Ensure motors can be stopped (#688)

src/ophyd_async/epics/motor.py

@@ -20,7 +20,7 @@
     observe_value,
 )
 from ophyd_async.core import StandardReadableFormat as Format
-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_rw, epics_signal_w
 
 
 class MotorLimitsException(Exception):
@@ -76,7 +76,10 @@ def __init__(self, prefix: str, name="") -> None:
         self.low_limit_travel = epics_signal_rw(float, prefix + ".LLM")
         self.high_limit_travel = epics_signal_rw(float, prefix + ".HLM")
 
-        self.motor_stop = epics_signal_x(prefix + ".STOP")
+        # Note:cannot use epics_signal_x here, as the motor record specifies that
+        # we must write 1 to stop the motor. Simply processing the record is not
+        # sufficient.
+        self.motor_stop = epics_signal_w(int, prefix + ".STOP")
         # Whether set() should complete successfully or not
         self._set_success = True
 
@@ -178,7 +181,7 @@ async def stop(self, success=False):
         self._set_success = success
         # Put with completion will never complete as we are waiting for completion on
         # the move above, so need to pass wait=False
-        await self.motor_stop.trigger(wait=False)
+        await self.motor_stop.set(1, wait=False)
 
     async def _prepare_velocity(
         self, start_position: float, end_position: float, time_for_move: float

tests/epics/test_motor.py

@@ -10,6 +10,7 @@
     AsyncStatus,
     DeviceCollector,
     callback_on_mock_put,
+    get_mock_put,
     mock_puts_blocked,
     observe_value,
     set_mock_put_proceeds,
@@ -154,6 +155,11 @@ async def test_motor_moving_stopped(sim_motor: motor.Motor):
     await asyncio.sleep(0.2)
     assert not s.done
     await sim_motor.stop()
+
+    # Note: needs to explicitly be called with 1, not just processed.
+    # See https://epics.anl.gov/bcda/synApps/motor/motorRecord.html#Fields_command
+    get_mock_put(sim_motor.motor_stop).assert_called_once_with(1, wait=False)
+
     set_mock_put_proceeds(sim_motor.user_setpoint, True)
     await wait_for_pending_wakeups()
     assert s.done