FatFs integration (SDIO backend) (#242)

extras/fatfs/README.md

@@ -0,0 +1,55 @@
+# FatFs - Generic FAT File System Module
+
+Current version: R0.12b
+
+## How to use
+
+Connect your SD card to ESP module
+
+ SD pin |  ESP8266 
+--------|------------
+1. DAT2 |  -
+2. /CS  | Any accessible GPIO (15, 5, 4, 0, 2, 16)
+3. DI   | HMOSI (GPIO13)
+4. VDD  | +3V3
+5. CLK  | HCLK (GPIO14)
+6. VSS  | GND
+7. DO   | HMISO (GPIO12)
+8. RSV  | - 
+
+Add `extras/sdio` and `extras/fatfs` to `EXTRA_COMPONENTS` parameter of your
+makefile, e.g.
+
+```Makefile
+EXTRA_COMPONENTS = extras/sdio extras/fatfs
+```
+
+Use `const char *f_gpio_to_volume(uint8_t gpio)` to get the FatFs volume ID
+based on GPIO which is used for CS pin.
+
+## FatFs configuration
+
+Almost all of the FatFs parameters are configurable in the Makefile of your
+project. See default values and their meaning in `defaults.mk`.
+
+## Original documentation
+
+http://elm-chan.org/fsw/ff/00index_e.html
+
+## License
+
+Copyright (C) 20xx, ChaN, all right reserved.
+
+FatFs module is an open source software. Redistribution and use of FatFs in
+source and binary forms, with or without modification, are permitted provided
+that the following condition is met:
+
+1. Redistributions of source code must retain the above copyright notice,
+   this condition and the following disclaimer.
+
+This software is provided by the copyright holder and contributors "AS IS"
+and any warranties related to this software are DISCLAIMED.
+The copyright owner or contributors be NOT LIABLE for any damages caused
+by use of this software.
+
+