any idea how can i do that?

Try following http://www.digi.com/support/kbase/kbaseresultdetl?id=2180

Yeah, I’d like to know that too!
I have XBP24s and XB24s working all over, but when I turn on API mode (AP=1) I can’t get the loopback test to work.
I think I’ve followed all the right steps (for the API type loopback), but the devices just do not communicate.
I’m wondering it 10EC is OK for this???

Ah, I figured it out. For loopback test only the base should be API. Doh!