Modbus TCP Polling Delay

[admin]

If you want quick polling you need to use one resident script per each connection because Modbus mapper can only poll one TCP device at a time.
Use this example as a starting point. The connection is kept open between requests. Multiple registers are read at once to speed things up.

Code:

if not mb then
  require('luamodbus')
  mb = luamodbus.tcp()
  mb:open('192.168.0.9')
  
  res, err = mb:connect()
  if not res then
    mb:close()
    mb = nil
    log('connect failed', err)
  end
end

if mb then
  v1, v2, v3 = mb:readregisters(10, 3)

  if v1 ~= nil then
    grp.checkupdate('1/1/1', v1)
    grp.checkupdate('1/1/2', v2)
    grp.checkupdate('1/1/3', v3)
  else
    mb:close()
    mb = nil
    log('read failed', v2)
  end
end