Zigbee Multicast example program oddities

Greg Richter · Joined: 15 Feb 2008 Posts: 7 Location: Ellijay, GA

The example code in the CCS guide has a quirk with Multicast that I'm trying to work around. The CCS example 14 works a treat from the SED going back to the Coordinator, you can hold the button down and just blaze away watching the LED activity light flicker. I did a simple Unicast to device 0, and it's solid.

Going from the coordinator to the SED with a Multicast message is not reliable if you push the button more than one a second or so. The example code exhibits this problem, which is a surprise!

Anyone else seen this? Anyone using Multicast successfully? Everything in the kit pretty much came up and worked easily, but Multicast. Seems to hang in the stack someplace and times out if you do more than a packet a second.

Works if you go SLOWLY, though.

Anyone else working on this?

THANKS!

-G
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Greg Richter · Joined: 15 Feb 2008 Posts: 7 Location: Ellijay, GA

One more bit -- looks like there are ACK packets coming back and you can't send another before the first gets ACK'ed. Sniffing it from the RF side.

Off to check the ACK parts of the stack, I suppose.

Still open to ideas, though!

-G
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Madness takes it toll; please have exact change.

Greg Richter · Joined: 15 Feb 2008 Posts: 7 Location: Ellijay, GA

Looks like for each Multicast message from the Coordinator there are three packets -- the one you sent, the reply and the acknowledge.

Slow the data rate down to almost nothing. The Unicast messages are high rate, but no ACK. I think this must be intended for command and control -- high reliability, low rate.

Anyone have some insight on this? If not it's deep into the Ember specs sheets, which sounds like negative fun!
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Madness takes it toll; please have exact change.

Greg Richter · Joined: 15 Feb 2008 Posts: 7 Location: Ellijay, GA

Got this sorted -- FYI all:

Multicast does quite a lot of thrashing in the Ember stack and is, in fact, slow as molasses. Unicast is blazing fast, so you're better off doing the multi's yourself unless you have 100's of nodes.

-G
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Madness takes it toll; please have exact change.