The use of length in LightUpLeds() doesn't look like int to me anyway.
In general I want to specify the light on time by looping through the process again and again. This is not very precise anyway and depends on the number of rows having to light up. Any recommendations for improvements?
It's passed to the function. I think it's not copied. There is made use of a pointer, but I am not sure. Or what do you mean?
void lightUpLeds(int drawLeds[][height*width][2], int length)