You probably will need to write your own code, since it will be specific to your setup. To help you get started, I suggest looking at the example sketches in our Arduino library for the Pololu QTR Reflectance Sensors to understand how the library works. You can find the library’s documentation linked on the GitHub page or here. Also, you might consider looking at the “Example Project #1: Line Following” section in our 3pi Robot User’s Guide, which explains how the line-following algorithm works, especially if this is your first time programming a line-following robot.