An advice about a new feature

[ChanElgin]

When something connected to the hot shoe of Canon 600D，the camera will automatically disabled the built-in wireless flash function, Can it be a way to stop this  disablement？(that is,I hope that the camera  will recognize  there's no flash installed on its top)
If some  flash light with wireless TTL function, which is not made by Canon(and the price is much cheaper), can be connected to the camera and still be able to use  wireless TTL function，it will be great(it can be used as a real TTL flash light).
I really hope the new Magic Lantern firmware can achieve this function，and it's very useful. I wish you to consider my advice，thank you.(My English is not good enough...囧，I don't know wether it's appropriate to post the topic here either ...)

[scrax]

The wireless transmission is made with the internal flash light, so if you have another flash on the camera internal flash can't be raised...
there are cheap TTL radio transmitter that are better than the light wireless way canon is using on 600D and on his flashes

[ChanElgin]

Well, I mean I want to use a wireless TTL flash as a TTL flash on the top of the camera.
When you take photos outdoor, you need a TTL flash fixed on the camera instead of a TTL radio transmitter and a  wireless TTL flash...

I'll upload some pictures to show  how to achieve this effect  later.（My method can't firmly  fix the flash on the camera,so I need a better way by software...  ）

[ChanElgin]

[scrax]

Now understood, I think it will not be easy.
don't know any way to disable that external flash switch in the flash hotshoe but i saw an event that changes from 30001 to 4030001 when it is pressed, so maybe that's a start...

[ChanElgin]

That's great! Looking forward to your research~~~