Add a dcm device for I24 (#652)

* First dcm commit

* Add basic dcm device for i24

src/dodal/beamlines/i24.py

@@ -5,6 +5,7 @@
 from dodal.devices.hutch_shutter import HutchShutter
 from dodal.devices.i24.aperture import Aperture
 from dodal.devices.i24.beamstop import Beamstop
+from dodal.devices.i24.dcm import DCM
 from dodal.devices.i24.dual_backlight import DualBacklight
 from dodal.devices.i24.I24_detector_motion import DetectorMotion
 from dodal.devices.i24.i24_vgonio import VGonio
@@ -82,6 +83,19 @@ def detector_motion(
     )
 
 
+def dcm(wait_for_connection: bool = True, fake_with_ophyd_sim: bool = False) -> DCM:
+    """Get the i24 DCM device, instantiate it if it hasn't already been.
+    If this is called when already instantiated in i24, it will return the existing object.
+    """
+    return device_instantiation(
+        device_factory=DCM,
+        name="dcm",
+        prefix="",
+        wait=wait_for_connection,
+        fake=fake_with_ophyd_sim,
+    )
+
+
 @skip_device(lambda: BL == "s24")
 def eiger(
     wait_for_connection: bool = True,

src/dodal/devices/i24/dcm.py

@@ -0,0 +1,42 @@
+from ophyd_async.core import StandardReadable
+from ophyd_async.epics.motion import Motor
+from ophyd_async.epics.signal import epics_signal_r
+
+
+class DCM(StandardReadable):
+    """
+    A double crystal monocromator device, used to select the beam energy.
+    """
+
+    def __init__(self, prefix: str, name: str = "") -> None:
+        with self.add_children_as_readables():
+            # Motors
+            self.bragg_in_degrees = Motor(prefix + "-MO-DCM-01:BRAGG")
+            self.x_translation_in_mm = Motor(prefix + "-MO-DCM-01:X")
+            self.offset_in_mm = Motor(prefix + "-MO-DCM-01:OFFSET")
+            self.gap_in_mm = Motor(prefix + "-MO-DCM-01:GAP")
+            self.energy_in_kev = Motor(prefix + "-MO-DCM-01:ENERGY")
+            self.xtal1_roll = Motor(prefix + "-MO-DCM-01:XTAL1:ROLL")
+            self.xtal2_roll = Motor(prefix + "-MO-DCM-01:XTAL2:ROLL")
+            self.xtal2_pitch = Motor(prefix + "-MO-DCM-01:XTAL2:PITCH")
+
+            # Wavelength is calculated in epics from the energy
+            self.wavelength_in_a = epics_signal_r(float, prefix + "-MO-DCM-01:LAMBDA")
+
+            # Temperatures
+            self.xtal1_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-1")
+            self.xtal1_heater_temp = epics_signal_r(
+                float, prefix + "-DI-DCM-01:PT100-2"
+            )
+            self.xtal2_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-4")
+            self.xtal2_heater_temp = epics_signal_r(
+                float, prefix + "-DI-DCM-01:PT100-5"
+            )
+
+            self.roll_plate_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-3")
+            self.pitch_plate_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-6")
+            self.backplate_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-7")
+            self.b1_plate_temp = epics_signal_r(float, prefix + "-DI-DCM-01:PT100-7")
+            self.gap_temp = epics_signal_r(float, prefix + "-DI-DCM-01:TC-1")
+
+        super().__init__(name)