Junior Embedded Engineer (RTOS)

Lumai's hardware needs software that runs reliably at the very bottom of the stack. The accelerator is moving from prototype toward production and the embedded team is small, so the firmware, drivers and RTOS control work underneath sits on the critical path. This is a junior hire into a team where bring-up is a shared, hands-on job.

You will build the firmware, drivers and RTOS-based control software that bring the accelerator up and keep it deterministic. That means RTOS tasks and inter-process communication for the management software, board support package bring-up from peripheral drivers and boot loaders through to first-boot debugging, and the unit and integration tests that keep it that way. You will work alongside the senior embedded engineer and the hardware teams, and you will document what you find for the people who come after you.

What is genuinely hard about this is that the title is junior but the work is not: when a board will not boot you are reading a serial console, a scope and a debugger on custom hardware, where the answer is often that the hardware and the code disagree and nobody has seen the failure before. There is no reference design to lean on.

By month six, you will have taken your modules through unit test and CI, supported bring-up on at least one hardware revision, and documented interfaces, register maps and bring-up procedures that the team actually uses.

• Implement and integrate RTOS tasks and inter-process communication for the accelerator management software.

• Contribute to board support package bring-up: validate peripheral drivers, configure boot loaders and support first-boot debugging.

• Write unit and integration tests for firmware modules and maintain the embedded CI pipelines.

• Support hardware debug sessions with JTAG, GDB and benchtop instrumentation.

• Document firmware interfaces, register maps and bring-up procedures for internal use.

• Work with the senior embedded engineer and the hardware teams on new hardware revision planning.

Must-have

• Three or more years of embedded C/C++ experience in a hardware product environment (a degree in electrical engineering, computer engineering or equivalent).

• Working knowledge of at least one RTOS - FreeRTOS, Zephyr or similar - in a production context.

• Experience with board support package or board bring-up activities, including boot loader configuration.

• Comfort with hardware debugging tools: JTAG, oscilloscopes and serial consoles.

• Familiarity with Linux kernel concepts and basic driver development.

Strong preference for

• Experience with DMA controllers or cache coherency management.

• A background in safety-critical or automotive embedded software (MISRA C, ISO 26262).

• Exposure to Python-based test automation for hardware-in-the-loop testing.

Lumai is the optical compute company building the next generation of AI infrastructure. Spun out of optics research at the University of Oxford in 2021, we compute with light instead of electrons. Our 3D optical technology carries out the matrix multiplications at the heart of AI inside beams of light travelling through free space, which lets it go beyond the limits of both silicon GPUs and integrated photonics.

In April 2026 we launched Iris Nova, the world's first optical computing system to run billion-parameter large language models in real time, using up to 90% less energy than conventional GPU-based systems. Iris Nova, the first server in the family, is now available for evaluation by hyperscalers, neoclouds, enterprises and research institutions. Aura and Tetra will follow.

Our work won the Falling Walls Award for Science Breakthrough of the Year 2025 and 'Best Overall Technology' at the OCP Future Technologies Symposium. We are headquartered in Oxford.

You'll work on a new kind of computer. Optical computing for AI has been promised for decades. We have a working system running real models, and the hard part left is taking it to volume.

Your work ships. We are moving from first product to volume production, so what you build this year goes into the servers our customers run.

You'll work across disciplines. Optical engineers, machine learning researchers, and hardware and software engineers solve problems together. You will learn things that don't appear on your job description.

The work matters beyond Lumai. AI's appetite for energy is one of the defining constraints of the next decade. Our mission is sustainable intelligence at global scale: AI that is faster, cheaper to run and far less power-hungry.

You'll join early. You'll have a real say in how we build the product, the team and the way we work.

Lumai is an equal opportunity employer. We make hiring decisions based on skills, experience and potential, and we welcome applications from people of all backgrounds. If you need an adjustment at any stage of the hiring process, let us know and we will do our best to support you.