Created Standalone mode (markdown)

Standalone-mode.md

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+The most curious concept of Proxmark3 is the standalone mode functionalities.
+
+With a battery power option, your device can enter custom standalone function.  This means no need for the full Proxmark3 client.  The standalone mode is usually limited to a certain function, like the developer wanted it. 
+This also means the user interaction with the device is limited to 4 leds (A,B,C,D) and button presses. 
+Usually the button press is short,  long or multiple (twice).   All standalone modes uses this differently and is hard to find out what is what.
+Some community efforts has been done to document these.
+
+Hacker warehouse did a nice video
+[hacker warehouse video on youtube](https://www.youtube.com/watch?v=W22juSqhJSA)
+
+Troy also has a nice image of the leds,
+[led image for LF SAMMY_RUN](https://twitter.com/waveguyd/status/1051546698500067328)
+
+A forum user.
+[](http://www.proxmark.org/forum/viewtopic.php?pid=9438#p9438)
+
+The user Tinker
+[blogpost about badge cloning by Tinker](https://www.tinker.sh/badge-cloning-clone-hid-prox-with-proxmark3-rvd4/)
+
+
+
+You can implement your own mode or you can use others already implemented modes.
+
+For any iceman based repo the current most popular public standalone modes is quite easy to compile and install.
+In this repo its even easier than before.  The default standalone mode is LF_SAMMYRUN,  which gives READ/SIM of LF HID26 tags.
+
+
+If you want to write and implement your own standalone mode,  the best starting point is to read and understand the readme document found here.
+Ref: [Standalone mode - readme](https://github.com/RfidResearchGroup/proxmark3/tree/master/armsrc/Standalone/readme.md)