the middle point of the resistors is going to be the 2,1V with respect to the ground and if you connect 5V--> 47K in series with 56K and ground, the middle point is going to be 2,6V with respect to the ground. So you give 2,6V (2nd case) to D- and 2,1V (first case) to D+.
TESTED ON IPOD 2ND, 5TH, IPHONE 3G / 3GS, IPAD 1st.