question about how to flicker led in ipad iphone using connector

Experts, I want to develop an app (with accompanying hardware) that turns 2 leds (Light Emitting Diodes), in different frequencies, I found this pin out for the iphone/ipad connector link. The questions are:

1. what pin should be the best to accomplish my flickering led? pin#? and and (GND off course),
2. what function in objective C will allow me to do this?,
3. I found this site for buying the connectors, do you have a better one?

I intend to have the earphones connected as well, so the sound pins are not an op开发者_JAVA百科tion,

thank you in advance!

edit> here an example of an external flash light for the iphone light

so I ask you guys please the same question, what pin and what function is used to turn this light on?, I can take care of the frequencie generation and the electronics, thanks!

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The ExternalAccessory.framework is the best place to start. It's covered in the External Accessory Programming Topics.

Manufacturers must build explicit support into their accessory hardware for communicating with iOS. As part of this support, an accessory must support at least one command protocol, which is a custom scheme for sending data back and forth between the accessory and an attached application. Apple does not maintain a registry of protocols; it is up to the manufacturer to decide which protocols to support and whether to use custom protocols or standard protocols supported by other manufacturers.

It's basically all up to you to create the protocol but the ExternalAccessory.framework is where iOS meets the external device.

Original answer, which would sound snarky to an electronics engineer, removed. :-)