Update README.md

README.md

@@ -1,6 +1,12 @@
 # Ev3 print3rbot
-Python code for the EV3-Print3rbot, based on ev3dev project.
-It is using the [Python API](https://github.com/ddemidov/ev3dev-lang-python) from @ddemidov. To install it:
+
+Python code for the EV3-Print3rbot, based on the [ev3dev project](http://ev3dev.org).
+
+## Dependencies
+
+The ev3dev version must be at least [ev3dev-jessie-2015-05-01](https://github.com/ev3dev/ev3dev/releases/tag/ev3dev-jessie-2015-05-01).
+
+The code uses the [ev3dev Python API](https://github.com/ddemidov/ev3dev-lang-python) from @ddemidov. To install it:
 
 * Prerequisites:
 ```
@@ -12,4 +18,31 @@ apt-get install libboost-python-dev python-setuptools python-pil
 easy_install http://ddemidov.github.io/ev3dev-lang-python/python_ev3dev-latest.egg
 ```
 
+## Usage
+
+### Drawing an SVG image
+
+The EV3 Print3rbot can draw directly from SVG images. The images must contain only paths without transformations. To convert any SVG image, you can use inkscape in command line:
+```
+inkscape --verb=EditSelectAll --verb=ObjectToPath --verb=SelectionUnGroup --verb=FileSave --verb=FileClose --verb=FileQuit myfile.svg
+```
+Make sure that Inkscape is configured with "Transforms -> Store transformation" set to "Optimized" to remove all transformations in the process.
+
+The image will be automatically resized to fit in the robot drawing area. To draw an image, use the code:
+```
+wri = Writer(calibrate = True)
+wri.draw_image(image_file = 'images/test.svg')
+```
+
+### Using mouse as input
+
+The robot can use mouse as input. The code is based on the [evdev package](https://pypi.python.org/pypi/evdev) (included in the source). To use mouse as input, use the code:
+
+```
+wri = Writer(calibrate = True)
+wri.follow_mouse()
+```
+
+## Building instructions
+
 See [the project page](http://www.ev3dev.org/projects/2015/05/06/EV3-Print3rbot/) for building instructions.