Create a ZigBee network with only one coordinator and one end device (Direct Join Request)

Hello,

for several reasons, i'm interested on create a network between only one coordinator and one end device. I know when the coordinator start the network, it choose a free PAN ID and the the join permission is enabled for a specific time.

The problem is that i don't want several end devices belong to my network. To avoid this, i tried to use the "direct join request" from the coordinator to the end device, but the z_status for this function was "ZNwk Invalid Request". In which cases it can be used? Is it a good idea to use this function to create my network?

Thanks you!

Regards, David M.L.