Design and Prototyping for GPS Rowing Device
Budget: $1,500 – $3,000 USD
Electronics Engineer — PCB Design, nRF52840 Firmware & Prototype Build (Rowing GPS Device)
PROJECT OVERVIEW
We are building CrewZ — a waterproof GPS rowing performance computer that uses the athlete's own smartphone as the display. The device connects via Bluetooth Low Energy (BLE) and streams real-time rowing metrics (speed, split, stroke rate, power, heart rate zone, check factor) to a companion React Native app.
We need a single experienced freelancer (or small team) to take the project from our detailed technical brief through to a working pilot batch of 5–10 units across two hardware variants.
SCOPE OF WORK
1. PCB Design
4-layer board, 85×45×1.6mm. Key components are fully specified: Nordic nRF52840 microcontroller, u-blox SAM-M10Q GPS (25Hz multi-GNSS), ST LSM6DSO IMU (200Hz), IP68 RGB illuminated pushbutton, TPS63020 3.3V buck-boost rail, MT3608 5V phone charge passthrough, TP5100 Li-ion battery charger, 10Ah Li-ion pouch cell. A second variant (Cox) adds a TI TAS2560 audio amplifier and TPS61170 boost converter. STEP files for the IP68 case and a full component brief are provided after NDA is signed.
2. Firmware
Nordic nRF Connect SDK (Zephyr RTOS), latest stable. The nRF52840 operates as a BLE 5.0 peripheral only. Three custom GATT services are required: Rowing Metrics (broadcast at 5Hz), Device Status (0.2Hz), and Configuration (on change). On-device calculations include: stroke rate (SPM), stroke length, Check Factor (CF%), 500m split, watts (v³ × k-factor), calories (Keytel formula), and HR training zones (Karvonen method). Additional requirements: power button finite state machine, smart Li-ion charging control via GPIO, deep sleep with wake-on-motion (LSM6DSO interrupt), RGB LED state machine, and OTA firmware update support. A mandatory Week 1 deliverable is required before any other work proceeds (see below).
3. Prototyping — 5–10 Units
Source all components, arrange PCB manufacture and assembly, and build a working pilot batch of 5–10 units (mix of Speed and Cox variants). Full board conformal coating required (50µm minimum), with exclusions on USB-C pins, JST-PH connector, and SWD pads. Units must be IP68 sealed within the supplied case form factor. Deliver with firmware flashed and BLE advertising confirmed operational.
PROJECT OVERVIEW
We are building CrewZ — a waterproof GPS rowing performance computer that uses the athlete's own smartphone as the display. The device connects via Bluetooth Low Energy (BLE) and streams real-time rowing metrics (speed, split, stroke rate, power, heart rate zone, check factor) to a companion React Native app.
We need a single experienced freelancer (or small team) to take the project from our detailed technical brief through to a working pilot batch of 5–10 units across two hardware variants.
SCOPE OF WORK
1. PCB Design
4-layer board, 85×45×1.6mm. Key components are fully specified: Nordic nRF52840 microcontroller, u-blox SAM-M10Q GPS (25Hz multi-GNSS), ST LSM6DSO IMU (200Hz), IP68 RGB illuminated pushbutton, TPS63020 3.3V buck-boost rail, MT3608 5V phone charge passthrough, TP5100 Li-ion battery charger, 10Ah Li-ion pouch cell. A second variant (Cox) adds a TI TAS2560 audio amplifier and TPS61170 boost converter. STEP files for the IP68 case and a full component brief are provided after NDA is signed.
2. Firmware
Nordic nRF Connect SDK (Zephyr RTOS), latest stable. The nRF52840 operates as a BLE 5.0 peripheral only. Three custom GATT services are required: Rowing Metrics (broadcast at 5Hz), Device Status (0.2Hz), and Configuration (on change). On-device calculations include: stroke rate (SPM), stroke length, Check Factor (CF%), 500m split, watts (v³ × k-factor), calories (Keytel formula), and HR training zones (Karvonen method). Additional requirements: power button finite state machine, smart Li-ion charging control via GPIO, deep sleep with wake-on-motion (LSM6DSO interrupt), RGB LED state machine, and OTA firmware update support. A mandatory Week 1 deliverable is required before any other work proceeds (see below).
3. Prototyping — 5–10 Units
Source all components, arrange PCB manufacture and assembly, and build a working pilot batch of 5–10 units (mix of Speed and Cox variants). Full board conformal coating required (50µm minimum), with exclusions on USB-C pins, JST-PH connector, and SWD pads. Units must be IP68 sealed within the supplied case form factor. Deliver with firmware flashed and BLE advertising confirmed operational.
Related categories:
Electronics
Microcontroller
PCB Layout
Product Design
GPS
Bluetooth Low Energy (BLE)
Embedded Systems
Prototyping