Firmware Developer

Job description

We make smart devices and push the boundaries of the IoT sector every single day. Shelly is a strong company with a startup mindset - no bureaucracy, just bold ideas, creative problem-solving, and a team that genuinely loves what they do.

We turn every spark of an idea into a real product — from first concept to full production - and bring smart automation to over 3 million households around the world. From heating, lighting, appliances, curtains, and more - if it runs on electricity, chances are we can automate it. We’ve built over 100 smart devices (and counting!), and everything happens right here at our headquarters in Sofia.

Sounds exciting? Keep reading...

Senior Firmware Engineer — Shelly X Platform

Your Role

You design, implement, and evolve the architecture of the Shelly X firmware platform — the shared firmware chassis that turns generic hardware into branded OEM products through signed, declarative product definitions. You build platform capabilities that stay reusable across product generations while ensuring secure provisioning, long-term compatibility, and maintainable system architecture. This is a hands-on senior individual contributor role focused on platform and systems engineering, not people management, board bring-up, or application/UI development.

Job requirements

• You bring strong senior-level experience designing and shipping embedded firmware platforms where architecture and hands-on implementation go hand in hand.
• You model device behavior through declarative, data-driven configuration instead of product-specific firmware and maintain a clear separation between platform and product concerns.
• You design versioned schemas and configuration models with explicit forward and backward compatibility across firmware upgrades and downgrades.
• You approach device identity, provisioning, cryptographic trust, firmware signing, and lifecycle lockdown as one coherent system.
• You write modern C++ for resource-constrained embedded environments and understand the trade-offs between performance, memory usage, reliability, and maintainability.
• You work confidently with RTOS concepts, multitasking, synchronization primitives, interrupts, and low-level execution contexts.
• You have strong peripheral-level knowledge, including GPIO, PWM, RMT, UART, ADC, and DMA.
• You understand networking fundamentals across the IP stack and common application protocols.
• You have hands-on experience with applied cryptography for embedded systems, including JWS/JWT (RFC 7515/7519), ECDSA P-256/P-384, mbedTLS, code-signing lifecycles, and firmware image signature verification.
• You design layered and plugin-based architectures using registries, factory dispatch, link-time component binding, and runtime instantiation from declarative sources.
• You understand multi-chip firmware architectures and serial co-processor integration, including RS-485/Modbus RTU, proprietary MCU protocols, and OTA updates for secondary MCUs.
• You build reproducible development environments using Make, Python-based code generation, Docker, dependency pinning, and declarative YAML/JSON schemas.
• You use Linux comfortably for development, shell tooling, cross-compilation, and containerized build environments.
• You use scripting languages, such as Python, to build tooling, automate workflows, and support analysis.
• You treat unit testing and host/Linux simulation-based CI as first-class validation tools and design software with testability in mind.
• You enjoy solving complex systems problems, challenge assumptions, and communicate architectural decisions clearly.

Job responsibilities

• You define and evolve the architecture of the Shelly X firmware platform while keeping it scalable, maintainable, and reusable across multiple OEM products.
• You implement core platform functionality in modern C++ and maintain high standards for quality, performance, and reliability.
• You design declarative configuration models that allow products to be defined through trusted data instead of custom firmware builds.
• You build and maintain secure provisioning, identity, signing, and firmware trust mechanisms throughout the product lifecycle.
• You design versioning and migration strategies that preserve compatibility across firmware updates and rollbacks.
• You develop layered platform components that support runtime instantiation, extensibility, and long-term maintainability.
• You integrate and maintain communication between primary and secondary MCUs, including secure update mechanisms where required.
• You improve the build system, tooling, and code-generation pipeline to ensure reproducible and efficient development workflows.
• You write clean, well-tested code and expand automated validation through unit tests and Linux-based simulation environments.
• You collaborate closely with firmware, hardware, security, and product teams to turn platform requirements into robust technical solutions.
• You document architectural decisions, technical designs, and platform conventions that support long-term development.
• You continuously improve the platform by identifying opportunities to simplify complexity, increase reuse, and strengthen security.

Job benefits

Work:

• A welcoming, collaborative team• Meaningful products and services that people actually use and love.
• Learning opportunities to sharpen your skills
• Competitive salary + Performance bonuses
• Modern office in a great location
• Fun team buildings and company events

Lifestyle:

• 26 days of paid annual leave
• Flexible working hours
• Additional health insurance
• Free access to all Shelly devices (yes, you can smarten up your whole home!)
• Multisport Card
• Fully sponsored yearly public transport card

Ready to join the Shelly Revolution?

Let’s build the future of smart living together.
Hit that Apply button — we can’t wait to meet you.