The schematic build made partial progress: 19 primary/interface components were added, including the nRF52840 module, MAX-F10S GNSS, BMP581 barometer, 32 MB flash, charger, regulator, USB protection, button, RGB LED, SWD/battery connectors, U.FL test path, and magnetic USB contacts.
Still incomplete
Components are not wired; the project still has zero nets.
Support passives and ceramic antenna integration are missing.
Datasheet checks, power-budget update, ERC review, and fixes remain.
The top-mounted-button enclosure revision was still in progress and was not verified.
This has not reached the schematic-completion checkpoint, so PCB placement, routing, and manufacturing files have not started. Execution stopped because your ACUs ran out.
The enclosure revision completed successfully: the button is now on the sky-facing top surface, outside the ceramic GNSS antenna keep-out. The mechanical brief and enclosure concept were updated accordingly.
The project remains before the schematic checkpoint: the 19 primary components are present but unwired, with support passives, antenna integration, power verification, and ERC still outstanding. PCB placement/routing cannot begin safely yet.
Define the electrical, RF, mechanical, manufacturing, and validation constraints for the first EVT PCB of the ski logger. Exact architecture-defining parts remain at a user selection checkpoint; support parts may be finalized during schematic capture.
Fixed Product Requirements
Removable upper-back vest logger for cross-country skiing.
Dual-band GNSS position logging at 10 Hz for up to 10 hours.
BLE Central connection to a standard heart-rate strap throughout recording.
BLE phone synchronization and USB transfer after recording.
Barometric altitude, 32 MB or greater onboard flash, one button, and one RGB LED.
Operation target: 10 hours at -10 °C with battery aging and reserve margin.
PCB Envelope
Maximum outline: 55 x 30 mm, rectangular with rounded board corners where enclosure retention permits.
Thickness: 1.0 mm, four-layer FR-4.
No components beneath the GNSS ceramic patch except its documented feed/ground structure.
Battery is off-board and occupies the enclosure region below or beside the non-GNSS electronics zone.
Mounting-hole positions remain PROVISIONAL until the enclosure concept is accepted.
BLE module antenna at the opposite board edge, clear of battery, ground, metal, and magnetic connector.
Charger, buck converter, USB protection, and magnetic connector at the service end.
Barometer adjacent to the enclosure membrane vent and isolated from charger heat and direct airflow jets.
Stackup
Table
Layer
Function
L1
RF, USB, critical signals, components
L2
Unbroken ground reference
L3
Power distribution and low-speed signals
L4
Secondary signals and selected passives
Fabricator stackup must be chosen before calculating RF and USB trace geometry.
GNSS feed: 50-ohm grounded coplanar waveguide with via fence and a pi matching footprint.
USB D+/D-: 90-ohm differential target, short, length-balanced, and protected next to the external contacts.
Selected Baseline Components
Selection status: Accuracy-first balanced baseline approved. The design prioritizes the best practical standalone GNSS accuracy within a €30 electronics BOM target at 1k+ quantity.
