fadein-fadeout effect on nodeMCU using WS2812 LED

nodemcu-ws2812-fader.lua

-- nodeMCU specific
ws2812.init()
-- 4 LEDS, 3 bytes per LED
buffer = ws2812.newBuffer(4, 3)
green,red,blue = 255,64,192
buffer:fill(green,red,blue)

function brightness (x, max)
  return math.floor((math.floor((x * max) / 100)*2) + 1)/2
end

step = 3
dir = 1
cntr = 0

r = red
g = green
b = blue

function fader()

    if cntr > 100 then
        dir = -1
        cntr = 100
    elseif cntr < 0 then
        dir = 1
        cntr = 0
    end

    r = brightness(cntr, red)
    g = brightness(cntr, green)
    b = brightness(cntr, blue)

    cntr = cntr + (step*dir)

    buffer:fill(g,r,b)
    ws2812.write(buffer)
end

tmr.alarm(0,25,1,fader)