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MC13234, 802.15.4 RF Performance Drops Unexpectedly

Question asked by Matt Iwamura on Nov 14, 2018
Latest reply on Dec 3, 2018 by Matt Iwamura

I've been working with the MC13234 MCU + wireless transceiver, and have encountered seemingly random drops in radio connectivity. I've been running experiments with roughly 100 boards running simultaneously, reporting in roughly once every 10 seconds. Over the course of a night I will fail to see a few of these boards report in for 30+ minutes, until they inexplicably start reporting again. After running several permutations of this experiment, I no longer suspect this is a software bug for the following reasons: 

1. If I have another wireless receiver running, not involved in acknowledgements but simply acting as a "sniffer", I will often see the "failed" boards' reports on the "sniffer" but not on the output from the main receiver.

2. In the time where a board may be failing to get its reports in, the other hundred or so boards report in fine, so it does not appear to be a software bug that keeps all reports from coming in, and also not a result of external interference, which I would expect to affect all boards equally.

3. In one experiment, the boards were programmed to power cycle in the event a board failed to get any report in for 5 minutes. Upon power cycling, the board would fail to reconnect to the receiver for possibly 10s of minutes up to a couple hours, though the requests to join may be seen by the "sniffer" in that timeframe.

4. The dropouts in reporting are sometimes correlated with a drastic drop in LQI immediately preceding or following a "no signal" event.


It's my suspicion that something is happening internal to the RF transceiver of the MC13234 that is causing the radio to go temporarily "out-of-whack". Perhaps the output power is dropping, or the frequency is shifting slightly, such that the main receiver is no longer hearing reports, but the "sniffer" still can.


I'm wondering if this is potentially an issue with the part known internally to Freescale/NXP, and if there is a potential workaround. I know there are several indirectly addressed registers that manage some of the radio specifics (e.g. shifts in frequency, configuring output power), but I haven't been able to find any official documentation about them, only references in the comments of Freescale-provided code used to configure the radio.


Any help or insight into what could be going on would be greatly appreciated.