def idle_task(self):
        '''called rapidly by mavproxy'''
        now = time.time()
        time_delta = now - self.last_calc
        if time_delta > 1:
            self.last_calc = now
            self.buckets.append(self.counts)
            self.counts = {}
            if len(self.buckets) > self.max_buckets:
                self.buckets = self.buckets[-self.max_buckets:]
called rapidly by mavproxy