Johnson Controls

Principal Firmware Engineer

Belfast-County Antrim-United Kingdom Full time

What you will do

As a Principal/Senior Firmware Engineer, you will aid in the design, development, and maintenance of embedded firmware across a range of CEM Systems hardware platforms. You will work closely with hardware, software, and systems teams to deliver reliable, secure, and high-performance solutions used globally in critical infrastructure, airports, data centres, and enterprise environments. This is a hands-on technical position involving firmware design, secure solution development, problem-solving, and full product lifecycle support.

How you will do it

Embedded Firmware Development

  • Design,  implement and support firmware for embedded systems using RTOS-based environments.
  • Develop/maintain/debug multi threaded firmware applications using signals, semaphores, mailboxes, and other RTOS primitives to manage constrained resources.
  • Create clear, robust finite state machine logic for deterministic device behaviour.
  • Implement internal communication protocols including SPI, I²C, and other MCU subsystems.
  • Design for Security – develop firmware with latest cyber security practices at the core

Networking & Security Protocols

  • Develop and maintain embedded networking features using the ISO model, including TCP/IP, routing, subnets, client/server operation.
  • Integrate secure communication technologies including TLS (MBED, WolfSSL) and modern cipher suites such as AES, CHACHA20 along with SHA.
  • Work with access-control-specific communication standards, including OSDP for control panels and peripheral devices.

Smart Card & RFID Technologies

  • Implement and support smart-card reader technologies across ISO 14443A/B, ISO 15693, and related RFID standards.
  • Work with DESFire architecture, including AES and 3DES encryption modes, application identifiers (AIDs), and file structures.
  • Support legacy and proprietary card formats including MIFARE Classic, HID iClass, and customer-specific technologies.

Electronics & Hardware Interaction

  • Read, interpret, and collaborate using circuit diagrams and system schematics.
  • Understand power supply behaviour, electrical limitations, and protection considerations.
  • Work with RS485 asynchronous communications, Ethernet hardware, NFC antenna systems, relays, and FET-based output drivers.

Problem Solving & Technical Leadership

  • Conduct root-cause analysis across multi-component systems—both hardware and firmware.
  • Develop solutions that minimise collateral impact and maintain system stability.
  • Mentor junior engineers, perform code reviews, and contribute to engineering best practice.

What we look for

Essential

  • Proven experience designing firmware for embedded systems (ideally real-time / resource-constrained environments).
  • Strong proficiency in C, familiarity with C++ and JAVA is desirable.
  • Experience with a range od IDEs including Keil uVision, QT Creator, Android Studio and source control systems including Github and TFS
  • Experience with embedded Linux and Android operating systems desirable along with
  • Solid understanding of hardware fundamentals and microcontroller architectures.
  • Demonstrable experience with networking stacks and secure communication protocols.
  • Experience with smart-card or RFID technologies is a significant advantage.
  • Excellent analytical and debugging abilities, including use of oscilloscopes, logic analysers, and protocol tools.
  • Ability to work autonomously and collaboratively across multidisciplinary teams.
  • Familiarity with Mitsubishi PLCs desirable.

Desirable Experience

  • Experience in access control, security systems, or other safety-critical embedded environments.
  • Previous leadership/mentoring responsibilities.
  • Familiarity with compliance, certification, or regulated environments.

What we offer

  • Work on innovative, industry-leading security products used worldwide.
  • Join an experienced engineering team with strong technical depth.
  • Opportunities for technical leadership, architecture influence, and career progression.
  • Competitive salary, benefits, and flexible working options.

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