Wrote user docs for saving data

docs/user/how-to/capture-hdf.rst

@@ -0,0 +1,38 @@
+
+Capture data
+============
+
+The ``:DATA`` PVs are used to capture data from the panda.
+These can be viewed from the DATA screen.
+
+..  image:: /images/data_bobfile.png
+    :alt: The data screen
+    :align: center
+
+
+* The file directory and name are chosen with ``:DATA:HDFDirectory`` and ``:DATA:HDFFileName``.
+* ``:DATA:NumCapture`` is the number of frames to capture in the file.
+* ``:DATA:NumCaptured`` is the number of frames written to file.
+* ``:DATA:NumReceived`` is the number of frames received from the panda.
+* ``:DATA:FlushPeriod`` is the frequency that the data is flushed into frames in the client.
+* ``:DATA:Capture`` will begin capturing data.
+* ``:DATA:CaptureMode`` is one of the three capture modes listed below.
+
+
+First N mode 
+------------
+
+Begin capturing data and writing it to file as soon as it is received. Stop capturing once ``NumCapture``
+frames have been written or the panda has been disarmed.
+
+
+Last N mode
+-----------
+
+Begin capturing data in a buffer, once capturing has finished write the last ``NumCapture`` frames to disk.
+
+
+Forever mode
+------------
+
+Keep capturing and writing frames. Once the panda has been disarmed wait for it to be armed again and continue writing.

docs/user/index.rst

@@ -26,6 +26,7 @@ side-bar.
             :maxdepth: 1
 
             how-to/run-container
+            how-to/capture-hdf
 
         +++