I've added shutter control in my Fork at github.com/ken-self/indi-3rdparty.git
Checkout branch asidslr
You'll need to build from source as it is not yet ready for pushing to the nightly builds. Some refinement needed but the basic operation looks ok. I can only test by attaching a LED to the relevant GPIO pin.
It needs some work at the shorter exposures and exposures with decimal places.

Read More...