Embedded Systems Engineer (Nordic nRF91): firmware and PCB design for a compact cellular IoT

We are a UK software and AI consultancy building a compact, body-worn connected device for a client, and we need one engineer to own the device electronics from schematic to a working pre-production unit. This is a full hardware-and-firmware role, not a firmware-only one: you will design the board, bring it up, write the firmware that runs on it, and hand over a manufacturable design. The device is a small, sealed wearable that uses cellular, pairs to a companion mobile app over Bluetooth LE, and charges wirelessly. The architecture is defined: a Nordic nRF9151 cellular system-in-package as the host, a companion Nordic BLE chip, a 6-axis IMU, a Nordic PMIC with an inductive wireless-charging receiver, a secure element, QSPI flash, dome switches and LED indicators, on a compact 4-layer HDI board inside a sealed enclosure with a fixed mechanical envelope. Battery life is a headline requirement, so low-power design runs through everything. Our team builds the cloud platform and the mobile app; you are the device engineer, working alongside us, an RF/antenna specialist and a mechanical designer. What you will own Hardware design: Finalise the schematic from the defined component set, including power tree, interfaces, SIM, sensors, charging and the RF feed points. Design and lay out the PCB: a compact 4-layer HDI board with WLCSP and LGA parts and an RF section, to the mechanical envelope we provide, coordinating the antenna feeds and matching with the RF specialist. Select and specify the supporting parts (passives, crystal, connectors, battery interface) and produce the bill of materials. Bring the board up: first power-on, rail verification, debug, and rework through prototype revisions. Measure and report the power profile against the battery-life target. Prepare the design for manufacture: fabrication and assembly files, DFM notes and a handover package an EMS can build from. Firmware: Build the device firmware on the nRF9151 with nRF Connect SDK and Zephyr: LTE-M/NB-IoT connectivity, GNSS on demand, MQTT messaging to the cloud, event handling and an over-the-air update path. Implement the companion BLE firmware and the host link between the two chips. Drive power management: PSM and eDRX, microamp sleep, wake on motion, and a measured power budget. Integrate the IMU, secure element, PMIC and charging, switch inputs and indicators. Support integration and testing with the cloud and app teams through to a working unit. Must have A shipped low-power cellular IoT device on the nRF9160 or nRF9151 where you designed the board and wrote the firmware. We will ask to see it. Schematic capture and PCB layout of your own boards in KiCad or Altium, including a 4-layer stackup, fine-pitch WLCSP/LGA parts and an RF section. Hands-on bring-up and debug experience: you have taken a board from first power-on to working, including finding and fixing your own layout mistakes. Demonstrable low-power results with the measurements behind them. nRF Connect SDK / Zephyr, and a companion BLE chip with a host interface to the cellular part. Clear written communication for remote work with a small team. Nice to have Wireless charging integration (inductive receiver ICs and coils). Antenna integration and tuning experience, even where a specialist finalises it. Preparing designs for EMS manufacture and for radio and EMC certification. Sealed or wearable products. Deliverables Schematic, PCB layout and fabrication and assembly files; bill of materials; bring-up notes and power-profile report; firmware source and build system; a documented hardware-and-firmware package ready for manufacturing handover. Engagement Approximately three to four months, starting as soon as possible, remote, with regular overlap with UK working hours. Milestone-based. NDA before detailed briefing; all work assigned to us on completion. Potential for follow-on work as the product develops. To apply Please send: a cellular IoT device you shipped on the nRF91 series or similar where you did both the board and the firmware, and your role in it; an example of a board you laid out yourself; the lowest sleep current you have achieved on a real device and how; your availability; and your hourly rate or a milestone-based fixed price.