Parameters for continuous transmission from one ZB to another

XBee & XBee Gateway XBee - Zigbee
1

Hello world.

I’m new to this forum as well as the zigbee protocol. But in development of a robotics project, there are some questions :wink:

I’m currently working on a Point-to-Point Setup with 2 XBee Series 2 Modules. These are the ones my university usually uses for controlling robots. My task is to measure the energy levels between 2 XBees during communication. Thus I’m going to use XBee Moduls without antenna but the RP-SMA connectors and (later) own antennas with the same connector. The setup is:

XBee1 (Body) -> Power Sensor -> Antenna 1 [ over the air ] Antenna 2 -> Power Sensor -> XBee2 (Body)

Now I understand that all XBee Modules of Series 2 run the ZigBee specific firmware which is less superior to point-to-point throughput than raw IEEE 802.15.4 - but that shouldn’t be the point for now :wink:

I’m now triing to achive a maximum energy level (which surely will be less than max. level given in the data sheet) for the most possible time. Thus I need a XBee1 which is contiuously “firing” data and a second which is receiving this but does nothing than excepting (and ignoring) that garbage data. Flow Control shouldn’t be an issue because I don’t need the data, I’m just interessted in the energy levels.

For achieving this, I figured out the following tasks:

  1. Disable Device Discovery to not abort transmission for seeking possible new devices - I have no idea how to do this
  2. Disable ACK and waiting for RX okay messages - I’m planning to use broadcast mode for this
  3. Using the highest possible power leve - Parameter PL=4
  4. Collision avoidance should be disabled - Parameter CA=0

Questions:

  • Is there any point I have forgotton?
  • How does the receiving XBee handle the data? Is the buffer just overflowing so I don’t need to mind (data is just lost)?
  • Are the assumptions above correct?
  • What else can you suggest to achieve something like a contiuous transmission?
  • How do I increase throughput and minimize wait times?

I should mention that using other xbee modules is not possible. The project plan says it has to be these ones. But is there the possibility to downgrad to IEEE 802.15.4 firmware if it would have a performance plus?

Oh, and by the way, does anyone know a good file transfer software for xbee?

Thanks for reading this long text and thanks for your help! :slight_smile:
~Bjoern

2

#1 - the only way I know of to disable route discover is to set up source routing, which gets complex.

#2 - Broadcast mode will basically kill your ZigBee, since it will cause communications to stop for about 5 seconds. You need to use unicast, so set the DH/DL on one unit to match the other’s SH/SL.

I don’t think the ZB (or S2/S2B) Xbee cannot be downgraded to pure 802.15.4, and the Xbee running 802.15.4 is a different hardware CPU so that firmware cannot be loaded on the S2/S2B.

3

Thank for your reply.

I’m now into it for about 2 weeks and just recently found out that Broadcast isn’t really doing it for myself :smiley:
With Unicast and without source routing I achieved some reasonable results. May be better with source routing currently there is no time to test…

It may be interessting that the “transmission method” has more influence on the energy than playing with the XBee parameters. The best result I achieved with Packages of 64 byte data looped for every millisecond. I guess that keeps the buffer overflowing and thus provides the most continuous transmission.

EDIT:
I made a measure for 40s runtime. It shows that, regardless of variied xbee parameters, broadcasting follows the following algorithm:
… and so on with these times:

  • broadcast large = 2,5s
  • broadcast small = 1,7s
  • break 1 = 2,7s
  • break 2 = 8,5s

May be interessting some day [:-/]