Requesting data from Aranet PRO Modbus TCP/IP server

Important notes for the client side:

Parameter	Value
Register size	16 bits
Unit ID (slave ID)	1 (not changeable)
Supported functions	Read discrete inputs (code: 2), read input registers (code: 4)
Supported data types	Discrete inputs, input registers (any address in the supported range of 0—65535)
Endianness	Big-endian with high word first (high byte first or high word first for 2 registers/32-bit values)

Used Modbus TCP exceptions

• Unsupported function requested → ILLEGAL_FUNCTION.
• Unavailable registry address requested → ILLEGAL_DATA_ADDRESS. This exception is also sent if a particular address is colliding with any other registry address.
• Uninitialized registry address requested → ILLEGAL_DATA_VALUE. The address exists, but valid data of measurement has not been assigned yet.

Custom address-to-measurements mapping: Input registers

Below is an example of an uploaded custom address-to-measurements mapping configuration JSON file used for input registers (example with three 2×16-bit wide registries):

{ 
  "inputRegisters": {
    "1056849": {
      "battCharge": { // Registry address: 30044
        "dataType": "int32",
        "multiplier": 100,
        "offset": 4
      },
      "offset": 40,
      "rssi": { // Registry address: 30046
        "dataType": "int32",
        "multiplier": 1,
        "offset": 6
      },
      "time": { // Registry address: 30048
        "dataType": "uint32",
        "multiplier": 1,
        "offset": 8
      }
    },
    "offset": 30000
  }
}

Representation in a Modbus client application is shown in Fig. 3.

Figure 3: Modbus client application view with an example configuration

Custom address-to-measurements mapping: Discrete inputs

Example of uploaded custom mapping configuration for Discrete inputs:

"discreteInputs": {
  "4196581": {
    "offset": 20,
    "rssiAlarm": { // Registry address: 10020
      "dataType": "bit",
      "multiplier": 1,
      "offset": 1
    }
  },
  "6292285": {
    "offset": 20,
    "rssiAlarm": { // Registry address: 10021
      "dataType": "bit",
      "multiplier": 1,
      "offset": 0
    }
  },
  "offset": 10000
}

Figure 4: Modbus client application view with an example configuration