Hi Loveitspicy. Sorry for not getting back to you, but I hadn't seen your reply before today.
Anyway I have just tried to grind a couple of Cardomoms and it seems to do an OK job. I think more would grind better as opposed to just spinning around the grinder.
I gave it about 4, 5 second bursts which took care of most of it.
The image shows the couple of bits that were left un-ground against 2 cardomoms for scale, but the rest was reduced to powder so these bits could easily be sieved out.

Hope that helps