Updated Add own functionality (markdown)

Add-own-functionality.md

@@ -43,7 +43,23 @@ void userLoop()
 
 ### Internal Segments API
 
-TBD
+You can use Segments from your code to set different parts of the strip to different colors or effects.   
+This can be very useful for highly customized installations, clocks, ...   
+
+To set a segment, use `strip.setSegment(id, start, stop);`, where _id_ is the segment ID, _start_ is the first LED of the segment and _stop_ is the LED after the last one in the segment.
+
+To edit the configuration of a segment, use:
+```cpp
+WS2812FX::Segment& seg = strip.getSegment(id);
+//set color (i=0 is primary, i=1 secondary i=2 tertiary)
+seg.colors[i] = ((myWhite << 24) | ((myRed&0xFF) << 16) | ((myGreen&0xFF) << 8) | ((myBlue&0xFF)));
+//set effect config
+seg.mode = myFxI;
+seg.speed = mySpeed;
+seg.intensity = myIntensity;
+seg.palette = myPaletteId;
+```
+Keep in mind that this will not cause interface updates as of 0.8.6. For that, you still need to use 'colorUpdated(1)'
 
 ### Create custom effects