SPDIF input voltage level / optical input

For a project I would like (or actually I need to) use Toslink Optical input. A seperate converter box is not a suitable solution. So I am looking for a way to let the Khadas Tone Board connect to a Toslink optical cable.

So far I found a optical reciever, with 3.3V logic level: https://www.diyinhk.com/shop/audio-kits/83-192k-optical-spdif-receiver.html

But what is the accepted voltage / logic levels on the SPDIF RCA input?
Or is it possible to connect a SPDIF elsewhere, for example on the 40pin header?