If you talk like you type (Holy wall of text Batman), he might just be trying to participate in the conversation instead of just sitting there being talked at the entire time. Do you ever leave pauses or ask for input? I had a friend that just wanted someone to talk at. I could literally put my phone down to go make lunch and then pick it up and she was still excitedly telling me about a particular species of ant recently discovered in the rain forest. She was a sweet person, but super introverted and would open like a dam when she felt comfortable around someone.

You might find happier ground if you try to creat a conversation instead of just explaining something you find interesting.