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Hardware Requirements Specification

Document ID: HW-REQ-001
Version: 1.0
Last Updated: November 2024
Status: Active
Owner: Hardware Engineering Lead

Document Purpose​

This Hardware Requirements document defines the complete physical, electrical, and mechanical specifications for all Groot Force variants. It serves as the authoritative reference for component selection, PCB design, manufacturing, and quality assurance.

1. Frame Architecture​

1.1 Structural Requirements​

REQ-HW-001 [P0]
The frame shall use magnesium alloy spine for thermal and structural integrity with TR90/carbon fiber outer shell.

Rationale: Magnesium provides heat dissipation and strength at low weight.
Specification: AZ91D or similar magnesium alloy, 1.5-2.0mm wall thickness
Validation: Thermal conductivity > 150 W/m·K, tensile strength > 250 MPa
Traces to: REQ-PRD-009, REQ-THERMAL-001

REQ-HW-002 [P0]
Base variants shall weigh 55-58g, consumer variants 48-55g, ruggedized variants up to 62g.

Rationale: Weight distribution for all-day comfort varies by use case.
Specification:

  • EYON: 48-50g
  • GF-LX, GF-TR, GF-NF: 52-55g
  • GF-BE, GF-CL, GF-VI, GF-DI: 55-58g
  • GF-TX: 58-62g

Validation: Mass measurements with ±0.5g accuracy, user comfort testing > 8 hours
Traces to: REQ-PRD-007

REQ-HW-003 [P0]
The frame shall withstand drop test from 1.2m height onto concrete without structural failure.

Rationale: Realistic drop protection for everyday use.
Specification: 6 drops per axis (18 total), no cracks or functional failures
Validation: Drop testing per IEC 60068-2-31

REQ-HW-004 [P0]
Hinge flex cable shall survive minimum 30,000 bend cycles.

Rationale: Typical device lifetime with multiple daily open/close cycles.
Specification: 0.15mm FPCB with copper shield, over-molded TPU
Validation: Cyclic bend testing with continuity monitoring

1.2 Thermal Architecture​

REQ-HW-010 [P0]
The magnesium spine shall function as primary thermal path from SoC to frame perimeter.

Rationale: Passive cooling essential for fanless operation.
Specification:

  • Thermal interface: Graphite pad 300 W/m·K
  • Contact area: > 400mm²
  • Heat pipe optional for premium variants

Validation: Thermal imaging under 3W sustained load, surface temp < 38°C
Traces to: REQ-SRS-130, REQ-THERMAL-001

REQ-HW-011 [P0]
Surface temperature at user contact points shall not exceed 40°C during normal operation.

Rationale: User comfort and safety, prevents burns.
Specification: Measured at nose bridge, temple contacts, ear hooks
Validation: Thermal testing per IEC 60950-1
Traces to: REQ-PRD-230

1.3 Environmental Protection​

REQ-HW-020 [P1]
Standard variants shall achieve IP54 rating (dust and splash protected).

Rationale: Protection against sweat, rain, and everyday exposure.
Specification:

  • Dust ingress: Limited (category 5)
  • Water ingress: Splash resistant (category 4)

Validation: Testing per IEC 60529
Traces to: REQ-PRD-010

REQ-HW-021 [P1]
Ruggedized variants (GF-TX) shall achieve IP65 rating.

Rationale: Trade and industrial environments require higher protection.
Specification:

  • Dust ingress: No ingress (category 6)
  • Water ingress: Low-pressure jet (category 5)

Validation: Testing per IEC 60529

REQ-HW-022 [P1]
EYON variant shall achieve IP67 rating (submersion protected).

Rationale: Outdoor adventure and water sports use cases.
Specification:

  • Dust ingress: No ingress (category 6)
  • Water ingress: 1m depth for 30 minutes (category 7)

Validation: Submersion testing per IEC 60529

2. Electronics Architecture​

2.1 Main Processing Unit​

REQ-HW-030 [P0]
The main SoC shall be either Rockchip RK3588 or Qualcomm Snapdragon XR2 Gen 2.

Rationale: Balance of performance, power efficiency, and AR capability.
Specification:

  • RK3588: 8-core (4×A76 + 4×A55), Mali-G610 MP4, 6 TOPS NPU
  • XR2 Gen 2: 8-core Kryo, Adreno 740, Hexagon DSP

Validation: Benchmark testing for AI inference, graphics, thermal profile

REQ-HW-031 [P0]
RAM shall be 4-6GB LPDDR5 with minimum 4266MHz speed.

