I've done my synchronised follow focus project for a taken lens and anamorphic adaptor, but now I miss a button that can start a video recording. I assume it can be done via Sony's cable. I found this connector online here
Also I found this small analysis. done by Sebastian
I have a Zhiyun gimbal which already has this function. But it is quite an expensive thing and I don't want to disassemble it. I'm sure it has to be a simple solution. Do you have any ideas how to start?