Class AmplitudeScannerShutter

examples/backend_frontend/myapps.py:97–148

A complex application that requires a function generator, an oscilloscope and a shutter. We could subclass AmplitudeScanner, but we have chosen to embed it instead.

class AmplitudeScannerShutter(Backend):
    """A complex application that requires a function generator, an
    oscilloscope and a shutter.

    We could subclass AmplitudeScanner, but we have chosen to embed it instead.
    """

    # Enumerate drivers required by the backend marking them with InstrumentSlot
    osci = InstrumentSlot
    fungen = InstrumentSlot
    shutter = InstrumentSlot

    # Embedded apps (Notice we embed the backend, not the Frontend)
    scanner = AmplitudeScanner

    # This signal will be emited when new data is available.
    new_data = QtCore.Signal(object, object)

    def scan_amplitude(self, amplitudes):
        """Open the shutter an then for each amplitude:
        - scan the amplitude of the function generator.
        - sleeps .3 seconds.
        - measures the trace of the oscilloscope.
        - yields amplitude, data for each amplitude.

        Finally, close the shutter.

        :param amplitudes: iterable of amplitudes.
        """
        self.shutter.opened = True

        # We use the embedded app to perform the actual operation.
        # Notice that we have not explicitly instantiated the AmplitudeScanner
        # nor provided the instruments. Lantz has done this in the back
        # connecting InstrumentsSlots by name.
        # i.e. self.osci is self.scanner.osci
        for amplitude, data in self.scanner.scan_amplitude(amplitudes):
            self.new_data.emit(amplitude, data)
            yield amplitude, data

        self.shutter.opened = False

    def _scan_amplitude(self, amplitudes):
        """Because scan_amplitude is a generator, this helper functions is used
        to iterate over all the items.
        """
        return list(self.scan_amplitude(amplitudes))

    def default_scan(self):
        """A linear scan from 1 to 19 Volts.
        """
        return list(self.scan_amplitude(Q_(list(range(1, 20)), 'volt')))


class AmplitudeScannerShutterUi(Frontend):