nodemcu-firmware/lua_modules/bh1750/bh1750.lua

-- ***************************************************************************
-- BH1750 module for ESP8266 with nodeMCU
-- BH1750 compatible tested 2015-1-22
--
-- Written by xiaohu
--
-- MIT license, http://opensource.org/licenses/MIT
-- ***************************************************************************
local moduleName = ...
local M = {}
_G[moduleName] = M
    --I2C slave address of GY-30
    local GY_30_address = 0x23
    -- i2c interface ID
    local id = 0
    --LUX
    local l
    --CMD
    local CMD = 0x10
    local init = false
    --Make it more faster
    local i2c = i2c
    function M.init(sda, scl)
        i2c.setup(id, sda, scl, i2c.SLOW)
    --print("i2c ok..")
    init = true
end
local function read_data(ADDR, commands, length)
    i2c.start(id)
    i2c.address(id, ADDR, i2c.TRANSMITTER)
    i2c.write(id, commands)
    i2c.stop(id)
    i2c.start(id)
    i2c.address(id, ADDR,i2c.RECEIVER)
    tmr.delay(200000)
    local c = i2c.read(id, length)
    i2c.stop(id)
    return c
end
local function read_lux()
    local dataT = read_data(GY_30_address, CMD, 2)
    --Make it more faster
    local UT = dataT:byte(1) * 256 + dataT:byte(2)
    l = (UT*1000/12)
    return(l)
end
function M.read()
    if (not init) then
        print("init() must be called before read.")
    else
        read_lux()
    end
end
function M.getlux()
    return l
end
return M