Modbus Protocol

Modicon (now Schneider Electric) developed the Modbus protocol in 1979 as a means for communicating with field devices over a single twisted pair wire. Since 2004, Modbus Organization is responsible for the development and update of the protocol. The open and royalty free serial communication protocol continues to be a popular communication standard to transfer discrete/analog I/O information between industrial devices.

Modbus devices operate in a master-slave (client-server) technique, where the master/client communicates with one or multiple slaves/servers. The master typically is a PLC, PC, DCS, or RTU, which initiates a request for data from a slave and only that particular slave/server responds to that query. The slave is any peripheral monitoring or measuring device (I/O transducer, sensors, valve, network drive or other devices).

Why Modbus Protocol stack is required for Industries?

One of the major advantages of the protocol is that it is open source. This can greatly reduce the need to buy unique chipsets or pay heavy royalty/licensing fees. Healthcare and home automation industries are also exploring the benefits offered by the Modbus protocol stack.

Benefits of Modbus protocol

The main reason Modbus is so successful is the fact that non-programmers can readily understand it. Even plant engineers who deal directly with meters, measuring devices, and other industrial assets could easily understand the concept of coils/registers and the simple commands to read and write them. Because of its universal nature, it has a number of benefits including the following:

• The open source nature of the protocol means that it is interoperable with a wide range of device types from any equipment vendor.
• Modbus specification is freely available for download and requires no subsequent licensing fees. The Modbus toolkit includes additional sample codes, diagnostics and implementation examples for Modbus Organization members. It is available for purchase by non-members.
• The simple messaging structure makes it easy to deploy compared to other protocol requiring a large learning curve.

Modbus protocol services provided by Utthunga

Before you decide on a Modbus solution, you need to consider various details like the devices that you are going to be monitoring and how they report back to you. Don’t worry about the intricacies of Modbus setup and use as our engineers can effectively put it all together for your real world needs. Considering both the hardware and software limitations and challenges, some of the Modbus protocol services that we offer are as mentioned below.

• Design and develop Modbus slave and master devices and applications on different embedded and PC based platforms
• Data modelling for the slaves
• Design and development of custom function codes
• Protocol stack porting and integration with the device application
• Capabilities and experience with all variants of Modbus (RTU, ASCII and TCP)
• Converting Modbus to/from other protocols
• Enabling OPC UA servers and other applications with Modbus data collection capabilities

Technical Specification of Modbus master and slave stacks:

1. Developed in ANSI C and .NET. The ANSI C version can be ported to any target platform in quick time
2. Supports all function codes as per the specification
3. Supports pass through APIs for developing customer specific function codes
4. Supports RTU, ASCII and TCP variants

Why Utthunga for implementing Modbus protocol stack?

Utthunga’s Modbus stack is running in tens of thousands of systems worldwide. The stack is high performance and low-footprint. We have implemented the stack on desktop, mobile as well as embedded systems of various types. We support all the variants of Modbus, and the stack can be easily integrated into any existing module/system.