Embedded software engineer – HVAC controls

Do you take pride in writing clean, efficient embedded code and seeing it perform reliably in real products? Here’s a position where you can apply your software skills to develop control systems that keep modern HVAC installations running smoothly.

OJ Electronics – a Danish producer of electronic controls for underfloor heating, HVAC drives, and controllers – is looking for an embedded software engineer to join our R&D team in Sønderborg, Denmark.

In this position, you’ll work on the software that powers our HVAC controllers – from microcontroller-based firmware to embedded Linux applications. Your focus will be on writing clean, well-structured code, integrating software with custom hardware, and contributing to system architecture and testing.

Reporting to our R&D manager, controls, you’ll be part of a team that values solid engineering craftsmanship and close cooperation with colleagues in hardware, testing, and production technology.

Your role

As part of the R&D team, you’ll collaborate with colleagues in hardware, cloud software, and UX to build reliable, maintainable products that meet strict quality and performance requirements.

Specifically, your role will involve:

• Developing embedded software in C/C++ for microcontroller-based and Linux-based systems
• Integrating software with custom hardware
• Maintaining code quality through testing, refactoring, and code reviews
• Contributing to system design and software architecture
• Implementing user interfaces in React for selected web-based applications
• Supporting the Yocto build pipeline for embedded Linux
•  

Working at OJ At OJ Electronics, you’ll find an informal, open and collaborative culture where people take pride in doing quality work.

We offer:

• A flat organisational structure where decisions are made quickly
• Opportunities to grow your expertise and responsibility over time
• A healthy work-life balance and flexible working hours (30–37 hours per week)
• Competitive salary and pension package
• A modern workplace with canteen and good facilities

Employee satisfaction has consistently remained above 80 for several years – and we take pride in maintaining a workplace where people truly thrive.

Please note that this position is based in Sønderborg, Denmark, and requires your physical presence on site. This is not a hybrid or remote position.

The application process For this position, we will be interviewing on an ongoing basis until we find the right person.

About OJ Electronics

Founded in 1964 and headquartered in Sønderborg, Denmark, OJ Electronics produces electronic controls for underfloor heating and HVAC controls and drives. Our products are available through partners and distributors worldwide, and we have subsidiaries and sales offices in key markets, including the United States and Poland. Everywhere, we are known for our innovative approach, insistence on product quality, and deep application knowledge – all of which helps customers differentiate themselves in the market.

In June 2023, OJ Electronics was acquired by BITZER Electronics, a BITZER Group company also headquartered in Sønderborg. This makes OJ Electronics part of the BITZER Group family, which is represented at 75 locations in over 40 countries and employs some 4500 people worldwide, including about 175 at OJ Electronics.

Must-have qualifications

• Bachelor’s degree or higher in embedded software, electronics engineering, or similar
• At least three years of experience in embedded software development
• Proficiency in C/C++ for embedded systems
• Experience with embedded toolchains (GCC, ARM toolchain, or similar)
• Experience with real-time programming and microcontrollers
• Familiarity with embedded debugging tools
• Understanding of hardware/software interfaces and schematics
• Experience with version control (Git + Git Flow) and CI/CD
• Knowledge of communication protocols such as UART, I2C, SPI and Ethernet (TCP/IP)
• Structured problem-solving skills and clear technical communication in English

Nice-to-have qualifications

• Experience with Fieldbus protocols (Modbus, BACnet)
• Experience with embedded displays (TFT, LCD)
• Knowledge of wireless protocols (Wi-Fi, BLE)
• Familiarity with IoT and embedded-system security principles
• Experience with unit testing frameworks for embedded systems or hardware-in-the-loop testing
• Understanding of cloud-connected embedded systems or IoT communication (MQTT, REST)