Work with Devices

Note

Assuming you’ve followed the quickstart guide or otherwise got an IPython terminal to control a test rig…

There are objects provided that represent the hardware devices on the test rig, for example, the motors. The devices exist in a tree-like heirachy, so you can drill down into individual motors.

In [1]: sample_stage
Out[1]: SampleStage(prefix='BL49P-MO-MAP-01:STAGE:', name='sample_stage', read_attrs=['x', 'x.user_readback', 'x.user_setpoint', 'theta', 'theta.user_readback', 'theta.user_setpoint'], configuration_attrs=['x', 'x.user_offset', 'x.user_offset_dir', 'x.velocity', 'x.acceleration', 'x.motor_egu', 'theta', 'theta.user_offset', 'theta.user_offset_dir', 'theta.velocity', 'theta.acceleration', 'theta.motor_egu'])

In [2]: sample_stage.theta
Out[2]: EpicsMotor(prefix='BL49P-MO-MAP-01:STAGE:A', name='sample_stage_theta', parent='sample_stage', settle_time=0.0, timeout=None, read_attrs=['user_readback', 'user_setpoint'], configuration_attrs=['user_offset', 'user_offset_dir', 'velocity', 'acceleration', 'motor_egu'])

You can call describe() on an Ophyd object to see what information can be recorded about it as beamline data.

In [3]: sample_stage.theta.describe()
Out[3]:
OrderedDict([('sample_stage_theta',
            {'source': 'PV:BL49P-MO-MAP-01:STAGE:A.RBV',
            'dtype': 'number',
            'shape': [],
            'units': 'mm',
            'lower_ctrl_limit': 0.0,
            'upper_ctrl_limit': 0.0,
            'precision': 3}),
            ('sample_stage_theta_user_setpoint',
            {'source': 'PV:BL49P-MO-MAP-01:STAGE:A.VAL',
            'dtype': 'number',
            'shape': [],
            'units': 'mm',
            'lower_ctrl_limit': 0.0,
            'upper_ctrl_limit': 0.0,
            'precision': 3})])

There is a simple Bluesky plan for moving the motor:

In [4]: RE(bps.mv(sample_stage.theta, 0))
Out[4]: ()

In [5]: RE(bps.mv(sample_stage.theta, 360*5))
Out[5]: ()

Note

RE refers to the Bluesky RunEngine, which executes plans and does the actual talking to hardware.

While moving the motors, you can open the EDM synoptic and observe their behavoir in EPICS too (this is particularly useful for debugging). All 4 test rigs can be found in the Diamond launcher under Beamlines -> Lab IOCs.

mv() can move multiple motors simultaneously too:

In [6]: RE(bps.mv(sample_stage.theta, -360*5, sample_stage.x, 0))
Out[6]: ()