Universal Modbus TCP/RTU Slave

[admin]

Multiple resident scripts can't share the same RS-485 port. It should be enough just to block writing as needed.

Replace the whole handlers.writeregister function with this, modify writeallowed logic as needed.

Code:

local function writeallowed(slaveid)
  if slaveid == 1 then
    return grp.getvalue('1/1/1')
  elseif slaveid == 2 then
    return grp.getvalue('1/1/2')
  end
end

handlers.writeregister = function(slaveid, fncode, data)
  if #data ~= 4 then
    return
  end

  local addr = touint16(data, 1)
  local map = getmapping(slaveid, fncode)

  if not map or not map[ addr ] then
    return excodes.illegaldataaddress
  end

  local mapobj = map[ addr ]

  if mapobj.len ~= 1 then
    return excodes.illegaldataaddress
  end

  if writeallowed(slaveid) then
    writevalue(mapobj, data, 3)
  end

  return data
end

Replace the whole handlers.writeregisters function with this.

Code:

handlers.writeregisters = function(slaveid, fncode, data)
  if #data < 5 then
    return
  end

  local addr = touint16(data, 1)
  local count = touint16(data, 3)
  local bytes = touint8(data, 5)

  if #data ~= (bytes + 5) then
    return
  end

  if count == 0 or count > limits.writeregisters or bytes ~= count * 2 then
    return excodes.illegaldataaddress
  end

  local map = getmapping(slaveid, fncode)

  if not map then
    return excodes.illegaldataaddress
  end

  if writeallowed(slaveid) then
    for i = 0, (count - 1) do
      local mapobj = map[ addr + i ]

      if mapobj and not mapobj.readonly then
        local offset = 6 + i * 2
        writevalue(mapobj, data, offset)
      end
    end
  end

  return data:sub(1, 4)
end