I'm trying to let two routers to send message at the same time to test if there is data collision. the DH/DL of coordinator I set is 0/FFFF which is broadcast, and the DL/DH of both routers I set is used the source address of the coordinator. But the problem is it doesnt work.... sometimes the coordinator can only get message from only one router. I think it should be displayed both messages from the two routers. I'm really appreciate for your suggestion, thanks.