Q: FAQ: Controlled joining in ZigBee (Z-Stack)

Joining networks when router/endpoint wakes up before the coordinator.

If a Router / End Device wakes up before the Coordinator, the device will periodically go through a discovery phase where it searches for a network and attempts to join one that it has found. If there is no network present, or any one present will not allow the device to join, then the network goes back to sleep until NWK_START_DELAY has passed. This code is part of the ZDO and can be modified based on how you require the initial joining or commissioning behavior to work. In addition to having periodic join attempts you could also make the join attempt user triggered in response to a button press or external event. Again all of this is managed within the ZDO (ZDApp.c).