Modbus Connector

Raphaela Brückl

Modbus is an open communication protocol that is widely used in industrial automation due to its ease of implementation, reliability and robustness. It allows the transmission of data between different devices via Ethernet connections and serial interfaces such as RS-232 or RS-485. Typically, information such as measured values, states and control commands are transmitted via Modbus in order to monitor and control processes.

Supported function codes

Modbus defines a variety of function codes that allow different types of data transfers between server and client. The Autonoma Modbus Connector supports the most commonly used function codes:

  • Read Coils (0x01)
  • Read Discrete Inputs (0x02)
  • Read Holding Registers (0x03)
  • Read Input Registers (0x04)

With the function codes 0x01 and 0x02 typically status information and binary input or output signals can be read. The function codes 0x03 and 0x04 are typically used to read measured values or other data provided by the Modbus device.

Modbus Configuration

Example Siemens Smartmeter

An example of a Modbus device that can be easily integrated into the Autonoma Cloud using our Modbus Connector is the PAC2200 Smartmeter from Siemens. This device can be used to measure currents, voltages and frequency, among other things. With the Autonoma Modbus Connector, you can easily read out these values, store them in the cloud and display them. The configuration of the individual measured values can be done as usual in the DCP in the guided menu.

Easy handling of special cases

Although the Modbus protocol provides a template for device manufacturers on how to make their data available, actual implementations often differ in practice. For example, it may happen that status values are not to be queried with function code 0x01 or 0x02, but with function code 0x03. This subsequently leads to the individual bit having to be masked out manually afterwards. In order to eliminate the associated effort for your customers, our connector also offers the possibility to directly read out individual bits with the function codes 0x03 and 0x04. In addition to bit, all other common data types such as: Byte, Integer, Float and Strings are supported. To ensure maximum compatibility the correct byte and word order can always be set for relevant data types.

Support of Modbus TCP & Modbus RTU

Another highlight of the Autonoma Modbus Connector is that both devices connected via Ethernet (Modbus TCP) and devices connected serially (Modbus RTU) can be integrated. By supporting both technologies we can guarantee maximum flexibility.

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