Senior Firmware Engineer

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 BLU

Your Role
This is a hands-on senior engineering role with real product ownership. You shape the shared firmware platform behind Shelly BLU and bring new battery-powered BLE and BLE+Zigbee devices from first project setup all the way to production — with a strong focus on low power, connectivity, security, and reliability.

Responsibilities

• You evolve the shared Shelly BLU firmware SDK and keep it reusable, versioned, maintainable, and ready to support multiple devices.
• You develop new Shelly BLU products end-to-end — from project setup and sensor integration to production-ready firmware and release.
• You optimize the complete power and state lifecycle to achieve the right balance between responsiveness, radio performance, reliability, and long battery life.
• You build and maintain the BLE functionality of our devices, including BTHome advertising, GATT services, pairing, connection management, JSON-RPC over BLE, and OTA updates.
• You own secure device identity, provisioning, encryption, signed and encrypted firmware updates, factory reset, and reliable non-volatile configuration.
• You build reproducible workflows for compiling, flashing, signing, provisioning, testing, and producing release images.
• You create host-based and device-level tests, troubleshoot complex firmware, hardware, radio, power, and production issues, and drive them through to resolution.
• You contribute to architecture and technical decisions and work closely with Hardware, QA, Product, and Manufacturing to turn ideas into reliable products at scale.

Requirements

• You bring 5+ years of experience in embedded firmware development and strong modern C skills on ARM Cortex-M class SoCs, ideally in battery-powered, connected, or ultra-low-power products.
• You are confident with RTOS-based systems and understand the full device lifecycle — timers, events, interrupts, deep sleep, retention, wake sources, watchdogs, and radio activity.
• You know how to build scalable firmware on top of a shared, versioned SDK, using reusable components, clean extension points, and device-specific configuration instead of creating separate firmware forks.
• You are fluent in BLE, including advertising, GATT servers, bonding, passkey pairing, connection lifecycle, OTA DFU, BTHome, and JSON-RPC over BLE.
• You are comfortable integrating sensors and peripherals through GPIO, PWM, ADC, UART, I2C, timers, and similar interfaces.
• You understand embedded security and persistent data design, including device identity, provisioning, encryption, signed and encrypted OTA, key lifecycle management, and non-volatile storage across firmware updates.
• You work comfortably with Make, Linux shell, code generation, cross-compilation, containerized builds, vendor flashing/signing tools, and host-based or hardware integration testing.
• Experience with Zigbee/ZCL, Python or another scripting language, embedded CI/CD, and hardware-in-the-loop automation is a strong advantage.

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.