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CC2530: ZNP strange af_data_request packet delay

Daniele Coati
Intellectual 270 points

Part Number: CC2530
Other Parts Discussed in Thread: Z-STACK

Hello,
i have a zigbee network with about 10 routers with ZStack 3.0.1 connected to a CC2530 ZNP coordinator.
The coordinator sends periodically (about every 5 minutes) some zcl read/write attribute messages (with APS ack) to check the status of the devices and also needs to send back some information when a report from a router is received.
I noticed that sporadically a message directed to a router takes a long time (5-10 seconds) before seeing it over the air (checked with Ubiqua packet analyzer).
More in details, the host sends an AF_Data_Request through the uart connection with the znp that is instantly acknowledged by the znp with the synchronous response; then about after 10 seconds the zigbee packet can be observed over the air with the sniffer.
The aps ack is also sent and received instantly after this.
What can cause z-stack to delay sending a packet for this long time? Can it be caused by external interference? Is there some z-stack parameter that can improve the situation?

  • 0
    TI__Guru**** 222347 points
    Hello Daniele,

    Are you using the default ZNP settings? What percentage of data request commands contain this delay? Is there much network traffic at the time you notice this behavior? The MAC layer CSMA-CA will back off the network and delay sending a message if it detects too much network activity, this can be controlled in mac_spec.h and mac_pib.c in accordance with the MAC API.

    Regards,
    Ryan
  • 0 in reply to Ryan Brown1
    Intellectual 270 points

    Hello Ryan,
    thanks for the feedback.
    Yes I am using the default znp settings and the traffic on the zigbee network is normal.
    I cannot reproduce the issue reliably, i can go a few days without noticing any delay, and then for an hour a few packets (about 10%) start to be delayed.
    What is the maximum amount of time that a packet can be delayed before the znp reports an error with the default settings? Are there other situations in which the z stack will delay a packet?
    I can also provide a log from the packet analyzer, but the situation over the air when it happens seems pretty normal.

    Best Regards,
    Daniele

  • 0 in reply to Daniele Coati
    TI__Guru**** 222347 points
    Hi Daniele,

    Packets will be delayed if the ZNP is under a great deal of computational stress but I can't imagine this being the case. Have you tried increasing the heap size? Provide a znp/gateway log and notice if there is a zmemerror. Otherwise, what about testing on a different channel? processors.wiki.ti.com/.../Zigbee_Known_Issues_and_Proposed_Fixes

    Regards,
    Ryan
  • 0 in reply to Daniele Coati
    TI__Guru**** 222347 points
    Hello Daniele,

    Did my response help resolve your issue or do you have more information to provide?

    Regards,
    Ryan