Joining and credentials

Two things have to be true

A new wardrobe sensor cannot just appear on a Zigbee network. Some device has to be accepting joins, and the sensor has to be accepted by a process secure enough to trust it. Being nearby is neither of those.

Permit-join is a window

The coordinator and the routers only answer a device that asks to join while permit-join is open. It is a time-limited window, and when it closes they stop answering. A router can be told to open it as well, not only the coordinator. A device put into pairing mode with the window shut gets no answer and shows you no error.

Choosing a parent

A device that asks hears several routers that could take it as a child. The specification orders candidates by signal quality categories and other priorities, and stacks differ in the details, so there is no single rule to quote. On the bench the order is an example: signal first, then free capacity.

The nearest router is not always the chosen one. A router that is nearest but has a full child table cannot accept another child, and the sensor passes it over for the next candidate. Link quality and state decide, and distance does not.

Commissioning

After a parent accepts the device, a commissioning step decides whether the network trusts it. How that goes depends on the device, the method and the Zigbee version: a button, a code printed on the device, a scan of a code, a vendor's own flow. A press on a button is one case and not the rule.

The bench never shows a key, and not an invented one either. It shows which step happens and in what order.

Next, how paths form and change follows the sensor's report once it has joined. For the same question on Wi-Fi, see the Wi-Fi course.

Common mistakes

• Expecting a device to join with the window closed. Permit-join is time limited. Open it on the coordinator or on a router near the device, then start the device's pairing.
• Assuming the nearest router becomes the parent. Candidates are ranked by link quality, capacity and state, and a full router is passed over however close it is.
• Thinking pairing is always a button press. Commissioning varies with the device, the method and the Zigbee version. Follow the device's own instructions for its flow.