Rationale: Sufficient for LLM inference and multitasking.
Specification:

  • Base variants: 4GB
  • Premium variants: 6GB

Validation: Memory bandwidth and latency testing

REQ-HW-032 [P0]
Storage shall be 128GB UFS 3.1 internal with microSD expansion support.

Rationale: Fast storage for AI models, user data, and media.
Specification:

  • Sequential read: > 1000 MB/s
  • Sequential write: > 500 MB/s

Validation: Storage performance benchmarking

2.2 Display System​

REQ-HW-040 [P0]
The display shall use dual micro-OLED waveguides at 1080p per eye, 85° FOV, 1200 nits brightness.

Rationale: High resolution and brightness required for outdoor visibility.
Specification:

  • Resolution: 1920×1080 per eye
  • Refresh: 60Hz minimum (90Hz preferred)
  • Contrast: > 100,000:1
  • Color gamut: > 90% DCI-P3

Validation: Display characterization testing
Traces to: REQ-PRD-010, REQ-SRS-005

REQ-HW-041 [P0]
Waveguide optical system shall provide edge-to-edge clarity with < 5% distortion.

Rationale: AR overlays must align precisely with real world.
Specification:

  • Exit pupil: 8mm minimum
  • Eye relief: 12-15mm
  • Chromatic aberration: < 2 pixels

Validation: Optical testing with collimator

REQ-HW-042 [P0]
Ambient light sensor shall measure 0.1 lux to 100,000 lux range with auto-brightness.

Rationale: Adaptive brightness for indoor to bright outdoor conditions.
Specification: APDS-9960 or equivalent, 16-bit ADC
Validation: Brightness curve calibration across light range

2.3 Camera System​

REQ-HW-050 [P1]
Standard variants shall include dual 12MP cameras with autofocus.

Rationale: Essential for computer vision, OCR, and documentation.
Specification:

  • Sensor: IMX577 or equivalent
  • Lens: f/1.8, 6-element
  • Focus: PDAF, 10cm to infinity

Validation: Image quality testing per ISO 12233

REQ-HW-051 [P1]
Premium variants (GF-TX) shall include dual 32MP cameras with stabilization.

Rationale: Professional documentation and AR measurement require higher resolution.
Specification:

  • Sensor: IMX686 or equivalent
  • Lens: f/1.8, 7-element
  • Stabilization: OIS or EIS

Validation: Resolution, noise, stabilization effectiveness testing

REQ-HW-052 [P0]
Camera hardware LED indicator shall illuminate whenever camera is active.

Rationale: Privacy - visible recording indicator.
Specification: Red LED, > 1 cd intensity, non-defeatable
Validation: LED timing synchronized with camera power
Traces to: REQ-SRS-063

2.4 Audio System​

REQ-HW-060 [P0]
Audio output shall use bone conduction transducers for open-ear listening.

Rationale: Maintains environmental awareness while delivering audio.
Specification:

  • Frequency response: 200Hz-8kHz
  • Output: 90dB SPL @ 10cm
  • THD: < 3%

Validation: Audio quality testing per IEC 60268
Traces to: REQ-PRD-040

REQ-HW-061 [P0]
Microphone array shall include 4× digital MEMS microphones with beamforming.

Rationale: Directional audio capture and noise cancellation.
Specification:

  • SNR: > 64dB
  • Sensitivity: -38dBV
  • Array geometry: 2 per temple

Validation: Beamforming effectiveness and noise rejection testing
Traces to: REQ-PRD-042

2.5 Sensor Suite​

REQ-HW-070 [P0]
All variants shall include 9-axis IMU (accelerometer, gyroscope, magnetometer).

Rationale: Core sensor for orientation, gestures, and fall detection.
Specification:

  • IMU: ICM-20948 or equivalent
  • Accel range: ±16g
  • Gyro range: ±2000°/s
  • Mag resolution: 0.15 µT

Validation: IMU calibration and accuracy testing
Traces to: REQ-SENSOR-001, REQ-PRD-050

REQ-HW-071 [P1]
NDIS and enterprise variants shall include ToF depth sensor (VL53L5CX, 8×8 zones, 4m range).

Rationale: Essential for obstacle detection and gesture recognition.
Specification:

  • Range: 0.2-4m
  • Accuracy: ±25mm @ 1m
  • Frame rate: 30Hz

Validation: Depth accuracy and range testing
Traces to: REQ-SENSOR-002, REQ-PRD-051

REQ-HW-072 [P2]
Premium variants shall include LiDAR (TFmini-S, 12m range).

