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Zigbee, Thread & Matter DISCUSSION
I bought two XBee modules expecting them to be "Zigbee radios", and they do pass serial data between two Arduinos. Now I would like one of them to read a commercial Zigbee temperature sensor, and it does not see the sensor at all.
Are XBee and Zigbee the same thing? Which XBee models actually run Zigbee, and what would it take to talk to off-the-shelf Zigbee devices?
XBee is a product family and form factor from Digi: a radio module with a 20-pin, 2 mm pitch footprint and a serial interface. Zigbee is a networking standard. Some XBee modules run Zigbee firmware; others run plain IEEE 802.15.4, Digi's own DigiMesh, sub-GHz protocols, Wi-Fi or cellular, all in the same footprint.
The old Series 1 modules are 802.15.4 only and are not Zigbee, even though they are often sold under that name. The Series 2 family (S2, S2B, S2C) and the XBee 3 can run Zigbee firmware. Series 1 and Series 2 modules cannot talk to each other over the air, so first identify exactly which modules you have.
Two modules passing serial data does not prove Zigbee compatibility at the application level. In transparent (AT) mode the module simply carries bytes from its UART to the address set in DH/DL, inside a Digi-specific profile. A commercial sensor speaks a public profile (Home Automation or Zigbee 3.0): it expects to join a network with a particular security setup, then be configured through Zigbee Device Object and Zigbee Cluster Library messages, and it reports temperature as an attribute of the Temperature Measurement cluster (0x0402), a signed 16-bit value in hundredths of a degree Celsius.
None of that happens in transparent mode, which is why the sensor is invisible.
With a Zigbee-capable XBee it can be done, but it is real work. The module must be the coordinator, run in API mode, and be configured to use explicit addressing frames, because you have to set the endpoint, cluster ID and profile ID of every message yourself. Security must be enabled with the link key that the target profile expects for joining; the exact register settings are listed in Digi's Zigbee documentation.
After the sensor joins, your microcontroller code has to answer its discovery requests, configure reporting for cluster 0x0402 and parse the attribute reports. You are effectively writing a small Zigbee hub.
If the goal is just to read commercial Zigbee sensors, a purpose-made coordinator is far easier: a USB Zigbee dongle on a small computer running open-source gateway software handles joining, security and device quirks and publishes readings over MQTT, which an Arduino or ESP board can consume.
Keep the XBees for what they are good at: a simple, robust serial link or a private mesh between your own boards. Two wiring notes for that use: the modules are 3.3 V parts (supply and logic), and the 2 mm pin pitch does not fit a breadboard, so use an adapter board. In API mode each frame starts with 0x7E, followed by a two-byte length, the frame data and a checksum, which makes it easy to address many nodes from one coordinator.
