Principal Firmware/Software Engineer

Please note that we are unable to provide visa sponsorship for this position. About Proper Voltage Proper Voltage is unlocking the next generation of battery technology across robotics, data centers, and defense. We're building intelligent battery systems that make advanced chemistries (sodium-ion, lithium-titanate, lithium-silicon) work in products that were never designed for them. Humanoid robots can upgrade power systems without redesigning their entire platform. Data centers get safer, cheaper backup power. Drones and autonomous vehicles get higher energy density without lengthy integration cycles. If you want to work on hard engineering problems that matter this is the place. Job Overview We are looking for a Principal Firmware/Software Engineer to lead the technical direction of firmware running on real hardware in safety-critical environments. In this role, you will architect and drive development of firmware for our battery management systems on STM32 microcontrollers, owning core BMS functions, communication architecture, safety patterns, and the platform decisions that shape multiple products across our portfolio. You will set technical direction across firmware initiatives, mentor lead and senior engineers, and partner closely with hardware, systems, and certification teams to bring complex products from concept through UL-certified production. This is a senior individual contributor role within a fast-moving, multi-disciplinary engineering team — the IC-track counterpart to our Firmware Manager. What You'll Do Architect and own the technical direction of BMS firmware on STM32 platforms (Cortex-M33/M7/M4) in C, targeting safety-critical battery applications across sodium-ion, lithium-titanate, and lithium-ion chemistries. Define the firmware platform — RTOS choice, driver architecture, layering between peripherals and application logic, safety patterns, and the shared codebase that underpins multiple products. Lead cross-product technical decisions: peripheral abstraction strategy, CAN protocol structure, fault-response architecture, and the trade-offs between portability and per-product optimization. Design and review implementation of cell voltage and temperature monitoring, over/under-voltage and over-current protection, thermal management, and passive cell balancing strategies for multi-series pack configurations. Drive functional-safety architecture: derive firmware requirements from FMEA and fault-tree analysis, define safety patterns for UL 1973 certification, and own the firmware's certification narrative. Lead bring-up of new platforms: define the bring-up sequence, drive verification of peripheral subsystems, and resolve cross-discipline issues between firmware, hardware, and analog signal chains. Mentor lead, senior, and junior engineers — through code reviews, design reviews, and direct technical coaching — and grow the firmware team's collective depth. Set standards for firmware development practices: testing strategy, CI, code review norms, documentation, and tooling. Drive continuous improvement across the team. Represent firmware in cross-functional architecture reviews with hardware, systems, T&D, and product teams. Provide authoritative firmware-side input on schematics, signal routing, component selection, and product architecture. Author and own platform-level firmware documentation: architecture decisions, interface specifications, safety analyses, and reference designs that other engineers build from. Ability to either work in person at our Carlsbad, CA office or travel there as needed with a demonstrated track record of highly efficient, collaborative remote work. Required Qualifications B.S. or M.S. in Computer Engineering, Electrical Engineering, Computer Science, or related field (advanced degree preferred). 8+ years of experience developing embedded firmware in C for ARM Cortex-M microcontrollers, with at least 2+ years in a senior or principal-level role setting technical direction. Demonstrated track record of architecting embedded firmware platforms — not just feature implementation. You can point to a system you designed, the trade-offs you made, and how it shipped. Deep hands‑on experience with STM32 peripherals: ADC, SPI, I2C, UART, CAN, DMA, GPIO, and timers, including the analog‑signal‑chain implications of each. Strong RTOS expertise (FreeRTOS, Zephyr, or equivalent), including task design, scheduling, priority/inversion analysis, and the failure modes RTOSes introduce. Experience taking firmware through safety certification (UL 1973, UL 9540, IEC 62619, ISO 26262, IEC 61508, or analogous standards). Experience defining and enforcing safety‑critical firmware practices: MISRA‑style coding standards, fault‑response design, watchdog architecture, and recoverable‑vs‑fatal fault classification. Mature understanding of analog signal chains, ADC sampling, filtering, calibration, and noise — and how firmware decisions ripple through them. Strong CAN bus architecture experience: protocol design, message framing, fault handling, and bus‑level diagnostics. Demonstrated mentorship and technical leadership — you've raised the bar of the engineers around you, formally or informally. Proficient with embedded debug workflows (JTAG/SWD, logic analyzers, oscilloscopes) and structured development workflows (Git, code review, CI). Effective communication skills across various levels of the organization, including the ability to make technical trade‑offs legible to non‑firmware stakeholders. Proven ability to thrive in a fast‑paced startup environment, owning ambiguity and driving decisions with minimal supervision. Preferred Qualifications Experience leading firmware for a battery management system or power electronics product from concept through production and certification. Deep functional‑safety experience (ISO 26262, IEC 61508, or equivalent), including SIL/ASIL classification and safety‑case authoring. Experience with digital filtering techniques (moving average, low‑pass IIR, Kalman filters) applied to sensor data in safety‑critical contexts. Familiarity with current sensing techniques, isolated measurement circuits (e.g., AMC1301‑class isolated amplifiers), and precision ADC applications. Experience defining hardware‑in‑the‑loop testing strategy and emulation frameworks (Renode, QEMU) for embedded systems. Prior Experience With C/C++ for embedded development. Hardware‑in‑the‑loop testing and emulation frameworks (Renode, QEMU). CPLD or FPGA interfacing from a firmware perspective, including hardware/firmware partitioning decisions. Python for scripting, log analysis, and test automation. High‑voltage systems (100V+) and associated safety practices. Publishing technical work, internal or external (design docs, conference talks, papers). Equity options as part of the compensation package. Generous paid time off and paid holidays (PTO) policy. Ready to write the firmware that powers the future of energy? Let’s talk. #J-18808-Ljbffr