This typically happens when there is a lot of data being received over the link. When the XBee stops responding, many times, querying the XBee kicks it out of this state. However, occasionally the XBee is completely locked up and the XBee has to be reset. This change handles these conditions by periodically (if not naturally occuring) querying the XBee. If during any query, the XBee does not respond within a certain number of attempts, the XBee is reset.
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