Create a common base for attenuator

src/dodal/beamlines/i24.py

@@ -1,5 +1,6 @@
 from dodal.common.beamlines.beamline_utils import BL, device_instantiation
 from dodal.common.beamlines.beamline_utils import set_beamline as set_utils_beamline
+from dodal.devices.attenuator_base import AttenuatorBase
 from dodal.devices.detector import DetectorParams
 from dodal.devices.eiger import EigerDetector
 from dodal.devices.hutch_shutter import HutchShutter
@@ -29,6 +30,22 @@
 set_utils_beamline(BL)
 
 
+def attenuator(
+    wait_for_connection: bool = True, fake_with_ophyd_sim: bool = False
+) -> AttenuatorBase:
+    """Get a basic (temporarily without filter wheels) attenuator device for i24,
+    instantiate it if it hasn't already been. If this is called when already \
+    instantiated in i24, it will return the existing object."""
+    # For filter wheels see https://github.com/DiamondLightSource/dodal/issues/927
+    return device_instantiation(
+        AttenuatorBase,
+        "attenuator",
+        "-OP-ATTN-01:",
+        wait_for_connection,
+        fake_with_ophyd_sim,
+    )
+
+
 def aperture(
     wait_for_connection: bool = True, fake_with_ophyd_sim: bool = False
 ) -> Aperture:

src/dodal/devices/attenuator.py

@@ -6,15 +6,15 @@
     AsyncStatus,
     DeviceVector,
     SignalR,
-    StandardReadable,
     wait_for_value,
 )
-from ophyd_async.epics.core import epics_signal_r, epics_signal_rw, epics_signal_x
+from ophyd_async.epics.core import epics_signal_r, epics_signal_x
 
+from dodal.devices.attenuator_base import AttenuatorBase
 from dodal.log import LOGGER
 
 
-class Attenuator(StandardReadable, Movable):
+class Attenuator(AttenuatorBase, Movable):
     """The attenuator will insert filters into the beam to reduce its transmission.
 
     This device should be set with:
@@ -38,14 +38,9 @@ def __init__(self, prefix: str, name: str = ""):
             }
         )
 
-        self._desired_transmission = epics_signal_rw(float, prefix + "T2A:SETVAL1")
-        self._use_current_energy = epics_signal_x(prefix + "E2WL:USECURRENTENERGY.PROC")
         self._change = epics_signal_x(prefix + "FANOUT")
 
-        with self.add_children_as_readables():
-            self.actual_transmission = epics_signal_r(float, prefix + "MATCH")
-
-        super().__init__(name)
+        super().__init__(prefix, name)
 
     @AsyncStatus.wrap
     async def set(self, value: float):

src/dodal/devices/attenuator_base.py

@@ -0,0 +1,22 @@
+from ophyd_async.core import StandardReadable
+from ophyd_async.epics.core import epics_signal_r, epics_signal_rw, epics_signal_x
+
+# This will need a set
+# See https://github.com/DiamondLightSource/dodal/issues/928
+
+
+class AttenuatorBase(StandardReadable):
+    """An attenuator base class with a minimum set of common PVs to phase1 beamlines.
+
+    The desired transmission value is fractional (i.e 0-1) instead of a percentage, \
+    and when read from the device the actual_transmission will also return a fraction.
+    """
+
+    def __init__(self, prefix: str, name: str = "") -> None:
+        self._desired_transmission = epics_signal_rw(float, prefix + "T2A:SETVAL1")
+        self._use_current_energy = epics_signal_x(prefix + "E2WL:USECURRENTENERGY.PROC")
+
+        with self.add_children_as_readables():
+            self.actual_transmission = epics_signal_r(float, prefix + "MATCH")
+
+        super().__init__(name)