Adding Continuous Acquisition Multiple Sample External Trigger example in NI-DMM

CHANGELOG.md

@@ -800,6 +800,7 @@
 #### [nidmm] Unreleased
 - Added
   - Added the `nidmm_measure_ac_volts.py` example.
+  - Added the `nidmm_cont_acq_multiple_samples_ext_trig.py` example.
   - Added the `nidmm_diode_test.py` example.
   - Added the `nidmm_measure_capacitance.py` example.
   - Added the `nidmm_measure_temperature_rtd.py` example.

docs/nidmm/examples.rst

@@ -3,6 +3,15 @@ Examples
 
 `You can download all nidmm examples for latest version here <https://github.com/ni/nimi-python/releases/download/nidmm-1.5.0/nidmm_examples.zip>`_
 
+nidmm_cont_acq_multiple_samples_ext_trig.py
+-------------------------------------------
+
+.. literalinclude:: ../../src/nidmm/examples/nidmm_cont_acq_multiple_samples_ext_trig.py
+   :language: python
+   :linenos:
+   :encoding: utf8
+   :caption: `(nidmm_cont_acq_multiple_samples_ext_trig.py) <https://github.com/ni/nimi-python/blob/master/src/nidmm/examples/nidmm_cont_acq_multiple_samples_ext_trig.py>`_
+
 nidmm_diode_test.py
 -------------------
 

src/nidmm/examples/nidmm_cont_acq_multiple_samples_ext_trig.py

@@ -0,0 +1,110 @@
+#!/usr/bin/python
+
+import argparse
+import collections
+import nidmm
+import pytest
+import sys
+
+
+# Number of most recent measurements kept on the chart
+CHART_HISTORY_SIZE = 250
+
+# Maximum points a single fetch_multi_point call can return in a continuous acquisition, per the array_size documentation
+MAX_SAMPLES_PER_FETCH = 100000
+
+
+def _create_chart(plt):
+    figure, axes = plt.subplots()
+    (line,) = axes.plot([])
+    axes.set_title('Measurements')
+    axes.set_xlabel('Samples')
+    axes.set_ylabel('Measured value')
+    axes.grid(True)
+    return figure, axes, line
+
+
+def _update_chart(plt, axes, line, measurements, new_samples, samples_fetched):
+    measurements.extend(new_samples)
+    first_sample = samples_fetched - len(measurements)
+    line.set_data(range(first_sample, samples_fetched), measurements)
+    axes.relim()
+    axes.autoscale_view()
+    plt.pause(0.001)
+
+
+def example(resource_name, options, function, measurement_range, digits, trigger_source, total_samples):
+    import matplotlib.pyplot as plt
+
+    with nidmm.Session(resource_name=resource_name, reset_device=True, options=options) as session:
+        session.configure_measurement_digits(measurement_function=nidmm.Function[function], range=measurement_range, resolution_digits=digits)
+        # Trigger slopes use driver defaults because the public API has no slope configuration (#875).
+        try:
+            session.configure_trigger(trigger_source=nidmm.TriggerSource[trigger_source])
+            # The sample trigger uses the same source as the trigger; a sample_count of 0 configures a continuous acquisition
+            session.configure_multi_point(trigger_count=1, sample_count=0, sample_trigger=nidmm.SampleTrigger[trigger_source])
+        except nidmm.errors.DriverError as e:
+            # Not every device supports every trigger source (for example, NI 408x devices have no external trigger)
+            sys.exit('The device does not support trigger source {}.\n{}'.format(trigger_source, e.description))
+
+        figure, axes, line = _create_chart(plt)
+        measurements = collections.deque(maxlen=CHART_HISTORY_SIZE)
+
+        samples_fetched = 0
+        try:
+            with session.initiate():
+                # A total_samples of None runs until the chart window is closed or Ctrl+C is pressed
+                while plt.fignum_exists(figure.number) and (
+                    total_samples is None or samples_fetched < total_samples
+                ):
+                    backlog, _ = session.read_status()
+                    if backlog > 0:
+                        new_samples = session.fetch_multi_point(array_size=min(backlog, MAX_SAMPLES_PER_FETCH))
+                        samples_fetched += len(new_samples)
+                        _update_chart(plt, axes, line, measurements, new_samples, samples_fetched)
+                    else:
+                        # Process chart events while waiting for the next trigger.
+                        plt.pause(0.001)
+
+            # The acquisition has stopped; keep the final chart on screen until its window is closed
+            if total_samples is not None and plt.fignum_exists(figure.number):
+                plt.show()
+        except KeyboardInterrupt:
+            pass
+        finally:
+            plt.close(figure)
+
+
+def _main(argsv):
+    parser = argparse.ArgumentParser(description='Continuously acquires measurements on each trigger and displays them on a chart using the NI-DMM API.', formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+    parser.add_argument('-n', '--resource-name', default='PXI1Slot2', help='Contains the resource_name of the device to initialize.')
+    parser.add_argument('-f', '--function', default='DC_VOLTS', choices=nidmm.Function.__members__.keys(), type=str.upper, help='Specifies the measurement_function used to acquire the measurement.')
+    parser.add_argument('-r', '--range', default=10, type=float, help='Specifies the range for the function specified in the Measurement_Function parameter.')
+    parser.add_argument('-d', '--digits', default=5.5, type=float, help='Specifies the resolution of the measurement in digits.')
+    parser.add_argument('-t', '--trigger-source', default='EXTERNAL', choices=nidmm.TriggerSource.__members__.keys(), type=str.upper, help='Specifies the trigger source that initiates the acquisition.')
+    parser.add_argument('--total-samples', default=None, type=int, help='Specifies the maximum number of samples to acquire; omit to run until the chart closes or Ctrl+C is pressed.')
+    parser.add_argument('-op', '--option-string', default='', type=str, help='Sets the initial value of certain attributes for the session.')
+    args = parser.parse_args(argsv)
+    example(args.resource_name, args.option_string, args.function, args.range, args.digits, args.trigger_source, args.total_samples)
+
+
+def main():
+    _main(sys.argv[1:])
+
+
+def test_example():
+    plt = pytest.importorskip('matplotlib.pyplot')
+    plt.switch_backend('Agg')  # Avoid opening a chart window during the test
+    options = {'simulate': True, 'driver_setup': {'Model': '4082', 'BoardType': 'PXIe', }, }
+    example('PXI1Slot2', options, 'DC_VOLTS', 10, 5.5, 'IMMEDIATE', 10)
+
+
+def test_main():
+    plt = pytest.importorskip('matplotlib.pyplot')
+    plt.switch_backend('Agg')  # Avoid opening a chart window during the test
+    cmd_line = ['--option-string', 'Simulate=1, DriverSetup=Model:4082; BoardType:PXIe', '--trigger-source', 'IMMEDIATE', '--total-samples', '10', ]
+    _main(cmd_line)
+
+
+if __name__ == '__main__':
+    main()