Hi, I was in the same position with the same hid dcctech relay device.
Here's how you can get it to work:
1. In the shutter port in the GPhoto driver, put
/dev/hidraw0 - I found I had to edit the xml file in home/.indi to get it to remember the setting - for some reason it always defaulted back to /dev/ttyUSB0 every time I changed it.
2. You need to edit the gphoto driver to send the correct command to the dcctech device. Follow the
instructions on building
from source, but right after you clone the 3rd party drivers repository, edit the file /indi-gphoto/gphoto_ccd.cpp You only need to change 2 lines:
line 649, change to:
uint8_t close_shutter[3] = {0xFD, 0x01, 0x00};
and line 1224, change to:
uint8_t open_shutter[3] = {0xFF, 0x01, 0x00};
3. Finish the rest of the instructions to build from source as written.
You might want to create a copy of the existing gphoto driver instead of just editing it in place, but the above should get the relay working. Mine is now working great!
Hope this helps,
Joe