Rationale: Walking assistance and navigation require longer range detection.
Specification:

  • Range: 0.3-12m
  • Accuracy: ±1% @ 6m
  • FOV: 2°

Validation: LiDAR accuracy testing in varied conditions
Traces to: REQ-SENSOR-003, REQ-PRD-052

REQ-HW-073 [P0]
All variants shall include environmental sensor (BME688).

Rationale: Air quality, temperature, humidity monitoring for health and safety.
Specification:

  • Temperature: -40 to 85°C, ±1°C
  • Humidity: 0-100% RH, ±3%
  • Pressure: 300-1100 hPa, ±1 hPa
  • Gas (VOC): 1-500 IAQ index

Validation: Sensor calibration and accuracy testing

REQ-HW-074 [P1]
Fitness and wellness variants shall include health sensors (MAX30102 or equivalent).

Rationale: Heart rate and SpO2 tracking for fitness applications.
Specification:

  • Heart rate: 30-200 bpm, ±2 bpm
  • SpO2: 70-100%, ±2%
  • Green LED: 537nm, Red LED: 660nm

Validation: Accuracy testing vs medical-grade reference
Traces to: REQ-PRD-053, REQ-PRD-140

REQ-HW-075 [P1]
Health variants shall include temperature sensor (MLX90614 or equivalent).

Rationale: Contactless forehead temperature for health monitoring.
Specification:

  • Range: 0-50°C (body temp mode)
  • Accuracy: ±0.2°C
  • Response time: < 1s

Validation: Temperature accuracy testing

3. Power System​

3.1 Battery Architecture​

REQ-HW-080 [P0]
The power system shall use dual 900mAh LiPo cells (one per temple) with symmetric configuration.

Rationale: Balanced weight distribution and power redundancy.
Specification:

  • Chemistry: LiPo (Lithium Polymer)
  • Voltage: 3.7V nominal, 4.2V max
  • Capacity: 900mAh per cell (1800mAh total)
  • Dimensions: Custom pouch cell

Validation: Capacity testing per IEC 61960
Traces to: REQ-PRD-008, REQ-HW-020

REQ-HW-081 [P0]
Each battery cell shall include PCM (Protection Circuit Module) with over-charge, over-discharge, over-current protection.

Rationale: Essential safety protection for lithium batteries.
Specification:

  • Over-charge cutoff: 4.25V ±0.05V
  • Over-discharge cutoff: 2.8V ±0.1V
  • Over-current: 2.5A cutoff

Validation: Protection circuit testing
Traces to: REQ-SAFETY-001, REQ-PRD-231

REQ-HW-082 [P0]
Each battery shall include NTC thermistor for temperature monitoring.

Rationale: Prevents charging or operation at unsafe temperatures.
Specification:

  • Thermistor: 10kΩ @ 25°C, B-constant 3380K
  • Operating temp: 0-45°C
  • Charging temp: 0-45°C

Validation: Temperature monitoring and cutoff testing

REQ-HW-083 [P0]
Each battery circuit shall include polyfuse (1.5A) for short-circuit protection.

Rationale: Resettable fuse prevents catastrophic failure from shorts.
Specification:

  • Hold current: 1.0A
  • Trip current: 2.0A
  • Max voltage: 6V

Validation: Fuse trip testing and reset verification

REQ-HW-084 [P0]
Battery cells shall meet UN38.3 transportation safety requirements.

Rationale: Required for international shipping compliance.
Specification: Pass all 8 UN38.3 tests
Validation: Third-party testing and certification

3.2 Power Management​

REQ-HW-090 [P0]
The PMIC shall provide regulated power rails: 5V, 3.3V, 1.8V, 1.2V with < 50mV ripple.

Rationale: Clean power required for sensitive analog circuits.
Specification:

  • 5V rail: USB input, battery charging
  • 3.3V rail: Sensors, displays
  • 1.8V rail: Logic, I/O
  • 1.2V rail: SoC core

Validation: Power rail quality measurement under load

REQ-HW-091 [P0]
PMIC components shall include: BQ25895 (charging), TPS62840 (buck), TPS61236P (boost).

Rationale: Proven, efficient ICs for battery-powered devices.
Specification:

  • Charging: 5V/1A input, 0.5-2A charge current
  • Buck: 92% efficiency @ 1A
  • Boost: 95% efficiency @ 500mA

Validation: Efficiency and thermal testing

REQ-HW-092 [P0]
Battery runtime shall meet minimum 6 hours active use.

