I have heard people using OTG cable and a USB cable to charge one mobile from another mobile. I was wondering, Could I use the micro USB port directly to power external devices like LEDs.
I cut up the adapter wire and connected the micro USB in my mobile.
The external 2 leads have no output at all.
I searched on the internet to how to turn on the power of the micro USB in mobile. I didn't find any material.
I searched app store to find an app that uses a protocol to power on the USB port. But No results
How can I do it?
Best Answer
If one wants to turn a phone/tablet into host mode, the (ID pin) must be grounded. It is done in USB cable, in the overmold. The device-kind of USB cable has this pin floating. Unfortunately, a normal cable does not have this pin exposed, so you need a special "OTG adapter" cable, which has the ID pin grounded. Then you might be able to turn your mobile device into HOST mode, and it will output 5V on VBUS pin (Red wire). You can safely count on having at least 100mA from it, which can lit-up a substantial LED chip.
But I wonder why do you need an external LED when any phone has a built-in one, as a photo flash? There are lots of apps that use it as a flashlight...