1. what does "precision sync" ?- can u send me A2500 custom FW with precision sync ?
You'll probably need modified code to make sure the cameras shoot as exactly the same time (within about 1mSec). Older cameras worked without the mod, newer cameras need it. For now it's not important - sync is the least of your challenges. But we will want to test to be sure it works once you have more than one camera available to do the test.
after shoot command from PC (dont open the switch / disconnect the red wire )
Sounds like chdkptp is timing out. I guess it does not like issuing a "shoot" command and not having the shoot happen right away. reyalp will probably want to answer this one. I wonder if this happens with really long Tv's too?
Does the camera also take a picture when you get the error message ?
Yes , it takes time , the LED on the camera is blinking (BUSY) for while till it shoot (~50sec)
Need to be a little more precise here.
If you issue the shoot command via ptp and then just wait (don't open the red wire), after 7 seconds you get a timeout error message on your PC, and after about 50 seconds the camera completes the shot ? Is that correct?
The LCD stays blank the whole time as well, right ?
Are you certain that the delay you see is 5 seconds and not 10?
As this seems to be a chdkptp issue and not the USB remote code timing out, I'll leave it to reyalp to decide if the exact interval is important.