Rationale: Full work day coverage essential for all use cases.
Specification: Active use defined as:

  • Display on 50% brightness
  • AI queries every 5 minutes
  • Sensors active
  • Moderate audio use

Validation: Runtime testing under standardized usage profile
Traces to: REQ-PRD-008, REQ-PRD-210

REQ-HW-093 [P1]
Extended runtime of 12+ hours shall be achievable via power optimization or optional battery tether.

Rationale: Extended work shifts and outdoor adventures.
Specification:

  • Power modes reduce consumption 30-50%
  • Battery tether adds 2000mAh capacity

Validation: Extended runtime testing

3.3 Charging System​

REQ-HW-100 [P0]
Charging shall support USB-C Power Delivery (5V/2A minimum, 9V/1.5A preferred).

Rationale: Fast charging with common USB-C chargers.
Specification:

  • Charge time: 0-80% in 45 minutes @ 9V/1.5A
  • Charge time: 0-100% in 90 minutes @ 9V/1.5A

Validation: Charge rate and thermal testing

REQ-HW-101 [P1]
EYON variant shall support Qi2 magnetic wireless charging.

Rationale: Convenient wireless charging for lifestyle variant.
Specification:

  • Qi2 15W magnetic alignment
  • Charge time: 0-80% in 60 minutes

Validation: Wireless charging efficiency and alignment testing

REQ-HW-102 [P1]
EYON variant shall include solar charging capability.

Rationale: Extended battery life for outdoor use, unique differentiator.
Specification:

  • Solar cells: Transparent thin-film on temple sides
  • Output: 50-100mW in direct sunlight
  • Battery extension: +20-30% daily in typical outdoor use

Validation: Solar efficiency testing under various light conditions
Traces to: REQ-PRD-151

4. Connectivity​

4.1 Wireless Connectivity​

REQ-HW-110 [P0]
The system shall include Wi-Fi 6 (802.11ax) radio with 2.4GHz and 5GHz bands.

Rationale: Modern Wi-Fi standard for performance and efficiency.
Specification:

  • TX power: 15dBm typical
  • RX sensitivity: -75dBm @ MCS0
  • Antenna: PCB trace or ceramic

Validation: Wi-Fi performance and range testing
Traces to: REQ-SRS-140

REQ-HW-111 [P0]
The system shall include Bluetooth 5.3 with LE Audio support.

Rationale: Low-power connectivity for companion app and accessories.
Specification:

  • TX power: 0dBm
  • RX sensitivity: -95dBm
  • LE Audio codec support

Validation: Bluetooth pairing, range, audio quality testing

REQ-HW-112 [P1]
Enterprise variants shall support optional LTE Cat-4 connectivity via eSIM.

Rationale: Enables field use without Wi-Fi dependency.
Specification:

  • Bands: Global LTE support
  • Throughput: 150Mbps down, 50Mbps up
  • eSIM: MFF2 form factor

Validation: Cellular connectivity and band testing
Traces to: REQ-SRS-141

4.2 Wired Connectivity​

REQ-HW-120 [P0]
USB-C port shall support USB 2.0 data (480Mbps) and USB PD charging.

Rationale: Sufficient for firmware updates, data transfer, and charging.
Specification:

  • Connector: USB Type-C receptacle
  • Data: USB 2.0 High-Speed
  • Power: USB PD 3.0, 5-9V negotiation

Validation: USB enumeration, transfer speed, PD negotiation testing

REQ-HW-121 [P1]
Optional battery tether shall use magnetic pogo-pin connector (4-pin).

Rationale: Reliable, waterproof connection for extended battery.
Specification:

  • Pins: VBAT, GND, I2C_SDA, I2C_SCL
  • Current rating: 2A continuous
  • Magnetic alignment: 4N force

Validation: Connection reliability and electrical testing

5. PCB Architecture​

5.1 Board Layout​

REQ-HW-130 [P0]
The electronics shall use 3-board modular architecture: main logic, sensor, power/audio.

Rationale: Modularity enables variant customization without full redesign.
Specification:

  • Main board: SoC, RAM, storage, connectivity
  • Sensor board: IMU, ToF, LiDAR, environmental
  • Power/audio board: PMIC, battery protection, audio amp

Validation: Electrical testing of each board independently

REQ-HW-131 [P0]
PCBs shall be 6-layer with controlled impedance for high-speed signals.

Rationale: Signal integrity for MIPI, USB, Wi-Fi traces.
Specification:

  • Layer stack: Sig-GND-Sig-Pwr-Sig-Sig
  • Impedance: 50Ω single-ended, 90Ω differential
  • Board thickness: 0.8mm

Validation: Impedance measurement with TDR

REQ-HW-132 [P0]
FPC (Flexible Printed Circuit) shall connect boards with shielded construction.

