add Capture mode signal to Panda DataBlock (bluesky#604)

src/ophyd_async/fastcs/panda/_block.py

@@ -7,6 +7,12 @@
 from ._table import DatasetTable, SeqTable
 
 
+class CaptureMode(str, Enum):
+    FIRST_N = "FIRST_N"
+    LAST_N = "LAST_N"
+    FOREVER = "FOREVER"
+
+
 class DataBlock(Device):
     # In future we may decide to make hdf_* optional
     hdf_directory: SignalRW[str]
@@ -15,6 +21,7 @@ class DataBlock(Device):
     num_captured: SignalR[int]
     create_directory: SignalRW[int]
     directory_exists: SignalR[bool]
+    capture_mode: SignalRW[CaptureMode]
     capture: SignalRW[bool]
     flush_period: SignalRW[float]
     datasets: SignalR[DatasetTable]

src/ophyd_async/fastcs/panda/_writer.py

@@ -17,7 +17,7 @@
     wait_for_value,
 )
 
-from ._block import DataBlock
+from ._block import CaptureMode, DataBlock
 
 
 class PandaHDFWriter(DetectorWriter):
@@ -58,7 +58,7 @@ async def open(self, multiplier: int = 1) -> dict[str, DataKey]:
             self.panda_data_block.hdf_file_name.set(
                 f"{info.filename}.h5",
             ),
-            self.panda_data_block.num_capture.set(0),
+            self.panda_data_block.capture_mode.set(CaptureMode.FOREVER),
         )
 
         # Make sure that directory exists or has been created.

tests/fastcs/panda/test_panda_utils.py

@@ -71,6 +71,7 @@ def check_equal_with_seq_tables(actual, expected):
     }
     assert parsed_yaml[1] == {
         "data.capture": False,
+        "data.capture_mode": "FIRST_N",
         "data.create_directory": 0,
         "data.flush_period": 0.0,
         "data.hdf_directory": "",