text: """
  Copyright (c) 2011, 2012, Regents of the University of California
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions 
  are met:
  
   - Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   - Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the
     distribution.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 
  THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
  OF THE POSSIBILITY OF SUCH DAMAGE.
  """
  """
  @author Stephen Dawson-Haggerty <stevedh@eecs.berkeley.edu>
  """
  from smap.driver import SmapDriver
  from smap.util import periodicSequentialCall
  from smap.contrib import dtutil
  
  from twisted.internet import threads
  
  class Driver(SmapDriver):
      def setup(self, opts):
          self.add_timeseries('/sensor0', 'V')
          self.set_metadata('/sensor0', {
              'Instrument/ModelName' : 'ExampleInstrument'
              })
          self.counter = int(opts.get('StartVal', 0))
          self.rate = float(opts.get('Rate', 1))
  
      def start(self):
          # Call read every 2 seconds
          periodicSequentialCall(self.read).start(self.rate)
  
      def read(self):
          self.add('/sensor0', self.counter)
          self.counter += 1
  
      def load(self, st, et, cache=None):
          d = threads.deferToThread(self.load_data, st, et)
          return d
   
      def load_data(self, st, et):
          st_utc = dtutil.dt2ts(st)
          et_utc = dtutil.dt2ts(et)
          ts = int(st_utc / 120) * 120 # round down to nearest 2-min increment
          while ts <= et_utc:
              self.add('/sensor0', ts, self.counter)
              self.counter += 1
              ts += 120 # 2-min increments
  