mbed-os-examples / Mbed OS mbed-os-example-mbed5-filesystem

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+# Getting started with the Mbed OS file system
+
+This example demonstrates how to use the Mbed OS file system.
+
+Please install [Mbed CLI](https://os.mbed.com/docs/v5.6/tools/setup.html).
+
+## Hardware requirements
+
+This example uses a block device as storage. This can be either an external
+block device or simulated on a heap block device on boards with enough RAM.
+
+## Usage
+
+#### Import the example
+
+Make sure you have an Mbed development environment set up. [Get started with Mbed OS](https://os.mbed.com/docs/v5.6/tutorials/your-first-program.html)
+to set everything up.
+
+From the command-line, import the example:
+
+```
+mbed import mbed-os-example-filesystem
+cd mbed-os-example-filesystem
+```
+
+#### Compile the example
+
+Invoke `mbed compile`, and specify the name of your platform and your favorite
+toolchain (`GCC_ARM`, `ARM`, `IAR`). For example, for the ARM Compiler 5:
+
+```
+mbed compile -m K64F -t ARM
+```
+
+Your PC may take a few minutes to compile your code. At the end, you see the
+following result:
+
+```
+[snip]
++--------------------------+-------+-------+-------+
+| Module                   | .text | .data |  .bss |
++--------------------------+-------+-------+-------+
+| Fill                     |   164 |     0 |  2136 |
+| Misc                     | 54505 |  2556 |   754 |
+| drivers                  |   640 |     0 |    32 |
+| features/filesystem      | 15793 |     0 |   550 |
+| features/storage         |    42 |     0 |   184 |
+| hal                      |   418 |     0 |     8 |
+| platform                 |  2355 |    20 |   582 |
+| rtos                     |   135 |     4 |     4 |
+| rtos/rtx                 |  5861 |    20 |  6870 |
+| targets/TARGET_Freescale |  8382 |    12 |   384 |
+| Subtotals                | 88295 |  2612 | 11504 |
++--------------------------+-------+-------+-------+
+Allocated Heap: 24576 bytes
+Allocated Stack: unknown
+Total Static RAM memory (data + bss): 14116 bytes
+Total RAM memory (data + bss + heap + stack): 38692 bytes
+Total Flash memory (text + data + misc): 91947 bytes
+
+Image: ./BUILD/K64F/ARM/mbed-os-example-filesystem.bin
+```
+
+#### Run the example
+
+1. Connect your Mbed Enabled device to the computer over USB.
+1. Copy the binary file to the Mbed Enabled device.
+1. Press the reset button to start the program.
+1. Open the UART of the board in your favorite UART viewing program. For
+   example, `screen /dev/ttyACM0`.
+   
+**Note:** The default serial port baud rate is 9600 bit/s.
+
+Expected output:
+
+```
+--- Mbed OS filesystem example ---
+Mounting the filesystem... Fail :(
+No filesystem found, formatting... OK
+Opening "/fs/numbers.txt"... Fail :(
+No file found, creating a new file... OK
+Writing numbers (10/10)... OK
+Seeking file... OK
+Incrementing numbers (10/10)... OK
+Closing "/fs/numbers.txt"... OK
+Opening the root directory... OK
+root directory:
+    .
+    ..
+    numbers.txt
+Closing the root directory... OK
+Opening "/fs/numbers.txt"...OK
+numbers:
+    1
+    2
+    3
+    4
+    5
+    6
+    7
+    8
+    9
+    10
+Closing "/fs/numbers.txt"... OK
+Unmounting... OK
+Mbed OS filesystem example done!
+```
+
+You can also reset the board to see the data persist across boots. Each boot
+increments the numbers stored on disk:
+
+```
+--- Mbed OS filesystem example ---
+Mounting the filesystem... OK
+Opening "/fs/numbers.txt"... OK
+Incrementing numbers (10/10)... OK
+Closing "/fs/numbers.txt"... OK
+Opening the root directory... OK
+root directory:
+    .
+    ..
+    numbers.txt
+Closing the root directory... OK
+Opening "/fs/numbers.txt"...OK
+numbers:
+    2
+    3
+    4
+    5
+    6
+    7
+    8
+    9
+    10
+    11
+Closing "/fs/numbers.txt"... OK
+Unmounting... OK
+Mbed OS filesystem example done!
+```
+
+If you find yourself with a corrupted file system, you can reset the storage
+by pressing BUTTON1:
+
+```
+Initializing the block device... OK
+Erasing the block device... OK
+Deinitializing the block device... OK
+```
+
+Note that if you press the reset button at the wrong time, you may corrupt
+a file system that is not power resilient!
+
+#### Troubleshooting
+
+If you have problems, you can review the [documentation](https://os.mbed.com/docs/latest/tutorials/debugging.html)
+for suggestions on what could be wrong and how to fix it.
+
+## Changing the file system
+
+In Mbed OS, a C++ classes that inherits from the [FileSystem](https://os.mbed.com/docs/v5.6/reference/storage.html#declaring-a-file-system)
+interface represents each file system. You can change the file system in the
+example by changing the class declared in main.cpp.
+
+``` diff
+- LittleFileSystem fs("fs");
++ FATFileSysten fs("fs");
+```
+
+Mbed OS has two options for the file system:
+
+- [**LittleFileSystem**](https://os.mbed.com/docs/v5.6/reference/littlefilesystem.html) -
+  The little file system (LittleFS) is a fail-safe file system we designed
+  for embedded systems, specifically for microcontrollers that use flash
+  storage.
