modbus

Modbus Input Plugin

The Modbus plugin collects Discrete Inputs, Coils, Input Registers and Holding Registers via Modbus TCP or Modbus RTU/ASCII.

Configuration

[[inputs.modbus]]
  ## Connection Configuration
  ##
  ## The plugin supports connections to PLCs via MODBUS/TCP or
  ## via serial line communication in binary (RTU) or readable (ASCII) encoding
  ##
  ## Device name
  name = "Device"

  ## Slave ID - addresses a MODBUS device on the bus
  ## Range: 0 - 255 [0 = broadcast; 248 - 255 = reserved]
  slave_id = 1

  ## Timeout for each request
  timeout = "1s"

  ## Maximum number of retries and the time to wait between retries
  ## when a slave-device is busy.
  # busy_retries = 0
  # busy_retries_wait = "100ms"

  # TCP - connect via Modbus/TCP
  controller = "tcp://localhost:502"

  ## Serial (RS485; RS232)
  # controller = "file:///dev/ttyUSB0"
  # baud_rate = 9600
  # data_bits = 8
  # parity = "N"
  # stop_bits = 1
  # transmission_mode = "RTU"


  ## Measurements
  ##

  ## Digital Variables, Discrete Inputs and Coils
  ## measurement - the (optional) measurement name, defaults to "modbus"
  ## name        - the variable name
  ## address     - variable address

  discrete_inputs = [
    { name = "start",          address = [0]},
    { name = "stop",           address = [1]},
    { name = "reset",          address = [2]},
    { name = "emergency_stop", address = [3]},
  ]
  coils = [
    { name = "motor1_run",     address = [0]},
    { name = "motor1_jog",     address = [1]},
    { name = "motor1_stop",    address = [2]},
  ]

  ## Analog Variables, Input Registers and Holding Registers
  ## measurement - the (optional) measurement name, defaults to "modbus"
  ## name        - the variable name
  ## byte_order  - the ordering of bytes
  ##  |---AB, ABCD   - Big Endian
  ##  |---BA, DCBA   - Little Endian
  ##  |---BADC       - Mid-Big Endian
  ##  |---CDAB       - Mid-Little Endian
  ## data_type  - INT16, UINT16, INT32, UINT32, INT64, UINT64, FLOAT32-IEEE (the IEEE 754 binary representation)
  ##              FLOAT32 (deprecated), FIXED, UFIXED (fixed-point representation on input)
  ## scale      - the final numeric variable representation
  ## address    - variable address

  holding_registers = [
    { name = "power_factor", byte_order = "AB",   data_type = "FIXED", scale=0.01,  address = [8]},
    { name = "voltage",      byte_order = "AB",   data_type = "FIXED", scale=0.1,   address = [0]},
    { name = "energy",       byte_order = "ABCD", data_type = "FIXED", scale=0.001, address = [5,6]},
    { name = "current",      byte_order = "ABCD", data_type = "FIXED", scale=0.001, address = [1,2]},
    { name = "frequency",    byte_order = "AB",   data_type = "UFIXED", scale=0.1,  address = [7]},
    { name = "power",        byte_order = "ABCD", data_type = "UFIXED", scale=0.1,  address = [3,4]},
  ]
  input_registers = [
    { name = "tank_level",   byte_order = "AB",   data_type = "INT16",   scale=1.0,     address = [0]},
    { name = "tank_ph",      byte_order = "AB",   data_type = "INT16",   scale=1.0,     address = [1]},
    { name = "pump1_speed",  byte_order = "ABCD", data_type = "INT32",   scale=1.0,     address = [3,4]},
  ]

Metrics

Metric are custom and configured using the discrete_inputs, coils, holding_register and input_registers options.

Usage of data_type

The field data_type defines the representation of the data value on input from the modbus registers. The input values are then converted from the given data_type to a type that is apropriate when sending the value to the output plugin. These output types are usually one of string, integer or floating-point-number. The size of the output type is assumed to be large enough for all supported input types. The mapping from the input type to the output type is fixed and cannot be configured.

Integers: INT16, UINT16, INT32, UINT32, INT64, UINT64

These types are used for integer input values. Select the one that matches your modbus data source.

Floating Point: FLOAT32-IEEE

Use this type if your modbus registers contain a value that is encoded in this format. This type always includes the sign and therefore there exists no variant.

Fixed Point: FIXED, UFIXED (FLOAT32)

These types are handled as an integer type on input, but are converted to floating point representation for further processing (e.g. scaling). Use one of these types when the input value is a decimal fixed point representation of a non-integer value.

Select the type UFIXED when the input type is declared to hold unsigned integer values, which cannot be negative. The documentation of your modbus device should indicate this by a term like 'uint16 containing fixed-point representation with N decimal places'.

Select the type FIXED when the input type is declared to hold signed integer values. Your documentation of the modbus device should indicate this with a term like 'int32 containing fixed-point representation with N decimal places'.

(FLOAT32 is deprecated and should not be used any more. UFIXED provides the same conversion from unsigned values).

Example Output

$ ./telegraf -config telegraf.conf -input-filter modbus -test
modbus.InputRegisters,host=orangepizero Current=0,Energy=0,Frecuency=60,Power=0,PowerFactor=0,Voltage=123.9000015258789 1554079521000000000