Embedded Firmware Engineer, BLE & Low-Power Wearables

Lumysi; Mexico; On-site; PHP 6,083,000 - 9,124,000; Full time

Benefits offered by this job

Firmware ownership

Direct collaboration with founders

International product exposure

Job summary

Lumysi, a US-based startup building a premium wearable health bracelet, seeks an Embedded Firmware Engineer to own the firmware powering the Lumysi wearable. You will develop, optimize, and maintain low-level software in C/C++ for battery-powered devices, integrating sensors, BLE, and RTOS.

You will collaborate with hardware, mobile, and manufacturing teams to ensure robust, power-efficient performance from prototype to production, shaping the device’s reliability and battery life.

Qualifications

• 4+ years of embedded firmware development experience.
• Strong programming in C and C++ for bare-metal/RTOS environments.
• Experience with Nordic and Espressif platforms and BLE.
• Sensor driver development and integration experience.
• Ability to read schematics/datasheets and debug with test equipment.

Responsibilities

• Develop and maintain embedded firmware in C and C++.
• Implement I2C, SPI, UART and BLE communications.
• Create low-power strategies and power-state management.
• Develop or integrate sensor drivers and BLE services.
• Collaborate with hardware, mobile and QA teams; support production.

Skills

C/C++

BLE

Nordic nRF52/53

Espressif

Sensor drivers

RTOS

Power optimization

I2C/SPI/UART

Git

English proficiency

Education

Electronics/Electrical/CS or related

Tools

Oscilloscope

Logic Analyzer

Debugger

Job description

Lumysi is a US-based wearable technology startup developing a jewelry-inspired health and fitness bracelet.

Our screenless wearable continuously tracks health, activity, sleep, recovery, and women’s health metrics while maintaining the appearance and comfort of a premium accessory.

The product combines biometric sensors, ultra-low-power embedded systems, Bluetooth connectivity, interchangeable straps, and a mobile application that transforms health data into personalized insights.

We are expanding our engineering team and looking for an experienced Embedded Firmware Engineer to take ownership of the firmware that powers the Lumysi wearable.

The Role

As an Embedded Firmware Engineer, you will develop, optimize, and maintain the embedded software running on a battery-powered wearable device.

This is a firmware-focused position. You will work primarily with C and C++, Bluetooth Low Energy, Nordic Semiconductor and Espressif microcontrollers, biometric sensors, communication protocols, power management, and real-time operating systems.

You will collaborate with our hardware engineers, mobile development team, sensor suppliers, and manufacturing partners to ensure reliable performance from prototype development through production.

The ideal candidate has strong low-level programming experience and understands the challenges of building stable, power-efficient firmware for connected, battery-powered devices.

Responsabilities

• Develop and maintain embedded firmware in C and C++.
• Work with Nordic Semiconductor and Espressif microcontrollers.
• Develop and maintain low-level drivers for sensors and peripherals.
• Integrate biometric, motion, temperature, and other wearable sensors.
• Implement communication protocols including I2C, SPI, UART, and BLE.
• Develop and maintain Bluetooth Low Energy connectivity.
• Optimize firmware for ultra-low-power operation and extended battery life.
• Implement power states, sleep modes, wake-up events, and sensor sampling strategies.
• Work with FreeRTOS, Zephyr, or similar embedded operating systems.
• Debug firmware, connectivity, sensor integration, and system-level issues.
• Support firmware testing, validation, version control, and release management.
• Collaborate with mobile developers on BLE services, characteristics, synchronization, and data transfer.
• Support hardware bring-up and prototype testing alongside the hardware engineering team.
• Document firmware architecture, communication protocols, and technical requirements.
• Support manufacturing firmware, device provisioning, calibration, and production testing when required.

Requirements

• Degree in Electronics Engineering, Electrical Engineering, Computer Engineering, Mechatronics, Computer Science, or a related field.
• At least 4 years of professional embedded firmware development experience.
• Strong programming experience in C and C++.
• Experience with low-level, bare-metal, or real-time embedded development.
• Experience with Nordic Semiconductor and/or Espressif platforms.
• Strong understanding of Bluetooth Low Energy.
• Experience implementing I2C, SPI, UART, and other embedded communication protocols.
• Experience developing or integrating sensor drivers.
• Experience with battery-powered or ultra-low-power devices.
• Ability to read electronic schematics and component datasheets.
• Experience debugging embedded systems using oscilloscopes, logic analyzers, debuggers, and other laboratory tools.
• Experience with Git or another version-control system.
• Professional working proficiency in English.
• Ability to work independently in a fast-moving startup environment.

Nice to Have

• Experience with Nordic nRF52 or nRF53 platforms.
• Experience with ESP32 platforms.
• Experience with FreeRTOS or Zephyr.
• Experience with wearable technology, IoT, consumer electronics, or medical technology.
• Experience with PPG, IMU, skin-temperature, or other biometric sensors.
• Experience with over-the-air firmware updates.
• Experience with device provisioning, secure boot, encryption, or embedded security.
• Experience supporting a connected device from prototype through production.
• Familiarity with signal quality, sensor calibration, or biometric-data acquisition.

What We Offer

• The opportunity to build an international wearable technology product.
• Direct collaboration with the founders, engineering team, and manufacturing partners.
• Significant ownership over the firmware of the Lumysi wearable.