Junior Embedded Engineer; RTOS

The Opportunity

Lumai is redefining how the world computes. We are an ambitious, venture-backed UK startup pioneering a breakthrough AI accelerator for data centers which uses 3D optical compute. Our radical technology uses light to perform computation at orders of magnitude faster speeds and at far greater scales than ever before, all whilst consuming far less energy than traditional approaches.

Lumai is unlocking performance and efficiency gains that could transform the economics of AI and compute infrastructure and reshape how intelligence scales globally.

If you are passionate about bringing groundbreaking technology to market, and want to be part of a team pushing the boundaries of what is physically possible, Lumai is where you can make it happen.

Founded in 2022, Lumai is a University of Oxford spinout using optical processing to accelerate large language models (LLMs) and other transformer-based AI systems. The team combines expertise in optical computing, machine learning, and physics.

Lumai has already secured over $15 million in investment from leading deep-tech investors like Constructor Capital, IP Group, Photon Ventures and government grants, and is scaling rapidly to deploy the fastest optical compute currently available globally.

Lumai's hardware needs software that runs reliably at the lowest levels of the stack. As our Junior Embedded Engineer, you will build the firmware, drivers, and RTOS-based control software that bring our AI accelerator to life — from initial power-on through to stable, performant operation in production systems.

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

• Contribute to BSP bring-up activities: validating peripheral drivers, configuring boot loaders, and supporting first-boot debugging sessions

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

• Support hardware debug sessions using JTAG, GDB, and benchtop instrumentation

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

• Collaborate with the Senior Embedded Engineer and HW teams on new hardware revision planning

Must-Have

• 3+ years of embedded C/C++ experience in a hardware product environment

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

• Experience with BSP or board bring-up activities, including boot loader configuration

• Comfort with hardware debugging tools (JTAG, oscilloscopes, serial consoles)

• Familiarity with Linux kernel concepts and basic driver development

• Bachelor's degree or higher in Electrical Engineering, Computer Engineering, or equivalent

Strong Preference For

• Experience with DMA controllers or cache coherency management

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

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

• Highly Competitive Salary: We are not saying our salary is a blank check, but let's just say it won't be a source of your stress

• Share Option Scheme: We are all in this together! We believe in shared success while we build the Lumai of tomorrow

• Pension Scheme: Plan for retirement with AVIVA

• Private Health Insurance: We firmly believe that you come first, and a happy you is a healthy you! Look after yourself and your loved ones with AXA

• Cycle to Work: Spread the cost of a bike, a bike and accessories or just accessories and save on tax

• L&D Allowance: Stay at the forefront of your field with a £500 annual development budget

• Subsidised On-site Lunches: Enjoy on-site healthy meals at half the price, as Lumai covers 50% of the cost

• Holidays: Enjoy some deserved "me time" with 25 days paid holiday (plus bank holidays) per year

• Socials: Be part of an inclusive community enjoying occasional all-company off-sites, lunches and socials

Our process is four stages. An initial conversation with our HR team to understand what you want from the role and what we want from it. Two technical sessions with various members of our engineering team. Finally, an HR-team session covering scope, terms, and any final questions. We aim to move fast on candidates we are excited about; expect roughly three to four weeks end to end.

Lumai is an equal opportunity employer. We make hiring decisions on merit, scope-fit, and the strength of the working relationship we expect to build with each hire. Applications welcome from candidates of any background. If you are not sure whether you are a fit, send a note anyway.