Update README.md

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

README.md

@@ -13,11 +13,20 @@ http://www.arduino.cc/en/Reference/SD
 This library is based on FatFs, a generic FAT file system module for small embedded systems.  
 [http://elm-chan.org/fsw/ff](http://elm-chan.org/fsw/ff/00index_e.html)
 
-The FatFs has been ported as Arduino library [here](https://github.com/stm32duino/FatFs). The STM32SD library depends on it.
+The FatFs has been ported as Arduino library [here](https://github.com/stm32duino/FatFs).
+The STM32SD library depends on it.
 
 ## Configuration
+
+### FatFs
 The FatFs has several user defined options, which is specified from within the `ffconf.h` file.
 
 This library provides a default user defined options file named `ffconf_default.h`.
 
-User can provide his own defined options by adding his configuration in a file named `ffconf_custom.h` at sketch level or in variant folder.
+User can provide his own defined options by adding his configuration in a file named
+`ffconf_custom.h` at sketch level or in variant folder.
+
+### SD detect and timeout
+* `SD_DETECT_PIN` pin number can be defined in `variant.h` or using `build_opt.h`.
+
+* `SD_DATATIMEOUT` constant for Read/Write block could be redefined in `variant.h` or using `build_opt.h`