NVS Partition Generator Utility

Introduction

nvs_flash/nvs_partition_generator/nvs_partition_gen.py utility is designed to help create a binary file, compatible with NVS architecture defined in Non-Volatile Storage, 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 firmware 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, base64 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, base64, 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

You can run the utility using below command:

python nvs_partition_gen.py [-h] input output size

Positional arguments:

Arguments | Description
— | —
input | Path to CSV file to parse. Will use stdin if omitted (a sample.csv is provided)
output | Path to output converted binary file. Will use stdout if omitted
size | Size of NVS Partition in KB. E.g. 12KB

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.