Merge pull request #227 from DiamondLightSource/895_hyperion_fgs_dwel…

…l_time

Validate the dwell_time parameter's datatype

src/dodal/devices/fast_grid_scan.py

@@ -61,7 +61,7 @@ class GridScanParams(BaseModel, AbstractExperimentParameterBase):
     x_step_size: float = 0.1
     y_step_size: float = 0.1
     z_step_size: float = 0.1
-    dwell_time_ms: float = 0.1
+    dwell_time_ms: float = 10
     x_start: float = 0.1
     y1_start: float = 0.1
     y2_start: float = 0.1
@@ -91,6 +91,18 @@ def _get_y_axis(cls, y_axis: GridAxis, values: dict[str, Any]) -> GridAxis:
     def _get_z_axis(cls, z_axis: GridAxis, values: dict[str, Any]) -> GridAxis:
         return GridAxis(values["z2_start"], values["z_step_size"], values["z_steps"])
 
+    @validator("dwell_time_ms", always=True, check_fields=True)
+    def non_integer_dwell_time(cls, dwell_time_ms: float) -> float:
+        dwell_time_floor_rounded = np.floor(dwell_time_ms)
+        dwell_time_is_close = np.isclose(
+            dwell_time_ms, dwell_time_floor_rounded, rtol=1e-3
+        )
+        if not dwell_time_is_close:
+            raise ValueError(
+                f"Dwell time of {dwell_time_ms}ms is not an integer value. Fast Grid Scan only accepts integer values"
+            )
+        return dwell_time_ms
+
     def is_valid(self, limits: XYZLimitBundle) -> bool:
         """
         Validates scan parameters

tests/devices/unit_tests/test_gridscan.py

@@ -337,3 +337,33 @@ def test_given_x_y_z_steps_when_full_number_calculated_then_answer_is_as_expecte
     grid_scan_params: GridScanParams,
 ):
     assert grid_scan_params.get_num_images() == 350
+
+
+@pytest.mark.parametrize(
+    "test_dwell_times, expected_dwell_time_is_integer",
+    [
+        (9000, True),
+        (1000, True),
+        (100.1, True),
+        (100.09, True),
+        (150.7, False),
+        (10, True),
+        (99, True),
+        (59, True),
+        (0.4, False),
+        (0.9, False),
+        (0.44, False),
+        (0.99, False),
+        (0.01, False),
+        (0.09, False),
+        (0.001, False),
+        (0.009, False),
+    ],
+)
+def test_non_test_integer_dwell_time(test_dwell_times, expected_dwell_time_is_integer):
+    if expected_dwell_time_is_integer:
+        params = GridScanParams(dwell_time_ms=test_dwell_times)
+        assert params.dwell_time_ms == test_dwell_times
+    else:
+        with pytest.raises(ValueError):
+            GridScanParams(dwell_time_ms=test_dwell_times)