3 files changed, 52 insertions, 14 deletions
diff --git a/docs/library/index.rst b/docs/library/index.rst
index 8a93b8c4d0..eb6a466255 100644
--- a/docs/library/index.rst
+++ b/docs/library/index.rst
@@ -4,6 +4,11 @@ Micro Python libraries
 Python standard libraries
 -------------------------
 
+The following standard Python libraries are built in to Micro Python.
+
+For additional libraries, please download them from the `micropython-lib repository
+<https://github.com/micropython/micropython-lib>`_.
+
 .. toctree::
    :maxdepth: 1
 
@@ -12,11 +17,23 @@ Python standard libraries
    math.rst
    os.rst
    select.rst
+   struct.rst
    sys.rst
    time.rst
 
-Micro Python reduced libraries
-------------------------------
+Python micro-libraries
+----------------------
+
+The following standard Python libraries have been "micro-ified" to fit in with
+the philosophy of Micro Python.  They provide the core functionality of that
+module and are intended to be a drop-in replacement for the standard Python
+library.
+
+The modules are available by their u-name, and also by their non-u-name.  The
+non-u-name can be overridden by a file of that name in your package path.
+For example, ``import json`` will first search for a file ``json.py`` or
+directory ``json`` and load that package if it is found.  If nothing is found,
+it will fallback to loading the built-in ``ujson`` module.
 
 .. toctree::
    :maxdepth: 1
@@ -28,6 +45,8 @@ Micro Python reduced libraries
 Libraries specific to the pyboard
 ---------------------------------
 
+The following libraries are specific to the pyboard.
+
 .. toctree::
    :maxdepth: 2
 
diff --git a/docs/library/pyb.SPI.rst b/docs/library/pyb.SPI.rst
index 7ad3a90e2d..7b765e6b06 100644
--- a/docs/library/pyb.SPI.rst
+++ b/docs/library/pyb.SPI.rst
@@ -93,18 +93,12 @@ Methods
 Constants
 ---------
 
-.. data:: LSB
+.. data:: SPI.MASTER
+.. data:: SPI.SLAVE
 
-   set the first bit to LSB
+   for initialising the SPI bus to master or slave mode
 
-.. data:: MASTER
+.. data:: SPI.LSB
+.. data:: SPI.MSB
 
-   for initialising the bus to master mode
-
-.. data:: MSB
-
-   set the first bit to MSB
-
-.. data:: SLAVE
-
-   for initialising the bus to slave mode
+   set the first bit to be the least or most significant bit
diff --git a/docs/library/struct.rst b/docs/library/struct.rst
new file mode 100644
index 0000000000..71ee5c9b70
--- /dev/null
+++ b/docs/library/struct.rst
@@ -0,0 +1,25 @@
+:mod:`struct` -- pack and unpack primitive data types
+=====================================================
+
+.. module:: struct
+   :synopsis: pack and unpack primitive data types
+
+See `Python struct <https://docs.python.org/3/library/struct.html>`_ for more
+information.
+
+Functions
+---------
+
+.. function:: calcsize(fmt)
+
+   Return the number of bytes needed to store the given ``fmt``.
+
+.. function:: pack(fmt, v1, v2, ...)
+
+   Pack the values ``v1``, ``v2``, ... according to the format string ``fmt``.
+   The return value is a bytes object encoding the values.
+
+.. function:: unpack(fmt, data)
+
+   Unpack from the ``data`` according to the format string ``fmt``.
+   The return value is a tuple of the unpacked values.