He thanks for the reactions. I've been looking at LED drivers, but have a hard time finding a good explanation as to how they work. And how i could control them, does any have a link with a good tutorial?
Just now i found the microdelay() function which compleetly removes the flickering of the leds but ofcourse doesn't increase brightness. Turn side on this is that i just increased the amount of leds from 12 to 20 (5 pins) without a great loss in brightness, if i can increase this to 56 (8 pins) without any big loss in brightness i could solve it with just putting brighter leds in it (now im just using basic red leds).