The challenge

A manufacturer of ultrasonic welding systems faced a clear task: the controller of a new device version had to support PROFINET. In the previous model, parameterization was handled via a serial interface. An STM32 microcontroller controlled frequency, amplitude, and other parameters.

For the new product generation, the end customer required real-time-capable PROFINET communication. The new interface also needed to integrate seamlessly into the existing architecture. At the same time, the required effort had to be kept to a minimum – especially with regard to hardware modifications and certification.

The requirements

The project constraints set clear priorities for the machine builder: time, engineering resources, and production volumes were limited.
The PROFINET interface needed to fit into the existing system architecture. The machine builder’s team did not want to initiate a major hardware redesign. Certification also had to remain lean, so the scope was deliberately reduced to the essentials.

The project was managed by Brückmann Elektronik as the system developer on behalf of the machine builder as end customer. Since Brückmann had limited PROFINET experience, the company brought in Burger Engineering, a systems engineering specialist, for support. Burger’s team has been an officially certified Hilscher “netX Design-In Partner” for several years and therefore offers extensive hands-on expertise in integrating industrial communication using Hilscher products.

A key element was selecting the right communication module. The decision was quickly made in favor of Hilscher’s netRAPID 90.

The netRAPID 90 is a compact communication module with an integrated netX 90 chip. It is supplied to Brückmann and its customers with the PROFINET communication stack preloaded. Other communication protocols such as EtherCAT and EtherNet/IP, as well as fieldbuses like PROFIBUS or DeviceNet, are also available. The module can be integrated into existing designs without extensive hardware development.

Product highlights of Hilscher’s netRAPID 90:

• Solder-ready netX 90 design
• SPI interface to the host
• Multi-protocol design with pins for Industrial Ethernet and fieldbus
• Integrated Cortex-M4 processor for application tasks

The Brückmann and Burger teams also discussed numerous alternatives, including integrating the netX 90 directly into the device. In the end, they quickly ruled out a separate PCB development with a design-in of Hilscher’s multiprotocol processor – the expected production volumes were too low, and the effort would have been disproportionate.
With its compact form factor, a complete communication and application unit, and available development and certification tools, the netRAPID 90 proved to be the most efficient solution.

Phase 1: Implementation — February to June 2023

• Definition of the technical framework
• Selection of the netRAPID 90 as the most suitable solution
• Implementation of the application and initial development using evaluation boards

Phase 2: Optimization and certification

• Preparing the solution for official PROFINET certification
• Certification
• Reducing the solution to the required feature set

Implementation

Separating application and communication

The core of the technical solution was a clear separation between application logic and communication logic. The existing STM32 controller already covered all device-specific functions, including frequency control, amplitude control, and power management. For this reason, it was not intended to take on additional PROFINET tasks.

Initially, the team planned to operate the netRAPID 90 in companion mode. In this approach, the application remains on the STM32, while the netRAPID 90 handles the connection to the PROFINET network.

However, because the STM32 was already running at the limits of its performance due to time-critical sequences, the team opted for stand-alone mode instead. This allowed the second core of the netX 90 to exchange application data via PROFINET between provider and consumer. As a result, PROFINET communication was implemented with virtually no additional performance impact on the STM32.