refactor(ddg1): Use mcs acquiring status to resolve trigger of DDG1

csaxs_bec/devices/epics/delay_generator_csaxs/ddg_1.py

@@ -135,6 +135,7 @@ class DDG1(PSIDeviceBase, DelayGeneratorCSAXS):
 
     USER_ACCESS = ["keep_shutter_open_during_scan", "set_trigger"]
 
+    # TODO Consider using the 'fsh' device instead.
     fast_shutter_readback = Cpt(
         EpicsSignalRO,
         read_pv="X12SA-ES1-TTL:INP_01",
@@ -513,14 +514,14 @@ class DDG1(PSIDeviceBase, DelayGeneratorCSAXS):
         """
         self._stop_polling()
         self._poll_thread_poll_loop_done.wait(timeout=1)
-        time.sleep(0.02)
-        # TODO This may move to scan modifiers
+
+        # NOTE If the trigger source is not SINGLE_SHOT, the DDG is triggered by an external source
+        # thus we can not expect that trigger signals are meant to be awaited for. In this case,
+        # we can directly return.
         if self.trigger_source.get() != TRIGGERSOURCE.SINGLE_SHOT.value:
             status = StatusBase(obj=self)
             status.set_finished()
             return status
-        # NOTE: This sleep is important to ensure that the HW is ready to process new commands.
-        # It has been empirically determined after long testing that this improves stability.
 
         # NOTE If the MCS card is present in the current session of BEC,
         # we prepare the card for the next trigger. The procedure is implemented
@@ -536,11 +537,12 @@ class DDG1(PSIDeviceBase, DelayGeneratorCSAXS):
             # be investigated why the EPICS interface is slow to respond.
             status_mcs.wait(timeout=3)
 
-        if self.fast_shutter_control.get() == 0:
-            # Shutter is not kept open, we can rely on the shutter readback signal
-            status = TransitionStatus(
-                self.fast_shutter_readback, [1, 0]
-            )  # Wait for shutter to transition from open (1) to close (0)
+        # NOTE If the MCS card is present, we may also use its signal wait for the burst cycle to finish.
+        # This is True for any non-fly scans, as for fly scans the MCS card will not receive the additional
+        # trigger pulse from the ef delay pair, check on_stage.
+        if mcs is not None and mcs.enabled and self.scan_info.msg.scan_type != "fly":
+            # We can use the acquiring signal of the MCS card to check if the burst cycle is finished.
+            status = TransitionStatus(mcs.acquiring, [ACQUIRING.ACQUIRING, ACQUIRING.DONE])
         else:
             # NOTE This sleep is needed for 20ms to make sure that the HW of the DDG is
             # again ready to process new commands. It was transferred from just after the