XBee S2 star topology

Wireless & IoT
1

I’m sure I’m missing something simple. I have two (with more to come) XBee S2 configured like this:

Coordinator

Modem = XB24-B

Function Set = ZNET 2.5 COORDINATOR AT

Version = 1047

PAN ID = 1116

DH = 13A200

DL = FFFF

Node

Modem = XB24-B

Function Set = ZNET 2.5 ROUTER/END DEVICE AT

Version = 1247

PAN ID = 1116

DH = 13A200

DL = 4076970B (the SL of the coordinator)

I can send data from the node to the coordinator, but not from the coordinator to the node. If I change the DL of the coordinator to the SL of the node, I can send data that direction, too (but that won’t work when I add another node).

Any ideas?

Thanks much!

2

I have been debating the same recently.

It seems to me there are two options.

The easier is to broadcast from the coordinator to the PAN broadcast address (0000FFFF IIRC). Anything sent to that address /should/ appear on any devices listening to the PAN. This does however introduce a significant latency (~3s in my setup). Not really an issue if you aren’t going for real time control.

The other is to manually control the target address with whatever controller you are using. Easily achieved using AT commands, but it makes the backend significantly more complex. I would check out the code here http://code.google.com/p/xbee-arduino/ for examples of how to control the xbee.

Hope that helps.

3

Change the DL on the coordinator to 0 and you should be all set. There’s a variety of ways of accomplishing this addressing by the way. My book covers them, as does the product manual. For example, check on ATNI and ATDN for a system that uses text names.

4

Do keep in mind that broadcasts on XBee Series 2 networks are generally a bad idea. With both the ZNet firmware and the ZB firmware the broadcast will be propagated three times by each node in the network. This can cause A LOT of traffic on even a moderately sized Series 2 network. Contrast this with a Series 1 network where the sending node is the only node to transmit and it does so once. Keep in mind that this is by design, the broadcast behaviors are defined by the ZigBee protocol.

And incidentally, nobody should use the ZNet firmware any longer. The ZB firmware is much more stable, faster, and officially supported by Digi!

Happy hacking!

5

I guess I made things much more difficult than necessary. In X-CTU, on the “Modem Configuration” tab, I hit “Restore” to get the Modem Parameters and Firmware back to the original state. Then, I set the PAN ID and Node Identifier on both XBees. That’s it. They work!

6

Great. Just wanted to second Jordan’s comment about upgrading from the ZNet firmware to the much improved ZB firmware. Nobody should be running ZNet anymore if they can help it. The only reason Digi still offers radios in this format is for systems that are too large to physically manage the upgrade. But if you can plug your radios into X-CTU, then by all means leave ZNet behind!

7

Be mindful that if you don’t want/need ZigBee mesh networking (e.g., you want a simple star topology, or point to point), XBee Series 1 is a better choice.