esp-idf/components/nvs_flash/nvs_partition_generator/README.rst

NVS Partition Generator Utility
===============================

Introduction
------------

:component_file:`nvs_flash/nvs_partition_generator/nvs_partition_gen.py` utility is designed to help create a binary file, compatible with NVS architecture defined in :doc:`Non-Volatile Storage </api-reference/storage/nvs_flash>`, based on user provided key-value pairs in a CSV file.
Utility is ideally suited for generating a binary blob, containing data specific to ODM/OEM, which can be flashed externally at the time of device manufacturing. This helps manufacturers set unique value for various parameters for each device, e.g. serial number, while using same application firmaware for all devices.

CSV file format
---------------

Each row of the .csv file should have 4 parameters, separated by comma. Below is the description of each of these parameters:

Key
	Key of the data. Data can later be accessed from an application via this key.

Type
	Supported values are ``file``, ``data`` and ``namespace``.

Encoding
    Supported values are: ``u8``, ``i8``, ``u16``, ``u32``, ``i32``, ``string``, ``hex2bin`` and ``binary``. This specifies how actual data values are encoded in the resultant binary file. Difference between ``string`` and ``binary`` encoding is that ``string`` data is terminated with a NULL character, whereas ``binary`` data is not.

    .. note:: For ``file`` type, only ``hex2bin``, ``string`` and ``binary`` is supported as of now.

Value
	Data value.

.. note:: Encoding and Value cells for ``namespace`` field type should be empty. Encoding and Value of ``namespace`` is fixed and isn't configurable. Any value in these cells are ignored.

.. note:: First row of the CSV file should always be column header and isn't configurable.

Below is an example dump of such CSV file::

    key,type,encoding,value     <-- column header
    namespace_name,namespace,,  <-- First entry should be of type "namespace"
    key1,data,u8,1
    key2,file,string,/path/to/file

.. note:: Make sure there are no spaces before and after ',' in CSV file.

NVS Entry and Namespace association
-----------------------------------

When a new namespace entry is encountered in the CSV file, each follow-up entries will be part of that namespace, until next namespace entry is found, in which case all the follow-up entries will be part of the new namespace.

.. note:: First entry in a CSV file should always be ``namespace`` entry.

Running the utility
-------------------

A sample CSV file provided with the utility. You can run the utility using below command::

    python nvs_partition_generator.py sample.csv sample.bin

Caveats
-------
-  Utility doesn't check for duplicate keys and will write data pertaining to both keys. User needs to make sure keys are distinct.
-  Once a new page is created, no data will be written in the space left in previous page. Fields in the CSV file need to be ordered in such a way so as to optimize memory.
-  64-bit datatype is not yet supported.