Modbus, reading registers with strings

[admin]

More universal solution:

Code:

require('luamodbus')
mb = luamodbus.tcp()

mb:open('192.168.2.1', 502)
mb:connect()

function readstring(mb, address, length)
  local data = { mb:readregisters(address, length) }
  local bytes = {}

  for _, reg in ipairs(data) do
    if type(reg) == 'number' then
      -- high 8 bits
      local b1 = bit.band(bit.rshift(reg, 8), 0xFF)
      if b1 > 0 then
        bytes[ #bytes + 1 ] = b1
      end

      -- low 8 bits
      local b2 = bit.band(reg, 0xFF)
      if b2 > 0 then
        bytes[ #bytes + 1 ] = b2
      end
    end
  end

  -- convert table of byte values to string
  return string.char(unpack(bytes))
end

result = readstring(mb, 71, 16)
log(result)

mb:close()