NodeMCU HD44780

hd44780.lua

local bor, band, bnot = bit.bor, bit.band, bit.bnot

local function write4bits(self, bits, char_mode)
  tmr.delay(1000)
  gpio.write(self.pin_rs, char_mode and gpio.HIGH or gpio.LOW)

  for n = 1, 2 do
    for i, pin in ipairs(self.pin_db) do
      local j = (2-n)*4 + (i-1)
      local val = (bit.isset(bits, j))
      gpio.write(pin, val and gpio.HIGH or gpio.LOW)
    end
    gpio.write(self.pin_e, gpio.LOW)
    tmr.delay(1000)
    gpio.write(self.pin_e, gpio.HIGH)
    tmr.delay(1000)
    gpio.write(self.pin_e, gpio.LOW)
    tmr.delay(37000)
  end
end

local function home(self)
  write4bits(self, 0x02)
  tmr.delay(3000000)
end    

local function clear(self)
  write4bits(self, 0x01)
  tmr.delay(3000000)
end

local function message(self, text)
  tmptext = text:gsub("\n", string.char(0xC0))
  for i = 1, #tmptext do
    local c = tmptext:byte(i)
    write4bits(self, c, (c ~= 0xC0))
  end
end

function init(pin_rs, pin_e, pin_db)
  local self = {
    pin_rs = pin_rs,
    pin_e = pin_e,
    pin_db = pin_db
  }
  
  gpio.mode(self.pin_rs, gpio.OUTPUT)
  gpio.mode(self.pin_e, gpio.OUTPUT)
  for _, pin in ipairs(self.pin_db) do
    gpio.mode(pin, gpio.OUTPUT)
  end

  self.begin = begin
  self.home = home
  self.clear = clear
  self.message = message
  self.write4bits = write4bits

  self:write4bits(0x33) -- initialization
  write4bits(self, 0x32) -- initialization
  write4bits(self, 0x28) -- 2 line 5x7 matrix
  write4bits(self, 0x0C) -- turn cursor off 0x0E to enable cursor
  write4bits(self, 0x06) -- shift cursor right

  self:clear()
  return self
end

m = init(1, 2, {3, 4, 5, 6})
m:message("Hello World\nFrom ESP8266")

Translated https://github.com/Tieske/rpi-gpio/blob/master/lua/module/lcd-hd44780.lua from the Raspberry Pi to ESP8266 NodeMCU. Left most of the functions out because they do not fit into memory...

Why so mutch delay? Example Clear and Home needs only 1.52ms not 3s!

Nice work! But could you explain line 36 a bit? Would'nt write4bits(self, c, 1) suffice?

EDIT: Ahh got it. Forces the line break if neccessary.