Merge pull request #399 from davidsaada/david_nvstore

Add documentation for NVStore

Author: Amanda Butler

docs/reference/api/storage/NVStore.md

@@ -0,0 +1,15 @@
+## NVStore
+
+NVStore is a lightweight module that stores data by keys in the internal flash for security purposes. For each item key, the NVStore module provides the ability to set the item data or get it. Newly added values are added to the end of the existing data, superseding the previous value that was there for the same key. The NVStore module ensures that power failures don't harm existing data during any operation.
+
+### Flash structure
+
+NVStore uses two Flash areas, active and nonactive. Each area must consist of at least one erasable unit (sector). Data is written to the active area until it becomes full. When it does, garbage collection is invoked. This compacts items from the active area to the nonactive one and switches activity between areas. Each item is kept in an entry containing a header and data, where the header holds the item key, size and CRC.
+
+### NVStore class reference
+
+[![View code](https://www.mbed.com/embed/?type=library)](http://os-doc-builder.test.mbed.com/docs/development/mbed-os-api-doxy/nvstore_8h_source.html)
+
+### NVStore example
+
+[![View code](https://www.mbed.com/embed/?url=http://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-nvstore)](https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-nvstore/file/0a3e19b12855/main.cpp/)

docs/reference/configuration/Storage.md

@@ -95,4 +95,36 @@ Name: littlefs.enable_error
     Defined by: library:littlefs
     Macro name: MBED_LFS_ENABLE_ERROR
     Value: null (set by library:littlefs)
+
+Name: nvstore.max_keys
+    Description:
+        Maximal number of allowed NVStore keys.
+    Defined by: library:nvstore
+    Macro name: NVSTORE_MAX_KEYS
+    Value: 16 (set by library:nvstore)
+Name: nvstore.area_1_address
+    Description:
+        Address of the first NVStore area in flash.
+    Defined by: library:nvstore
+    Macro name: NVSTORE_AREA_1_ADDRESS
+    Value: null (set by library:nvstore)
+Name: nvstore.area_1_size
+    Description:
+        Size of the first NVStore area in flash.
+    Defined by: library:nvstore
+    Macro name: NVSTORE_AREA_1_SIZE
+    Value: null (set by library:nvstore)
+Name: nvstore.area_2_address
+    Description:
+        Address of the second NVStore area in flash.
+    Defined by: library:nvstore
+    Macro name: NVSTORE_AREA_2_ADDRESS
+    Value: null (set by library:nvstore)
+Name: nvstore.area_2_size
+    Description:
+        Size of the second NVStore area in flash.
+    Defined by: library:nvstore
+    Macro name: NVSTORE_AREA_2_SIZE
+    Value: null (set by library:nvstore)
+
 ```