require('serial')
  port = serial.open('/dev/RS485', { 
    baudrate = 9600,
    databits = 8,
    stopbits = 1,
    parity = 'none',
    duplex = 'half'
  })

log("Verbinding gemaakt")
     
function readdata(port) 
  local char, buf 

  buf = {} 

  while true do 
    char = port:read(1) 

    -- error (timeout) or newline, stop 
    if char == nil then 
      break 
    -- ignore cr char 
    elseif char ~= '\r' then
      table.insert(buf, char)
    end 
  end 

  return table.concat(buf) 
end 

data = readdata(port) 
log (data)

port:flush()