instrument: Add sample_rate_hz attribute for CONTINUOUS instruments

devlib/instrument/__init__.py

@@ -170,6 +170,7 @@ class Instrument(object):
         self.logger = logging.getLogger(self.__class__.__name__)
         self.channels = collections.OrderedDict()
         self.active_channels = []
+        self.sample_rate_hz = None
 
     # channel management
 

devlib/instrument/daq.py

@@ -55,6 +55,7 @@ class DaqInstrument(Instrument):
                                                  resistor_values=resistor_values,
                                                  channel_map=channel_map,
                                                  labels=labels)
+        self.sample_rate_hz = sampling_rate
 
         for label in labels:
             for kind in ['power', 'voltage']:

devlib/instrument/energy_probe.py

@@ -51,6 +51,7 @@ class EnergyProbeInstrument(Instrument):
         self.command = None
         self.raw_output_directory = None
         self.process = None
+        self.sample_rate_hz = 10000 # Determined empirically
 
         for label in self.labels:
             for kind in self.attributes:

devlib/platform/arm.py

@@ -236,6 +236,7 @@ class JunoEnergyInstrument(Instrument):
         for chan in self._channels:
             self.channels[chan.name] = chan
         self.on_target_file = self.target.tempfile('energy', '.csv')
+        self.sample_rate_hz = 10 # DEFAULT_PERIOD is 100[ms] in readenergy.c
         self.command = '{} -o {}'.format(self.binary, self.on_target_file)
         self.command2 = '{}'.format(self.binary)
 

doc/instrumentation.rst

@@ -146,6 +146,12 @@ Instrument
    .. note:: This method is only implemented by :class:`Instrument`\ s that
              support ``CONTINUOUS`` measurment.
 
+.. attribute:: Instrument.sample_rate_hz
+
+   Sample rate of the instrument in Hz. Assumed to be the same for all channels.
+
+   .. note:: This attribute is only provided by :class:`Instrument`\ s that
+             support ``CONTINUOUS`` measurment.
 
 Instrument Channel
 ~~~~~~~~~~~~~~~~~~