Sr. Firmware Engineer/Consultant 100% Remote
About the role:
We need a hands-on firmware consultant who owns the cellular stack end to end: modem integration, RF bring-up, firmware, carrier and regulatory certification.
You will work onsite in Oak Brook alongside hardware, firmware, cloud and compliance teams to take products from prototype through certification and production.
Key responsibilities:
Cellular firmware:
Design, develop and debug embedded C/C++ firmware integrating LTE-M, NB-IoT and/or LTE Cat-1/Cat-1bis modules into commercial door and lift controllers
Integrate modems (e.g., Nordic nRF91, Quectel, u-blox, Telit, Sierra Wireless) via AT commands or vendor SDKs
Implement network attach, PDP context, PSM/eDRX power saving, reconnect and fallback logic
Build secure connectivity to the cloud: TLS/DTLS, MQTT/CoAP, device provisioning, and certificate management
Implement and validate firmware-over-the-air (FOTA) updates for both the host MCU and the modem
Support SIM, eSIM/eUICC and carrier profile management
Radio and hardware:
Partner with hardware engineers on antenna selection, placement and tuning inside metal commercial enclosures
Run RF bring-up and performance testing (TRP/TIS, signal quality, coverage) using call boxes and network emulators
Debug with spectrum analyzers, logic analyzers, modem trace tools and JTAG/SWD
Regulatory and carrier certification:
Lead the product through FCC (Part 15, 22, 24, 27), ISED, PTCRBF and carrier certification (AT&T, Verizon, T-Mobile)
Coordinate with test labs, module vendors and carriers; prepare test plans and certification documentation
Address RF exposure, EMC and module-certification reuse requirements
Collaboration:
Work with product management, cloud, QA and compliance to define requirements and test strategy
Document architecture, design decisions and test results; mentor internal engineers on cellular best practices
Required qualifications:
8+ years of embedded firmware development in C/C++ on 32-bit MCUs (ARM Cortex-M or similar)
4+ years hands-on with cellular IoT (LTE-M, NB-IoT, LTE Cat-1, or Cat-4) shipped in production products
Deep knowledge of 3GPP LTE concepts: attach/registration, bands, PSM/eDRX, RRC states, roaming
Direct experience taking a cellular product through PTCRBF and at least one US carrier certification
Working knowledge of FCC/ISED regulatory requirements for intentional radiators
RTOS experience (FreeRTOS, Zephyr, ThreadX or similar)
Comfortable with lab RF tools: call box/network emulator, spectrum analyzer, oscilloscope
Able to work onsite in Oak Brook, IL
Bachelor's degree in Electrical Engineering, Computer Engineering or equivalent experience
Preferred qualifications:
Experience in garage door, access control, building automation, industrial IoT or other commercial connected products
Hands-on with Nordic nRF91 series and the nRF Connect SDK / Zephyr
Knowledge of LTE Cat-1bis, 5G RedCap or 2G/3G sunset migration
Background in antenna design or RF hardware, not just firmware
Experience with AWS IoT, Azure IoT Hub or similar device clouds
Familiarity with product security standards (UL 2900, ETSI EN 303 645, IEC 62443)
Experience with UL safety requirements for motorized door operators (e.g., UL 325)
