HDL Buspro gateway integration with LM5

Code:
local socket = require('socket')

local crc16 = require('encdec').crc16

local ifinfo = require('ifinfo')



HDL = {

  -- destination ip

  dstip = '192.168.0.2',

  -- packet constant data

  magic = 'HDLMIRACLE',

  lcode = string.char(0xAA, 0xAA),

  -- source device settings

  srcsubnet = 1,

  srcdevice = 254,

  devicetype = 0xFFFE,

  -- command types

  cmd = {

    chanreg = 0x0031, -- single channel regulate

    chanregreply = 0x0032, -- single channel regulate answerback

    chanstat = 0x0033, -- read status of single channel targets

    chanstatreply = 0x0034, -- single channel targets status answerback

  }

}



HDL.init = function()

  local info, chunk, chunks



  info = ifinfo()



  if not info or not info.eth0 then

    error('cannot get interface info')

  end



  -- ip header

  HDL.iphdr = ''

  -- broadcast address

  HDL.bcast = info.eth0.bcast



  -- split ip address into chunks

  chunks = info.eth0.inetaddr:split('.')



  -- add ip address chunks

  for i = 1, 4 do

    chunk = tonumber(chunks[ i ])

    HDL.iphdr = HDL.iphdr .. string.char(chunk)

  end

end



HDL.decode = function(packet)

  local len, data, src, crc



  -- primary header

  if packet:sub(5, 14) ~= HDL.magic then

    return nil, 'magic'

  end



  -- leading code

  if packet:sub(15, 16) ~= HDL.lcode then

    return nil, 'lcode'

  end



  -- get data length and check against

  len = packet:byte(17)

  if len and len + 16 ~= packet:len() then

    return nil, 'len'

  end



  -- get packet data and check crc

  data = packet:sub(17, len + 14)

  crc = packet:byte(len + 15) * 0x100 + packet:byte(len + 16)

  if crc16(data) ~= crc then

    return nil, 'crc'

  end



  -- return parsed packet

  return {

    srcip = string.format('%d.%d.%d.%d', packet:byte(1, 4)),

    srcsubnet = packet:byte(18),

    srcdevice = packet:byte(19),

    devicetype = (packet:byte(20) * 0x100 + packet:byte(21)),

    opcode = (packet:byte(22) * 0x100 + packet:byte(23)),

    dstsubnet = packet:byte(24),

    dstdevice = packet:byte(25),

    additional = packet:sub(26, len + 14)

  }

end



HDL.word = function(v)

  return string.char(bit.band(bit.rshift(v, 8), 0xFF), bit.band(v, 0xFF))

end



HDL.encode = function(cmd, dstsubnet, dstdevice, extra)

  local packet, len, crc, data



  -- perform init if required

  if not HDL.iphdr then

    HDL.init()

  end



  -- start packet: ip, magic and leading code

  packet = { HDL.iphdr, HDL.magic, HDL.lcode }

  -- base data

  data = string.char(HDL.srcsubnet, HDL.srcdevice) ..

    HDL.word(HDL.devicetype) ..

    HDL.word(cmd) ..

    string.char(dstsubnet, dstdevice)



  -- add extra data parameters

  if type(extra) == 'string' then

    data = data .. extra

  end



  -- calculate length and crc

  len = string.char(data:len() + 3)

  crc = crc16(len .. data)



  table.insert(packet, len)

  table.insert(packet, data)

  table.insert(packet, HDL.word(crc))



  return table.concat(packet)

end



HDL.send = function(packet)

  local client = socket.udp()

  client:sendto(packet, HDL.dstip, 6000)

end



HDL.chanreg = function(dstsubnet, dstdevice, chan, value, delay)

  local extra, packet

  delay = delay or 0



  if type(value) == 'boolean' then

    value = value and 100 or 0

  end



  extra = string.char(chan, value) .. HDL.word(delay)

  packet = HDL.encode(HDL.cmd.chanreg, dstsubnet, dstdevice, extra)



  HDL.send(packet)

end