Add use cases

Author: coretl

docs/explanations/use-cases.rst

@@ -0,0 +1,55 @@
+Why use pythonIOC?
+==================
+
+EPICS IOCs are flexible and modular, why do we need to wrap it in Python? This
+page attempts to answer that question and list a few good use-cases for it.
+
+Calculating PVs from other values
+---------------------------------
+
+Some use cases require PVs to be calculated from multiple sources. This is
+possible in EPICS records with ``calc`` or ``aSub`` records, but pythonIoc
+allows you to write this as:
+
+.. code-block::
+
+    import numpy as np
+    from cothread.catools import caget, camonitor
+    from softioc import builder
+
+    # The PVs we want to average and their initial values
+    PVs = [f"DEVICE{i}:CURRENT" for i in range(100)]
+    values = np.array(caget(PVs))
+
+    # The PV we want to serve
+    avg = builder.aOut("AVERAGE:CURRENT", np.mean(values))
+
+    # Make a monitor on the PVs to keep the value up to date
+    def update_avg(value: float, index: int):
+        values[index] = value
+        avg.set(np.mean(values))
+
+    camonitor(PVs, update_avg)
+
+ADD THE CONCENTRATOR USE CASE HERE
+
+Dynamically created PVs
+-----------------------
+
+Other use cases will do something like:
+
+.. code-block::
+
+    connect to device
+    make PVs
+
+ADD THE PANDA USE CASE HERE
+
+Existing Python Support
+-----------------------
+
+It may be that you have specific device support written in Python that you wish
+to expose as PVs.
+
+NEED A GOOD EXAMPLE HERE
+

docs/explanations/why-use-pythonIoc.rst

@@ -59,7 +59,7 @@ About the documentation
     :name: explanations
     :maxdepth: 1
 
-    explanations/use-cases
+    explanations/why-use-pythonIoc
 
 .. rst-class:: no-margin-after-ul
 

docs/index.rst

@@ -1,6 +1,8 @@
 Creating an IOC
 ===============
 
+THIS NEEDS UPDATING
+
 Using ``pythonSoftIoc``
 -----------------------