I've been hunting through the net and found a simple circuit that will act as a remote for the GH2. It effectively emulates a half press and a full press.
However I find that with this, the external microphone is not enabled. I've been wondering if this is something a firmware hack could address or do I have to modify the circuit further.
Listening to some test clips back it seems that the external microphone is contributing a little when the 'half press' button is operated, leading me to think that the mics are getting mixed through resistance.
A possible experiment is to change the resistance between pins 3 and 4 to work out at which point it decides that the external microphone should be used.
My application is a thumb operated remote on a 'FigRig' mounted GH2 with hopefully a Rode Video mic giving me more directional pickup.
OK, so this morning I took apart a remote and substituted the resistance values until I observed various results.
So, taking the resistance between pins 3 and 4 (i.e. the furthest from the tip of the 2.5mm connector) I found:
50-40K --- the GH2 knows that there is an external remote 10-4K --- the GH2 sees a 'half press' and initiates auto focus if an autofocus lens is attached, if not the 'QMenu' disappears from the screen. 2.5-1.8K --- if you enter this value momentarily the GH2 will start recording 330R - 0R --- the GH2 enables the remote microphone
Further Experiments
From To Result Open 2K Nothing Open 120R External Microphone Enabled 4K7 2K Nothing (didn't expect this) 47K 2K Starts recording 2K 120R When Recording - Nothing :( 2K 120R When Idle - External Microphone Enabled
Therefore I deduce the following logic.
a) For the remote function to work, the GH2 has to see around 47K before it will recognise any button press. b) For recording to start there must be a transition from a higher resistance to around 2K c) The external microphone can only be enabled from Idle (i.e. this cannot happen whilst recording)
I therefore, therefore conclude that we'd need a firmware change to get the external microphone and remote functions to operate simultaneously.