Add documentation for firmware changes

Firmware/README.md

@@ -0,0 +1,34 @@
+## Firmware
+
+The firmware used for driving the RepRap board is [Marlin](http://marlinfw.org/).
+
+### Marlin 1.1.1
+
+#### changes
+
+|file             |original value                                              |value|
+|-----------------|------------------------------------------------------------|-----------------------------------|
+|Configuration.h  |//#define ENDSTOPPULLUP_XMAX                                |#define ENDSTOPPULLUP_XMAX         |
+|                 |//#define ENDSTOPPULLUP_YMAX                                |#define ENDSTOPPULLUP_YMAX         |
+|                 |//#define ENDSTOPPULLUP_ZMAX                                |#define ENDSTOPPULLUP_ZMAX         |
+|                 |//#define ENDSTOPPULLUP_XMIN                                |#define ENDSTOPPULLUP_XMIN         | 
+|                 |//#define ENDSTOPPULLUP_YMIN                                |#define ENDSTOPPULLUP_YMIN         |
+|                 |//#define ENDSTOPPULLUP_ZMIN                                |#define ENDSTOPPULLUP_ZMIN         |
+|                 |//#define ENDSTOPPULLUP_ZMIN_PROBE                          |#define ENDSTOPPULLUP_ZMIN_PROBE   |
+|                 |#define Y_MIN_ENDSTOP_INVERTING false                       |#define Y_MIN_ENDSTOP_INVERTING true|
+|                 |#define X_MAX_ENDSTOP_INVERTING false                       |#define X_MAX_ENDSTOP_INVERTING true|
+|                 |#define Y_MAX_ENDSTOP_INVERTING false                       |#define Y_MAX_ENDSTOP_INVERTING true|
+|                 |#define Z_MIN_PROBE_ENDSTOP_INVERTING false                 |#define Z_MIN_PROBE_ENDSTOP_INVERTING true|
+|                 |#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80, 80, 4000, 500 } |#define DEFAULT_AXIS_STEPS_PER_UNIT  { 3.3333, 13.9, 8, 500 }|
+|                 |#define DEFAULT_MAX_FEEDRATE          { 300, 300, 5, 25 }   |#define DEFAULT_MAX_FEEDRATE          { 300, 300, 300, 25 }|
+|                 |#define INVERT_Z_DIR false                                  |#define INVERT_Z_DIR true|
+|                 |#define X_MAX_POS 1400                                      |#define X_MAX_POS 1280|
+|                 |#define Y_MAX_POS 2000                                      |#define Y_MAX_POS 3000|
+|                 |#define Z_MAX_POS 200                                       |#define Z_MAX_POS 4|
+|                 |#define HOMING_FEEDRATE_XY (50*60)                          |#define HOMING_FEEDRATE_XY (100*60)|
+
+### how to install 
+
+- download the firmware 1.1.1 on the marlin github repository [firmware](https://github.com/MarlinFirmware/Marlin/releases)
+- copy over the modified Configuration.h and Configuration_avd.h files
+- flash the firmware using the Arduino IDE