Gettingstarted OLED display U8GLib Lua

--Connecting 128x64 OLED disp to ESP8266-12E nodemcu DevKit from banggood
-- modified by electromania 
-- original code from 
--https://github.com/nodemcu/nodemcu-firmware/tree/master/lua_examples/u8glib 
-- setup SPI and connect display

     -- D3 of ESP to RES of Display
     -- D4 of ESP to DC of Display
     -- D5 of ESP to SCL of Display  Hardware SPI CLK  = GPIO14 
     -- D7 of ESP to SDA of Display  Hardware SPI MOSI = GPIO13
     -- Hardware SPI MISO = GPIO12 (not used)

     -- CS, D/C, and RES can be assigned freely to available GPIOs

     function init_spi_display()

     local cs  = 8 -- GPIO15, pull-down 10k to GND     worked even without 10k pulldown resistor
     local dc  = 4 -- GPIO2        -- D4-DC
     local res = 3 -- GPIO16       -- D3-RES

     spi.setup(1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, spi.DATABITS_8, 0)
     disp = u8g.ssd1306_128x64_spi(cs, dc, res)
end


-- graphic test components
function prepare()
     --disp:setFont(u8g.font_6x10)
     disp:setFont(u8g.font_chikita)
     disp:setFontRefHeightExtendedText()
     disp:setDefaultForegroundColor()
     disp:setFontPosTop()
end


function extra_page(a)
     disp:setFont(u8g.font_chikita)
     disp:setScale2x2()
     disp:drawStr(5, 12+a, "Electromania")
     disp:undoScale()
end


-- the draw() routine
function draw(draw_state)
     prepare()
     extra_page(bit.band(draw_state, 1))
end

function graphics_test(delay)
     print("--- Starting Graphics Test ---")

     -- cycle through all components
     local draw_state
     for draw_state = 0, 150, 1 do   -- this was just to give a little vibrating animation effect 
          disp:firstPage()
          repeat
               draw(draw_state)
          until disp:nextPage() == false
    
          tmr.delay(delay)
          -- re-trigger Watchdog!
          tmr.wdclr()
     end

     print("--- Graphics Test done ---")
end

init_spi_display()
graphics_test(50000)