I have some resources to get you going.
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I wrote a long article covering pretty much all aspects of the line tracker: https://renegaderobotics.org/vex-sensors-line-tracker/
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@tabor473 was kind enough to share his on-field calibration code for my blog, which you can find here: https://renegaderobotics.org/line-tracker-field-calibration-code/
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The article in #1 above has a link to it, but here it is again – Free Range Robotics line tracker PID guide (it’s excellent): http://robotics.org.nz/tips-and-tricks/programming-guides/62-line-following-with-robotc
FYI - the “RobotC” channel on the Forum can only be answered by RobotC staff.