Update README.md

README.md

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 # k380-fn-lock-for-windows
  Lock Fn keys on K380 (for windows)
+
+## Goal
+This program locks the fn key for the Logitech K380 bluetooth keyboard on Windows. 
+Having the F1-F12 without pressing the Fn key is nice for developers.
+
+I wanted a simple way to do the same as the Logitech Options/Options+ softwares WITHOUT their continuously running processes.
+
+## How to use
+Running `setFnKeys.exe` will lock Fn key till next reboot.  
+Revert with `setMediaKeys.exe` to unlock and restore media keys.
+
+## How to build
+- prerequisite : install mingw
+- build setFnKeys.exe with :   
+    `gcc main.c -o dist/setFnKeys.exe -I hidapi/include -L hidapi/x86 -lhidapi`
+- build setMediaKeys.exe with :   
+    `gcc main.c -D setMediaKeys -o dist/setMediaKeys.exe -I hidapi/include -L hidapi/x86 -lhidapi`
+
+# Inspiration
+code from : https://github.com/keighrim/k810fn/blob/master/win/k810fn/k810fnCLI.cpp   
+values from : https://github.com/jergusg/k380-function-keys-conf/blob/master/k380_conf.c