+
+  - **Bounded RAM/ROM** - This file system works with a limited amount of memory.
+    It avoids recursion and limits dynamic memory to configurable
+    buffers.
+  
+  - **Power-loss resilient** - We designed this for operating systems
+    that may have random power failures. It has strong copy-on-write
+    guarantees and keeps storage on disk in a valid state.
+  
+  - **Wear leveling** - Because the most common form of embedded storage is
+    erodible flash memories, this file system provides a form of dynamic wear
+    leveling for systems that cannot fit a full flash translation layer.
+
+- **FATFileSystem** - The FAT file system is a well-known file system that you
+  can find on almost every system, including PCs. The Mbed OS implementation of
+  the FAT file system is based on ChanFS and is optimized for small embedded systems.
+
+  - **Portable** - Almost every operating system supports the FAT file system,
+    which is the most common file system found on portable storage, such as SD
+    cards and flash drives. The FAT file system is the easiest way to support
+    access from a PC.
+
+## Changing the block device
+
+In Mbed OS, a C++ classes that inherits from the [BlockDevice](https://os.mbed.com/docs/v5.6/reference/storage.html#block-devices)
+interface represents each block device. You can change the filesystem in the
+example by changing the class declared in main.cpp.
+
+**Note:** Most block devices require pin assignments. Double check that the
+pins in `driver/mbed_lib.json` are correct.
+
+``` diff
+-SPIFBlockDevice bd(
+-        MBED_CONF_SPIF_DRIVER_SPI_MOSI,
+-        MBED_CONF_SPIF_DRIVER_SPI_MISO,
+-        MBED_CONF_SPIF_DRIVER_SPI_CLK,
+-        MBED_CONF_SPIF_DRIVER_SPI_CS);
++SDBlockDevice bd(
++        MBED_CONF_SD_SPI_MOSI,
++        MBED_CONF_SD_SPI_MISO,
++        MBED_CONF_SD_SPI_CLK,
++        MBED_CONF_SD_SPI_CS);
+```
+
+Mbed OS has several options for the block device:
+
+- **SPIFBlockDevice** - Block device driver for NOR-based SPI flash devices that
+support SFDP. NOR-based SPI flash supports byte-sized read and writes, with an
+erase size of about 4kbytes. An erase sets a block to all 1s, with successive
+writes clearing set bits.
+
+- **DataFlashBlockDevice** - Block device driver for NOR-based SPI flash devices
+that support the DataFlash protocol, such as the Adesto AT45DB series of
+devices. DataFlash is a memory protocol that combines flash with SRAM buffers
+for a programming interface. DataFlash supports byte-sized read and writes, with
+an erase size of around 528 bytes or sometimes 1056 bytes. DataFlash provides
+erase sizes with and extra 16 bytes for error correction codes (ECC), so a flash
+translation layer (FTL) may still present 512 byte erase sizes.
+
+- **SDBlockDevice** - Block device driver for SD cards and eMMC memory chips. SD
+cards or eMMC chips offer a full FTL layer on top of NAND flash. This makes the
+storage well-suited for systems that require a about 1GB of memory.
+Additionally, SD cards are a popular form of portable storage. They are useful
+if you want to store data that you can access from a PC.
+
+- [**HeapBlockDevice**](https://os.mbed.com/docs/v5.6/reference/heapblockdevice.html) -
+  Block device that simulates storage in RAM using the heap. Do not use the heap
+  block device for storing data persistently because a power loss causes
+  complete loss of data. Instead, use it fortesting applications when a storage
+  device is not available.
+
+Additionally, Mbed OS contains several utility block devices to give you better
+control over the allocation of storage.
+
+- [**SlicingBlockDevice**](https://os.mbed.com/docs/v5.6/reference/slicingblockdevice.html) -
+  With the slicing block device, you can partition storage into smaller block
+  devices that you can use independently.
+
+- [**ChainingBlockDevice**](https://os.mbed.com/docs/v5.6/reference/chainingblockdevice.html) -
+  With the chaining block device, you can chain multiple block devices together
+  and extend the usable amount of storage.
+
+- [**MBRBlockDevice**](https://os.mbed.com/docs/v5.6/reference/mbrblockdevice.html) -
+  Mbed OS comes with support for storing partitions on disk with a Master Boot
+  Record (MBR). The MBRBlockDevice provides this functionality and supports
+  creating partitions at runtime or using preformatted partitions configured
+  separately from outside the application.
+
+- **ReadOnlyBlockDevice** - With the read-only block device, you can wrap a
+  block device in a read-only layer, ensuring that user of the block device does
+  not modify the storage.
+
+- **ProfilingBlockDevice** - With the profiling block device, you can profile
+  the quantity of erase, program and read operations that are incurred on a
+  block device.
+
+- **ObservingBlockDevice** - The observing block device grants the user the
+  ability to register a callback on block device operations. You can use this to
+  inspect the state of the block device, log different metrics or perform some
+  other operation.
+
+- **ExhaustibleBlockDevice** - Useful for evaluating how file systems respond to
+  wear, the exhaustible block device simulates wear on another form of storage.
+  You can configure it to expire blocks as necessary.
+