I think similar approach is followed here. However, they use a phototransistor to pick up when the red eye reduction LED flashes to sync the created image file with the log entry in the FCU.
If you read through the thread for the
kap_uav.lua script you will get the history of how that was developed.
I also found this project, do you guys know anything about it (i.e. the hardware)?
I have not seen that one before. Looks like the external card activates a camera side script via PTP to "shoot" and while passing it some parameters to store on in a separate log file on the camera's SD card. That lets them associate the image name and GPS info later on.
After a quick look, it seems that with the same hardware, it should be possible to modify the camera side Lua script to utililze kap_uav.lua's customized exposure control algorithm and also to write the data to each image's EXIF info.
Unfortunately, when you look at
<this link> there is also a notice that says :
The Open CCB is not yet commercially available - we are actively seeking manufacturers. (even though this topic is archived!)