I am wondering if it is fully compliant to Accessory Charger Adapter (ACA) specified in the Battery Charging 1.2 specification:
"Accessory Charger Adapter (ACA)
As Portable Devices (PD) get smaller, it becomes more desirable for the PD to only have one external connector. If the only connector a device has is a USB connector, then a problem arises when the user wants to attach the device to a charger at the same time as it is already attached to something else.
Consider a PD that has a single connector, which can also acts as a handheld PC. When such a device is put into an ACA-Dock, it would act as a host to various USB peripherals, such as a DAC, hub, keyboard, mouse, etc. However, while in the ACA-Dock, the device should also able to charge at the same time.
To inform the PD that it should act as host and draw current, the ACA is required to pull the ID pin to ground through a resistance of RID_A (124k)."
Received my new soldering station yesterday, and tonight built me a crude but real world usable OTG + charging cable. In addition to the micro usb-b for the S3 and the mini usb-b for a DAC, it has an additional usb-a connector to hook up to an external usb powersource.
This will allow me to play music via external DAC & use satnav while driving my car without draining my phone battery (the music isnt much of a drain, but satnav with the screen at a useful brightness level...)
Once I find some connectors that I like enough I'll make a nicer finished one, or a few, or maybe a few more and sell some...
It should be interesting to test your cable with other Android device than the S3.
Android specifications should formally include ACA, one step further from OTG.
Edited by DanBa - 5/3/13 at 12:33am