Senior/Staff Firmware Engineer - Battery Charger

About 1X

We’re an AI and robotics company based in Palo Alto, California, on a mission to build a truly

abundant society through general‑purpose robots capable of performing any kind of work

autonomously.

We believe that to truly understand the world and grow in intelligence, humanoid robots must live

and learn alongside us. That’s why we’re focused on developing friendly home robots designed to

integrate seamlessly into everyday life.

We’re looking for curious, driven, and passionate people who want to help shape the future of

robotics and AI. If this mission excites you, we’d be thrilled to hear from you and explore how you

might contribute to our journey.

Role Overview

We are looking for a cross-functional Firmware / Embedded Engineer to develop and maintain
the firmware for the battery charging system of a production humanoid robot. In this role, you
will own the embedded software that controls AC-DC power conversion, charge profile
management, and the interface between the charger and the battery management system.

You will work closely with hardware architects, electrical engineers, systems engineers, and test
engineers to ensure firmware reliably bridges hardware capabilities and higher-level system
requirements across prototype and production platforms.

The charger is a consumer-facing subsystem that must meet regulatory emissions
requirements, operate safely in household environments, and manage the charge cycle for a
high-energy lithium-ion pack that experiences demanding discharge profiles between charges.
Charging behavior directly affects battery longevity, system availability, and user safety. The
ideal candidate understands power conversion from magnetics and control loop fundamentals,
writes firmware that is robust under component variation and fault conditions, and can reason
about the interactions between charger behavior, battery chemistry, and EMC performance.

Responsibilities

• Develop and maintain charger firmware controlling AC-DC power conversion stages,
  including power factor correction and isolated DC-DC conversion topologies

• Implement charge profile management for multi-series lithium-ion packs: constant-
  current, constant-voltage, and taper phases with cell-chemistry-appropriate voltage and
  current limits

• Architect the charger-to-BMS communication interface over CAN or similar embedded
  bus, coordinating charge current requests, pack voltage feedback, temperature limits,
  and fault signaling between the two subsystems

• Responsible for the testing, validation, and verification of initial firmware releases to
  ensure functionality, reliability, and performance requirements are met

• Implement power converter control loops in firmware: voltage regulation, current
  regulation, and soft-start sequencing with stability under varying line and load conditions

• Develop fault detection and protection firmware: input overvoltage/undervoltage, output
  overcurrent, overtemperature, ground fault, and loss-of-communication with the BMS,
  each with defined safe-state transitions

• Support EMC compliance by understanding how firmware-controlled switching
  frequencies, gate drive timing, and measurement sampling interact with conducted and
  radiated emissions performance

• Collaborate with hardware architects to define charger hardware requirements, converter
  topology trade-offs, and the boundary between hardware protection and firmware
  protection

• Implement production test modes and end-of-line validation routines for charger
  acceptance, including efficiency measurement, regulation accuracy, and protection trip-
  point verification

• Develop diagnostic logging and telemetry for charge cycle data, fault history, and
  component health trending

• Document firmware architecture, interfaces, and assumptions; improve code structure,
  readability, and maintainability
  

Requirements

• Bachelor’s or Master’s degree in Electrical Engineering, Computer Engineering, or a
  related field

• 7+ years of industry experience with embedded systems and real-time firmware
  development

• Proficiency in C and C++ for embedded targets

• Production charger or power converter firmware experience — the candidate has
  developed or substantially modified firmware controlling an AC-DC or DC-DC power
  converter in a shipped product. Experience should include closed-loop regulation,
  protection logic, and charge profile implementation, not solely integration of a digital
  power controller evaluation board.

• Power conversion fundamentals — working understanding of switched-mode power
  supply operation: common AC-DC topologies (flyback, LLC, phase-shifted full bridge),
  power factor correction stages, transformer isolation, and how firmware-controlled
  parameters (switching frequency, duty cycle, phase shift) affect converter behavior

• Battery charging knowledge — understanding of lithium-ion charge protocols (CC-CV,
  multi-stage), the relationship between charge rate and cell degradation, and how
  temperature and cell age affect charge termination criteria

• Embedded bus fluency — hands-on CAN implementation for charger-to-BMS
  coordination, plus additional embedded interfaces (SPI, I²C, UART) for communication
  with power controller ICs, monitoring devices, and auxiliary circuits

• Hardware debug at the firmware boundary — experience using oscilloscopes, current
  probes, and power analyzers to diagnose problems that span firmware control behavior,
  converter waveform quality, and thermal performance

• Schematic literacy — ability to read power stage schematics (switching FETs, gate
  drivers, magnetics, snubbers, feedback networks) and understand how firmware
  interacts with the physical circuit

• Comfortable debugging firmware on real hardware using standard lab tools

• Ability to collaborate closely across hardware, systems, and software teams
  

Preferred Qualifications

• First-principles problem solving — a track record of approaching power conversion
  and charging problems from circuit and control theory fundamentals rather than relying
  solely on vendor reference designs or digital power controller auto-tuning tools

• EMC and regulatory compliance — direct experience with charger or power supply
  products that required FCC Class B, CE, or equivalent emissions certification.
  Understanding of how firmware decisions (switching frequency selection, spread-
  spectrum modulation, burst mode behavior) affect compliance test results.

• EV charging or high-power battery chargers — experience at automotive charger
  suppliers, EVSE manufacturers, or industrial battery charger companies where charge
  power exceeds 500W and regulatory, thermal, and reliability requirements are
  demanding

• Consumer electronics power systems — experience with UL/IEC 62368-1, IEC 61000
  series, or similar consumer safety and EMC standards, where the charger must operate
  safely in a household environment with untrained users

• Power factor correction firmware — implementation of active PFC control loops
  (boost, bridgeless, totem-pole) in firmware, including transient response tuning and THD
  optimization

• Digital power control — experience implementing compensator algorithms (PID, type-
  II/III) in firmware for voltage and current mode control of switched-mode converters,
  including discrete-time loop design and stability analysis

• Thermal management firmware — experience with firmware-controlled thermal
  derating, fan speed management, or power limiting based on real-time temperature
  monitoring of power stage components

• Experience contributing to hardware architecture or system-level design decisions

• Familiarity with real-time operating systems (FreeRTOS, SafeRTOS, or similar)

• Experience supporting hardware through prototype and production phases

Benefits & Compensation

• Salary Range: $175,000 - $250,000 + Equity

• Health, dental, and vision insurance

• 401(k) with company match

• Paid time off and holidays

Equal Opportunity Employer

1X is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, gender, gender identity or expression, sexual orientation, national origin, ancestry, citizenship, age, marital status, medical condition, genetic information, disability, military or veteran status, or any other characteristic protected under applicable federal, state, or local law.