In my recording studio I have a Focusrite 18i8 gen3 interface and a Behringer ADA8200 ADAT unit.
If I use the ADA8200 as the master clock, the Focusrite's sample rate needs to match, which I can't guarantee since sometimes I work in 44.1KHz and sometimes I work in 48KHz (and if they mismatch, no audio gets played at all, which is less than ideal). However, switching the ADA8200's sample rate is pretty unwieldy (as it's on the back panel and thus hidden inside my equipment rack), and the 18i8 will adopt whatever sample rate is requested by the software I'm running at the time regardless of what master clock it's receiving.
It seems that my best option is to have the 18i8 be the master clock source, but it doesn't provide a dedicated wordclock output or an ADAT output, which are the only two options for getting an external clock into the ADA8200.
After doing some research, it seems that the only workable solution is to convert the S/PDIF output on the 18i8 to either a wordclock source or an ADAT source. There used to be an S/PDIF wordclock extractor made by a company called "jfaudio," but they are now defunct, and S/PDIF to ADAT conversion seems to be a thing that a lot of people want but nobody has ever made.
Another possibility might be to mod the 18i8 to get a wordclock signal out of it, but of course that's risky and I haven't found any schematics or starting guides for that.
I am not opposed to building my own circuit (Arduino or otherwise) for extracting wordclock from S/PDIF, but I'm having difficulty finding anything about either protocol at anything more than a vague hand-wavy level.
Are there any existing solutions for this situation, or any resources I can use to develop my own? Or some incredibly-obvious approach that I'm missing?