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2530 sensordemo application - behaviour

Anil Shalu
Prodigy 90 points
Other Parts Discussed in Thread: Z-STACK

Packet sniffer show multiple data request from end device (sensor) to a co-ordinator in addition to temp and voltage data sent by end device. Why end device is requesting data from co-ordinator and what it is requesting? Is this a proper working? Also, many a times request /response packets   are repeated even if sender is receive a acknowledgement for a first requets/response. Can anybody throw some light on this behaviour? To conserve battery on the end device, I would like to have minimum duplicate packet flow.

Thank you in advance.

 

  • 0
    TI__Prodigy 550 points

    Hello

    Are you referring to the periodic Data Requests that are sent by the end device to its parent (in your case the coordinator)?

    These messages are used by end devices to poll their parents to check whether data has arrived for them while they were asleep to save battery. The parent then uses a so called pending bit in the MAC acknowledgment to indicate whether data is available or not. If it is it will send it straight away and the end device will remain in RX to get it.

    You can adjust the polling rate by using the function NLME_SetPollRate() described in the Z-Stack API pdf that comes with the Z-Stack documentation. If you want you can even turn it completely off in case you know that the end device should never receive data.

    To learn about ZigBee and the usage of the Z-Stack please have a look at the Z-Stack documentation (after installation from www.ti.com/z-stack it can be found in C:\Texas Instruments\ZStack-CC2530-2.2.0-1.3.0\Documents

    There is also some good training material for ZigBee on the following page: http://tiexpressdsp.com/index.php?title=Low_Power_RF_Solutions_Workshop

    BR Kite

     

  • 0 in reply to Kite
    Prodigy 90 points

    Hello,

    Thank you for a reply and pointers to disable polling by end device.

    I still have part of my initial query unanswered. Can you throw some light on that also?

    Multiple data requests are sent,  by an end device,  one followed by another (2-4) within a short span of time (which is less than poll interval) even though router/coordinator does not have any data for it.

     

    Thanks in advance.

     

     

  • 0 in reply to Anil Shalu
    TI__Prodigy 550 points

    From the provided info it is difficult to see what might be the cause of what you are seeing and what exactly you are seeing.

    Could you post a screen shot of the sniffer log (e.g. just use ALT+PrintScr and than paste it to MSPaint and save it as jpg file and then include it in a post)?

    It looks to me that the 2-4 following data requests (if they come that quickly and have the same sequence number) are sent as the end device did not get the MAC ACK from the coordinator; hence it is doing the MAC level retries. However, this could be caused by two things: 1) the coordinator does not get the data request hence it does not ACK it 2) the coordinator send the MAC ACK but the end device does not receive it, hence repeats the data request.

    What LQI is shown is in the sniffer / how far are the nodes away from each other? What Z-Stack version are you using? What HW are you using, a CC2530ZDK?

    /Kite