I’ve been using my freshly built dropcontroller for a week or so now. First with my mirrorless Fuji and now with my DSLR Canon.
I notice with both of them that they act as if the shutter button is always ‘partly’ depressed. Not enough to try and autofocus but enough that, for instance, I can’t bring up the menu on the Canon while the dropcontroller is plugged in – it ‘sees’ it and closes the menu right away. Same with image preview – it acts as if the shutter button is partly depressed and clears the image preview right away.
Could I have made a poor connection with the optocouplers that could cause this?
You don’t say what optocoupler you are using but it would be worthwhile double checking what connections it uses. Not all are the same.
If you have a voltage meter, check the voltage going in to the optocoupler and if that is OK check that it is switching.
The easiest way to check that the chip is working is by using a 3V battery, an LED, and a small resistor (100 ohm or similar). Connect the LED to the camera side (with battery and resistor)of the optocoupler then trigger as usual and see of the LED blinks.
I would also double check the connections used for the camera trigger.