VRV system control from KNX bus with CoolMaster

if not cm then
  require('serial')
  require('genohm-scada.eibdgm')
 
  -- knx and coolmaster mapping
  knxtocm = {}
  cmtoknx = {}
 
  -- value mapping
  modetotext = { [0] = 'cool', [1] = 'dry', [2] = 'heat' }
  texttomode = { cool = 0, dry = 1, heat = 2 }
  speedtotext = { [0] = 'l', [1] = 'm', [2] = 'h', [3] = 'a' }
  texttospeed = { low = 0, med = 1, high = 2, auto = 3 }
 
  -- get all tagged objects and set mapping
  for _, object in ipairs(grp.tag('VRV')) do
    local address, fn, stat = unpack(object.name:split(' '))
 
    if address ~= 'all' then
      address = tonumber(address)
    end
 
    -- status object
    if stat then
      if not cmtoknx[ address ] then
        cmtoknx[ address ] = {}
      end
 
      cmtoknx[ address ][ fn ] = {
        id = object.id,
        value = grp.getvalue(object.id),
      }
    -- control object
    else
      knxtocm[ object.id ] = {
        address = address,
        fn = fn,
      }
    end
  end
 
  function updateknx(address, fn, value, datatype)
    local object = cmtoknx[ address ] and cmtoknx[ address ][ fn ] or nil
 
    -- object not found
    if not object then
      return
    end
 
    -- no value or same value, no update required
    if value == nil or object.value == value then
      return
    end
 
    -- save new value and write to knx
    object.value = value
    grp.write(object.id, value, datatype)
  end
 
  function parseline(line)
    local address, status, setpoint, temp, speed, mode
 
    address = line:sub(1, 3)
    address = tonumber(address)
 
    -- address is not a number, cannot parse line
    if not address then
      return
    end
 
    -- on/off status
    status = line:sub(5, 6):lower() == 'on'
    updateknx(address, 'on/off', status, dt.bool)
 
    -- setpoint is integer
    setpoint = line:sub(9, 10)
    setpoint = tonumber(setpoint)
    updateknx(address, 'temp', setpoint, dt.float16)
 
    -- room temp is float, separated by comma
    temp = line:sub(13, 17):gsub(',', '.')
    temp = tonumber(temp)
    updateknx(address, 'temp_room', temp, dt.float16)
 
    -- speed: low, med, high, auto
    speed = line:sub(20, 23):lower():trim()
    updateknx(address, 'fspeed', texttospeed[ speed ], dt.uint8)
 
    -- mode: cool, heat, fan, dry, auto
    mode = line:sub(25, 28):lower():trim()
    updateknx(address, 'mode', texttomode[ mode ], dt.uint8)
  end
 
  -- read single line from serial
  function readline()
    local line, timeout, char, err
 
    line = {}
    timeout = 10
 
    -- read until timeout or full line
    while timeout > 0 do
      -- get single char from serial
      char, err = cm:read(1, 0.1)
 
      -- read timeout
      if not char then
        timeout = timeout - 1
      -- end-of-line
      elseif char == '\n' then
        break
      -- ignore carriage return
      elseif char ~= '\r' then
        table.insert(line, char)
      end
    end
 
    -- read ok
    if timeout > 0 then
      return table.concat(line)
    end
  end
 
  -- read current status
  function readstat()
    local line
    cm:flush()
    cm:write('stat\r\n')
 
    -- read until error or end of stat
    while true do
      line = readline()
 
      -- timeout or end occured
      if not line or line == 'OK' then
        break
      end
 
      parseline(line)
    end
  end
 
  -- send single cmd to coolmaster
  function writecmd(cmd)
    local result
 
    cm:flush()
    cm:write(cmd .. '\r\n')
 
    readline() -- command echo
    result = readline() -- command result
    readline() -- new line prompt
 
    return result
  end
 
  -- handle group writes
  function eventhandler(event)
    local object, cmd, value, param
 
    object = knxtocm[ event.dstraw ]
    -- knx object not mapped, ignore
    if not object then
      return
    end
 
    -- on/off - boolean
    if object.fn == 'on/off' then
      value = knxdatatype.decode(event.datahex, dt.bool)
      cmd = value and 'on' or 'off'
    -- setpoint - floating point
    elseif object.fn == 'temp' then
      value = knxdatatype.decode(event.datahex, dt.float16)
      param = string.format('%.2f', value)
      cmd = 'temp'
    -- mode (fan, dry, auto)
    elseif object.fn == 'mode' then
      value = knxdatatype.decode(event.datahex, dt.uint8)
      cmd = modetotext[ value ]
    -- speed (low, medium, high, auto)
    elseif object.fn == 'fspeed' then
      value = knxdatatype.decode(event.datahex, dt.uint8)
      param = speedtotext[ value ]
 
      if param then
        cmd = 'fspeed'
      end
    end
 
    -- got valid command
    if cmd then
      -- all allows only on/off
      if object.address == 'all' then
        cmd = 'all' .. cmd
      -- append address to command
      else
        cmd = cmd .. ' ' .. object.address
      end
 
      -- append additional parameter if set
      if param then
        cmd = cmd .. ' ' .. param
      end
 
      writecmd(cmd, true)
    end
  end
 
  -- coolmaster serial connection
  cm = serial.open('/dev/RS232', { baudrate = 9600 })
 
  -- knx connection
  client = eibdgm:new()
  client:sethandler('groupwrite', eventhandler)
 
  -- start-up time
  sec, usec = os.microtime()
end
 
-- handle knx
client:step()
 
-- read stats every 3 seconds
diff = os.udifftime(sec, usec)
if diff < 0 or diff >= 3 then
  readstat()
  sec, usec = os.microtime()
end