Ur816c ipad

(New) iv both 2x ur816c about a week ,and im tring to make it work with my ipad pro 3gen…
Simple question ‘how to make my second ur816c apear in my daw as a slave Adat expender ,meaning having a 16chanel to record my band
But using my ipad

Hi! I am sorry but that won’t be possible. In the user manual on page 31: “When connecting an iOS device, the OPTICAL input and output are disabled. The clock source is fixed to Internal”.