Why would the same payload have a slightly different looking IEEE 802.15.4 frame three days later?

Question

I have two xbee S1s that successfully communicate with each other. But I am trying to get one of them to receive IEEE 802.15.4 frames from an Atmel transceiver. The goal, of course, is to "trick" an xbee into thinking it is talking to another xbee, when in reality it will be talking to the Atmel transceiver. The only way, as far as I can tell, to do this is to monitor the packets transmitted by an xbee using a sniffer and clone them on the Atmel transceiver.

And here are my findings:

The packet sniffer shows the following traffic when entering a single ASCII character "m" from an xbee S1:

The sniffer shows the following when sending a single ASCII character "k":

The sniffer shows the following when sending the same ASCII character "k" 3 days ago:

Aside from time stamps, why would the payload have "ad" one day and "a**23*" another day?

Would appreciate if the wireless network experts from the community could weigh in.

Answer 1

Try to get a hex dump of those payloads. I would guess that some of the * characters are unprintable ASCII and vary as well. The payload probably has different header fields, possibly including an incrementing transaction ID. Does the target device's 64-bit IEEE address appear in those bytes? How about it's 16-bit network address? Maybe sender address? You'll need to figure out the packet format, and my guess is that it contains more variable data than just the character you're sending.