rubberTurtleFarm 1.4.0

local t = turtle

local function forward(x)
    for i = 1, x do
        t.forward()
    end
end

local function rTurn(x)
    for i = 1, x do
        t.turnRight()
    end
end

local function lTurn(x)
    for i = 1, x do
        t.turnLeft()
    end
end

local function up(x)
    for i = 1, x do
        t.up()
    end
end

local function down(x)
    for i = 1, x do
        t.down()
    end
end

local function back(x)
    for i = 1, x do
        t.back()
    end
end

local function gotoStart()
    rs.setAnalogOutput("left", 0)
    os.sleep(1)
    up(2)
    back(1)
    lTurn(1)
    forward(1)
end

local function rowUp()
    for i = 1, 4, 1 do
        t.dig()
        up(1)
    end
end

local function rowDown()
    for i = 1, 4, 1 do
        t.dig()
        down(1)
    end
end

local facing = t.detect()

local height = t.detect(down)

local function upDown()
    if height == true then
        rowUp()
    else
        rowDown()

local function harvest(x)
    for i = 1, x do
        rTurn(1)
        if facing == true then
            upDown()
        else
            forward(1)
            lTurn(1)
            upDown()
        end
    end
end

local function gotoHome()
    back(2)
    lTurn(1)
    forward(1)
    down(5)
    os.sleep(1)
    rs.setAnalogOutput("left", 15)
    os.sleep(3600)
end

while true do
    gotoStart()
    rowUp()
    harvest(6)
    gotoHome()
end