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About Castelion

Castelion is bringing a new approach to defense development and production: one that focuses on short, iterative design cycles, rapid flight testing in development, and modern commercial manufacturing strategies for production at scale. We're designing, building, and testing next generation long range strike weapons systems to give America and its Allies a definitive edge and deter future conflicts.

Senior Embedded Software Engineer

Castelion is seeking a Senior Embedded Software Engineer to architect, implement, and harden software running on resource constrained, mission critical systems. You'll write low-level C and Rust, accelerate workloads with CUDA, and own secure processing paths (crypto, secure boot, key management) from concept through field test. You'll collaborate closely with electrical, systems, and test teams to bring new hardware online fast and keep it reliable.

Responsibilities

Embedded & Firmware Development

• Design and implement embedded applications, device drivers, and board support packages in C and Rust.

• Optimize and parallelize compute-intensive algorithms using CUDA on embedded GPUs.

• Bring up new boards: bootloaders, secure boot chains, peripheral initialization, and diagnostics.

• Implement and validate cryptographic protection using TPMs

Systems Integration & Testing

• Integrate sensors, comms links, and high-rate data paths, profile and tune for latency and throughput.

• Develop automated HW-in-the-loop tests; script board flashing, provisioning, and regression suites.

• Use JTAG, logic analyzers, oscilloscopes, and trace tools to debug hard problems.

Monitoring & Telemetry

• Instrument systems for performance and reliability; feed data to Grafana/Foxglove for analysis.

Collaboration & Troubleshooting

• Partner with cross functional teams to isolate issues quickly in lab and field environments.

• Document designs, decisions, and interfaces clearly for internal and external stakeholders.

Basic Requirements

• Bachelors in Computer Science, Electrical/Computer Engineering, or related field.

• 5+ years professional embedded software experience (bare metal and/or RTOS).

• Strong proficiency in C and production Rust (unsafe code discipline, ownership semantics).

• Hands-on CUDA development on embedded or edge-class GPUs (Jetson, similar).

• Experience with ARM-based SoCs, memory-mapped I/O, DMA, interrupts, IPC.

• Proven work on secure boot, cryptography libraries, key management, or similar security-critical code.

• Comfortable with Linux internals, cross-compilers, build systems, and hardware debugging tools.

• Solid Git/GitHub workflows and familiarity with modern CI/CD.

Preferred Skills and Experience

• Experience with Zephyr, FreeRTOS, or seL4;

• Knowledge of DSP, real-time networking, or RF signal chains.

• Azure or other cloud services for telemetry ingestion.

• US Citizenship and ability to potentially obtain/maintain security clearance.

Leadership Qualities

Bias to Action and Creative Problem Solving. Desire and experience questioning assumptions in ways that lead to break through ideas that are ultimately implemented. Successfully bring in applicable processes/concepts/materials from other industries to achieve efficiency gains. The ability to personally resolve minor issues in development without requiring significant support.

High Commitment, High Initiative. A successful candidate will have a genuine passion for Castelions mission and consistently look for ways to contribute to the company's technical goals and prevent hardware blockers. Ability to work in a fast paced, autonomously driven, and demanding atmosphere. Strong sense of accountability and integrity.

Clear Communicator. Proactively communicates blockers. Trusted in previous roles to be voice of company with regulators, suppliers, gate keepers and customers. Capable of tactfully managing relationships with stakeholders to achieve company-desired outcomes without compromising relationships. Emails, IMs and verbal interactions are logical, drive clarity, and detailed enough to eliminate ambiguity.

All employees are granted long-term stock incentives as part of their employment as Castelion. All employees receive access to comprehensive medical, vision, and dental insurance, and the company offers four weeks of paid time off per year.

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.

While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S. government–issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.