Make live data loop more rugged

It was possible to get into a state where every pointer change was being
detected late and it never woke up early enough to set the station clock
and start logging data. This change should stop that happening.

Signed-off-by: Jim Easterbrook <jim@jim-easterbrook.me.uk>

src/pywws/WeatherStation.py

@@ -1,6 +1,6 @@
 # pywws - Python software for USB Wireless Weather Stations
 # http://github.com/jim-easterbrook/pywws
-# Copyright (C) 2008-15  Jim Easterbrook  jim@jim-easterbrook.me.uk
+# Copyright (C) 2008-15  pywws contributors
 
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -411,6 +411,7 @@ def live_data(self, logged_only=False):
         # due. (During initialisation we get data every half second
         # anyway.)
         read_period = self.get_fixed_block(['read_period'])
+        self.logger.debug('read period %d', read_period)
         log_interval = float(read_period * 60)
         live_interval = 48.0
         old_ptr = self.current_pos()
@@ -496,10 +497,18 @@ def live_data(self, logged_only=False):
                 if ptr_time - last_ptr_time < self.margin:
                     # pointer has just changed, so definitely at a logging time
                     self._station_clock.set_clock(ptr_time)
-                elif next_log and ptr_time < next_log - self.margin:
-                    self.logger.warning(
-                        'live_data lost log sync %g', ptr_time - next_log)
-                    self._station_clock.invalidate()
+                elif next_log:
+                    if ptr_time < next_log - self.margin:
+                        self.logger.warning(
+                            'live_data lost log sync %g', ptr_time - next_log)
+                        self._station_clock.invalidate()
+                else:
+                    self.logger.warning('missed ptr change time')
+                    last_log -= live_interval
+                if read_period > new_data['delay']:
+                    read_period = new_data['delay']
+                    self.logger.warning('reset read period %d', read_period)
+                    log_interval = float(read_period * 60)
                 next_log = self._station_clock.nearest(ptr_time)
                 if next_log:
                     result = dict(new_data)

src/pywws/__init__.py

@@ -1,3 +1,3 @@
-__version__ = '15.07.0.dev1304'
-_release = '1304'
-_commit = 'c851b94'
+__version__ = '15.07.0.dev1305'
+_release = '1305'
+_commit = '328747c'