Table
Function
Exact part
Rationale
BLE MCU module
Raytac MDBT50Q-1MV2
nRF52840 module, integrated BLE antenna, lower RF integration risk, available Flux footprint
GNSS receiver
u-blox MAX-F10S-00B
Compact L1/L5 receiver, 10 Hz capability, low tracking power, integrated LNA/SAW, active Flux part
GNSS antenna
Aboosty AIGC041 / Z01-0800240R0A
Passive stacked L1/L5 patch optimized around a compact 26 x 26 mm ground plane; best fit for the 30 mm board width
Barometer
Bosch BMP581
Low current, high-resolution pressure sensing, active Flux part
Flash
Winbond W25Q256JVEIQ or compatible 32 MB WSON-8 variant
32 MB capacity with compact package; exact suffix selected for voltage and sourcing
Charger/power path
TI BQ24074RGTR
Single-cell linear charging, power-path operation, NTC support, active Flux part
3.3 V buck
TI TPS62840DLCR
Very low quiescent current and ample transient margin, active Flux part
USB ESD
ST USBLC6-2SC6
USB 2.0 differential ESD protection, active Flux part
Magnetic interface
Custom ENIG hard-gold PCB contact pads with keyed 4-pin magnetic pogo cable
Preserves USB 2.0 and charging while avoiding the cost and volume of an industrial connector system
Battery
THOR-503450, 1000 mAh, protected, with NTC
5 x 34 x 50 mm class, -20 °C discharge rating; supplier documentation and samples required before freeze
Architecture Alternatives and Trade-offs
BLE Module
Table
Option
Advantages
Disadvantages
Raytac MDBT50Q-1MV2
Lowest cost of the module candidates; compact; integrated antenna; available Flux footprint
Less shielding/integration support than u-blox; antenna keepout still dominates layout
Larger and more expensive; reduces layout flexibility
Bare nRF52840
Lowest unit cost and smallest optimized production solution
Highest RF, crystal, certification, and layout risk; inappropriate for the first EVT unless size becomes dominant
GNSS Receiver
Table
Option
Advantages
Disadvantages
u-blox MAX-F10S-00B
Compact, low-power L1/L5, 10 Hz, strong tools/documentation, available Flux footprint
Higher unit cost than Quectel; no GLONASS support in the listed F10 configuration
Quectel LC29H-AA
Lower module cost, L1/L5, broad constellation support
Larger, higher current, weaker Flux-library support, and more integration evidence must be sourced
ST Teseo-LIV4F
Broad constellation support, 10 Hz dual-band, mature ST ecosystem
Highest tracking current of the main candidates; no ready Flux part found for LIV4F
GNSS Antenna
Table
Option
Advantages
Disadvantages
Aboosty AIGC041, passive stacked
Recommended: compact 25 mm footprint and unusually small reference ground plane; no antenna current
Approximately 8 mm stack height; requires RF matching and prototype tuning; vendor supply chain is less established than Taoglas/TE
Joymax PPX-C025L25B 3, passive stacked
Established DigiKey path; L1/L2/L5; high-temperature rating
8 mm height and approximately 60 x 60 mm reference ground plane, much larger than the PCB
Synzen RHEA SZA-N-3G26, active
Integrated LNA/filtering, good weak-signal potential, cable allows flexible placement
About 20 mA additional load, 20 g mass, more internal cable volume, and higher BOM cost
TE ANT-GNCP-C25L125100, active
Ground-plane independent and strong vendor support
12 mm height, 10–15 mA load, making the enclosure substantially thicker
Selected Antenna
Use Aboosty AIGC041 / Z01-0800240R0A for EVT because it is the reviewed dual-band ceramic patch whose 26 x 26 mm reference ground plane best matches the available 30 mm PCB width. This maximizes the chance of retaining useful L1/L5 performance without enlarging the pod. Treat matching and sensitivity as an EVT validation item. Keep a U.FL test connector or switchable RF path on the first PCB so a calibrated external active antenna can be compared without redesigning the receiver section.
Cost Allocation Target
The following is a design allocation rather than a supplier quote. It must be confirmed after distributor and assembly quotations.
Table
Group
1k+ target allocation
Raytac BLE module
€4.00–5.50
u-blox MAX-F10S
€7.00–9.00
AIGC041 antenna and RF matching
€3.00–5.00
Battery with protection and NTC
€3.00–4.50
Barometer and 32 MB flash
€2.00–3.00
Charger, regulator, USB protection, UI, passives
€3.50–5.00
PCB contact interface and battery interconnect
€0.50–1.00
Estimated electronics BOM
€23.00–33.00
To hold the requested ceiling, sourcing targets are MAX-F10S at or below €8, antenna at or below €4, and the complete battery at or below €4. The PCB will support drop-in value engineering for the flash, RGB LED, and passives, but not at the expense of GNSS, RF matching, battery protection, or USB ESD.
Power Architecture
Diagram
Charge current baseline: 300 mA, subject to battery supplier approval and thermal testing.