EpicsMotor support for enable/disable

[prjemian]

As requested by email:

Say I define a “Epicsmotor” in bluesky…

samx = EpicsMotor(“6bma:m34”, name=”samx”)

Is there an easy way to know the status of motor ( “enabled” or “disabled”?) and switch the status ? ….

The PV to reflect the status is “6bma:m34_able”, and I can do it by modifying it directly with caput()…

[prjemian]

@cpchuang: Your question is now an issue for apstools

[prjemian]

At its simplest, a subclass of ophyd.EpicsMotor that provides access to motor enable/disable might look like this example:

In [20]: class MyMotor(EpicsMotor):
    ...:     enable_disable = Component(EpicsSignal, "_able")
    ...:
    ...: otzm2 = MyMotor("otz:m2", name="otzm2")
    ...:

In [21]: otzm2.read()
Out[21]:
OrderedDict([('otzm2', {'value': 1.0, 'timestamp': 1558536998.666}),
             ('otzm2_user_setpoint',
              {'value': 1.0, 'timestamp': 1558536998.666}),
             ('otzm2_enable_disable',
              {'value': 0, 'timestamp': 1558536305.847636})])

Since there are many such fields in the EPICS motor record which are not provided in ophyd.EpicsMotor, I prefer to take the approach of defining a "mixin" class so that one or more mixins can augment the capabilities of ophyd.EpicsMotor. Here is my mixin class for enable/disable:

In [24]:
    ...: MOTOR_ENABLE = 0
    ...: MOTOR_DISABLE = 1
    ...:
    ...: class EnableEpicsMotorMixin(APS_devices.DeviceMixinBase):
    ...:     """
    ...:     mixin providing access to motor enable/disable
    ...:     """
    ...:     enable_disable = Component(EpicsSignal, "_able")
    ...:
    ...:     @property
    ...:     def enabled(self):
    ...:         return self.enable_disable.value in (MOTOR_ENABLE, "Enabled")
    ...:
    ...:     def enable_motor(self):
    ...:         """BLOCKING call to enable motor axis"""
    ...:         self.enable_disable.put(MOTOR_ENABLE)
    ...:
    ...:     def disable_motor(self):
    ...:         """BLOCKING call to disable motor axis"""
    ...:         self.enable_disable.put(MOTOR_DISABLE)
    ...:
    ...: class MyMotor(EnableEpicsMotorMixin, EpicsMotor):
    ...:     """
    ...:     EpicsMotor with support for enable/disable
    ...:     """
    ...:
    ...: otzm2 = MyMotor("otz:m2", name="otzm2")
    ...:

In [25]: otzm2.read()
Out[25]:
OrderedDict([('otzm2', {'value': 1.0, 'timestamp': 1558536998.666}),
             ('otzm2_user_setpoint',
              {'value': 1.0, 'timestamp': 1558536998.666}),
             ('otzm2_enable_disable',
              {'value': 0, 'timestamp': 1558536305.847636})])

In [26]: otzm2.enabled
Out[26]: True

In [27]: otzm2.disable_motor()

In [28]: otzm2.enabled
Out[28]: False

In [29]: otzm2.enable_motor()

In [30]: otzm2.enabled
Out[30]: True

[prjemian]

Following the lead of ophyd.EpicsMotor, add a flag that removes this new signal from the values returned by MOTOR.read():

    enable_disable = Component(EpicsSignal, "_able", kind='omitted')