Simples Birch Farm

function refuel()
        if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < 1 then
                    repeat
                            turtle.select(1)
                            if turtle.getItemCount( turtle.getSelectedSlot() ) == 0 then
                                print("Out of fuel! Put fuel in first slot.")
                                print("Press any key to continue")
                                os.pullEvent("key")
                            else
                            end
                    until turtle.getItemCount( turtle.getSelectedSlot() ) > 0
                    print("refueling")
                    turtle.refuel()
        end
end

function sucker()
            c = 4
        for c = 4,1,-1 do
            turtle.suck()
            turtle.turnRight()
        end
end

a = 0

while true do
    local success, ifgravel = turtle.inspect()
    if ifgravel.name == "minecraft:log" then
            turtle.dig()
            turtle.digUp()
            turtle.up()
            a = a +1
            x=2
    else
        for b = a,1,-1 do
            turtle.down()
        end
        turtle.select(2)
        turtle.place()
        if x == 2 then
                turtle.turnRight()
                for T = 1,4,1 do
                        sucker()
                        turtle.forward()
                        sucker()
                        turtle.turnLeft()
                        turtle.forward()
                end
                turtle.turnLeft()
        end
        x = 1
        a = 0
        turtle.select(3)
        turtle.place()

        turtle.select(4)
        os.sleep(1)
    end
end