Industrial communication protocols and the Internet of Things form a real alphabet soup: IIoT, OPC UA, MQTT, HTTP, REST, CoAP, MODBUS, DDS, (…), to infinity and beyond. The technical feasibility of inserting these solutions in the industry has also been widely explored. Now we are facing a phase where figuring out how to optimize processes through this alphabet soup – the industrial protocols – is the difference. In this article, we will briefly introduce industrial protocols and the IoT scenario.
What are Industrial Communication Protocols?
A communication protocol is a set of rules that electronic devices must follow to allow information to be exchanged with one another. On a shop floor, for example, devices based on different languages are employed but, being part of the same production line, need information from other equipment. Industrial protocols allow this information to be transmitted and processed properly within the industrial production line.
Engineers and integrators involved in the industry are often asked what is the best technology for a business and how integration between different applications should be done. The diversity of existing communication protocols leaves doubts on the way forward. In this scenario, understanding industrial communication standards allows you to optimize the performance of a solution. However, how can we determine which protocols optimize an industrial solution?
We will hardly have a standard open protocol that meets all scenarios. Legacy equipment, varying requirements in different industries, and people with different skills do not allow you to consolidate the solution into a universal standard. It is important to do your homework and use the correct protocol to arrive at a project solution.
This architecture requires devices to connect to and publish data mediated by broker topics. A device that reads a sensor can publish this information to a topic and others can subscribe to it to receive this information automatically. This model decouples the sensor devices and clients.
Differences between the types of architecture
When it comes to advantages and disadvantages, the client/server architecture enables greater interoperability and security as it is made up of peer-to-peer connections. However, these connections are not very scalable due to the need for connection management and use of computational resources.
The publish/subscribe architecture, on the other hand, allows for greater scalability because it decouples consumer sensors, which can be inserted or removed independently. Ensuring security, in this case, is more complex as there are more points involved and connected. There are also interoperability issues from the moment a data generator changes the message format, forcing all consumers to make the same change.
The protocols outlined below have the potential to connect industrial devices to the IoT platform. Now that we have an idea of communication architectures, let’s go into more detail of industrial protocols:
OPC (Open Platform Communications Unified Architecture) is the new generation of the standard created by the OPC Foundation. The classic OPC protocol is already known in the industry for providing a standard communication interface with PLCs (Programmable Logic Controllers). The new generation extends interoperability between devices and enables information traffic to the management layer of the enterprise.
OPC UA is a client/server protocol where the client connects, reads writes, and browses industrial equipment. It is highly secure, allows encryption and supports interoperability between different manufacturers. It is a widely used solution in the industry, as it allows the connection between PLCs and sensors in the Supervisory Control and Data Acquisition (SCADA) system and the Manufacturing Execution System (MES). However, OPC UA is new to enterprise IT, and its use is intimidating due to its complexity when compared to other protocols. To circumvent this problem, the OPC Foundation has made public the OPC UA standard in an attempt to increase its adoption in industries.
HTTP (REST / JSON)
Hypertext Transfer Protocol (HTTP) works in the client/server style and is ubiquitous on the web. It is very accessible since any programming language has libraries of this type. The importance of HTTP in IoT is related to the REST model, which allows access to data and resources through requests.
The use of HTTP in the industry is mostly used for equipment configuration, but not for sending data. IoT devices allow data traffic over HTTP, contrary to the industry. However, this scenario is changing as there are numerous gateways and PLCs that have now added native support for data via HTTP.
MQTT (Message Queuing Telemetry Transport) is a publish/subscribe protocol designed for SCADA and remote networks. It has a few byte header and robust communication. Like HTTP, MQTT allows any data to travel across your network, although JSON and binary data are the most commonly used. MQTT is not widely used as HTTP but is growing a lot in the area of IoT. Most programming languages already support MQTT, and most IoT platforms already insert MQTT as their input protocol.
The most diverse IoT communication protocols have room in the industry. It is difficult to measure which protocols are most used, but all of them have pros and cons. The important thing is to use an architecture that meets application needs and ensure that industry partners support and can adapt to this scenario. This will guarantee the success of the project and avoid competition between communication protocols.