root/Lego/lua/follow_simple.lua

-- A simple line following program.
-- It works with the standard NXT bot.
-- Place the bot on the test pad, with the wheels
-- on the start line facing forward.
-- Then start the program.

-- author: Jan-Klaas Kollhof
-- last changed by: $LastChangedBy$
-- last changed date: $Date$
-- revision: $Revision$

LightThreshold=500
Fast=75
Slow=20



function follow_simple()

    nxt.InputSetType(3, 1)
    nxt.InputSetDir(3, 1, 1)
    nxt.InputSetState(3, 1, 0)

    -- no speed regulation, this seems important
    -- for some reason
    nxt.OutputSetRegulation(2, 0, 1 )
    nxt.OutputSetRegulation(3, 0, 1 )

    
    -- lets turn 90 deg left

    -- now follow the line
    nxt.OutputSetSpeed(2, 32, Fast)
    nxt.OutputSetSpeed(3, 32, Fast)

    repeat
        if(nxt.InputGetStatus( 3 ) > LightThreshold) then
            nxt.OutputSetSpeed(2, 32, Slow)
        else
            nxt.OutputSetSpeed(2, 32, Fast)
        end

    until(nxt.ButtonRead() == 8)

    nxt.OutputSetSpeed(2, 0, 0)
    nxt.OutputSetSpeed(3, 0, 0)

end

follow_simple()