Robust Serial Communications

AutomationDirect, Cumming, GA

Figure 1. An Arduino microcontroller hardened for industrial use, such as the AutomationDirect ProductivityOpen platform, provides the networking, open-source programming, and expandability needed for users to implement serial communications, along with other control and networking applications. (Image: AutomationDirect)

Serial data transmission has served as a mainstay of digital communications since the standard was introduced in the 1960s. Variants of RS232/RS485 have been commonplace in many types of laboratory instruments, industrial devices, and other intelligent electronics. But because the newest devices commonly feature wired Ethernet or Wi-Fi capability, some may think that serial communications are simply not relevant anymore.

In reality, many scientific, commercial, and industrial electronics continue to offer proven RS232/RS485 communications because the technology is inexpensive and sufficient for a significant number of applications. This means users will continue to need robust solutions for linking RS232/RS485 devices to other host equipment for performing configuration/setup, diagnostics, and data acquisition.

For some users, especially those familiar with “homebrew” tech projects, an immediate consideration is to implement a hobby- or consumer-grade microcontroller — such as a Raspberry Pi or an Arduino — to perform the data connectivity task.

The Arduino is especially interesting for this role because of its minimalist design and low cost, with the ability to stack on “shield” boards to provide functions like wired Ethernet and Wi-Fi. However, most basic microcontrollers of this type are more suited for prototyping because they lack some essential qualities needed for creating robust installations.

A better solution is to select a microcontroller purpose-built for industrial use, combining the benefits of open-source connectivity with serial and Ethernet communications, in a form factor suitable for DIN rail mounting. One such option is the AutomationDirect ProductivityOpen Controller, consisting of a MKRZero Arduino designed into a rugged housing and certified to meet a number of industry standards, such as UL (Figure 1).

Many industrial devices, including variable frequency drives (VFDs) and loop controllers, come with built-in serial ports using the popular Modbus RTU protocol. Other laboratory and commercial devices — such as analytical instruments, machinery, barcode scanners, and lighting controllers — also come with serial ports, which may use Modbus or other protocols.

RS232 is typically used point-to-point to connect one device to a host, while RS485 can connect many devices to a host. A two-conductor shielded cable, connected between devices or daisy-chained through several devices, is economical and easy to install, even over large distances.

An example application would be a microbrewery where many temperature controllers are used, and the brewers would like to upgrade their system to historize live temperatures during batch operations and provide alarm indications. An industrial Arduino with a serial module and an Ethernet module would be ideal in this environment because it is straightforward to install RS485 between the Arduino and the temperature controllers, and to connect via Ethernet to an HMI, a higher-level network, and/or other devices or systems.

Figure 2. The ProductivityOpen industrial Arduino can be programmed using C++ code or configured with the free ProductivityBlocks graphical programming interface. (Image: AutomationDirect)

Programming could be accomplished using standard C++ code, or by using the free ProductivityBlocks graphical block diagram development environment, to quickly assemble typical functions using drag-and-drop blocks (Figure 2). The temperature data could be aggregated, scaled, and evaluated for high/low alarm values, with the results transmitted to the cloud over Ethernet using the industry-standard MQTT protocol, for example.

Devices of all types are becoming more intelligent and may include native Ethernet. However, there are many opportunities where proven serial communications will remain the best choice for cost-effective communications. An industrial Arduino platform can be the best way to integrate traditional and contemporary communications technologies, using a reliable and rugged computing platform.

This article was written by Chris Kregoski, Product Engineer, AutomationDirect (Cumming, GA). For more information visit here .