Rationale: Flexibility for hinge movement, EMI protection.
Specification:

  • Substrate: Polyimide, 0.15mm thickness
  • Shield: Copper foil coverage
  • Bend radius: > 5mm minimum

Validation: Flex cycle testing, signal integrity measurement

5.2 EMC & EMI​

REQ-HW-140 [P0]
The device shall meet FCC Part 15 Class B and CE EMC directive emissions limits.

Rationale: Regulatory requirement for consumer electronics.
Specification:

  • Radiated emissions: < 40 dBμV/m @ 3m (30-1000 MHz)
  • Conducted emissions: < 60 dBμV (150kHz-30MHz)

Validation: EMC testing in certified lab
Traces to: REQ-COMPLIANCE-010

REQ-HW-141 [P0]
High-speed signal traces shall include appropriate termination and ground return paths.

Rationale: Minimizes emissions and crosstalk.
Specification:

  • Differential pairs: matched length ±5 mils
  • Ground vias: < 1mm from signal transitions
  • Termination: Series resistors per signal type

Validation: Signal integrity testing with oscilloscope

6. Mechanical Specifications​

6.1 Dimensions​

REQ-HW-150 [P0]
Frame dimensions shall accommodate 95th percentile head sizes.

Rationale: Inclusive design for broad user base.
Specification:

  • Temple length: 135-145mm adjustable
  • Bridge width: 18-20mm
  • Lens width: 50-55mm per eye

Validation: Fit testing across diverse user group

REQ-HW-151 [P1]
Device shall include adjustable nose pads for comfort and alignment.

Rationale: Ensures proper optical alignment and reduces pressure points.
Specification:

  • Adjustment range: ±3mm vertical
  • Material: Soft silicone
  • Hypoallergenic

Validation: User comfort testing

6.2 Materials​

REQ-HW-160 [P0]
All user-contact materials shall be hypoallergenic and skin-safe.

Rationale: Prevents allergic reactions during extended wear.
Specification:

  • Frame: Medical-grade TR90 or titanium
  • Nose pads: Silicone, ISO 10993 certified
  • Coatings: Nickel-free

Validation: Biocompatibility testing per ISO 10993

REQ-HW-161 [P1]
Materials shall meet RoHS and REACH compliance for hazardous substances.

Rationale: Environmental and health regulations.
Specification:

  • Lead-free solder
  • Halogen-free PCB substrate
  • Phthalate-free plastics

Validation: Material composition testing

7. Manufacturing Tolerances​

7.1 Dimensional Tolerances​

REQ-HW-170 [P0]
Critical optical components shall maintain tolerances of ±0.08mm or better.

Rationale: Optical alignment critical for AR overlay accuracy.
Specification:

  • Display module alignment: ±0.08mm
  • Waveguide position: ±0.05mm
  • Lens housing: ±0.1mm

Validation: CMM (Coordinate Measuring Machine) inspection

REQ-HW-171 [P0]
Battery channels shall provide 0.18-0.22mm clearance for cell swelling.

Rationale: Lithium batteries expand during aging, requires room.
Specification:

  • Cell dimensions: tolerance ±0.2mm
  • Channel fit: snug but not tight

Validation: Fit testing with aged battery cells

7.2 Assembly Tolerances​

REQ-HW-180 [P0]
PCB placement accuracy shall be ±0.05mm for fine-pitch components.

Rationale: 0.4mm pitch QFN/BGA packages require precision placement.
Specification:

  • Pick-and-place accuracy: ±0.03mm
  • Solder paste stencil: 0.1mm thickness

Validation: AOI (Automated Optical Inspection) and X-ray inspection

8. Quality Assurance​

8.1 Incoming Inspection​

REQ-HW-190 [P0]
All critical components shall undergo incoming quality inspection.

Rationale: Prevents defective parts from entering assembly.
Specification:

  • Visual inspection: 100% for mechanical parts
  • Electrical testing: Sample testing (AQL 1.0) for electronics

Validation: Documented inspection procedures

8.2 In-Process Testing​

REQ-HW-191 [P0]
PCBs shall undergo electrical testing before assembly into frames.

Rationale: Catches defects early, reduces rework costs.
Specification:

  • Continuity testing
  • Short circuit detection
  • Power-on self-test (POST)

Validation: Test coverage > 95% of nets

8.3 Final Testing​

REQ-HW-192 [P0]
All assembled units shall undergo comprehensive final testing.

Rationale: Ensures only functional units ship to customers.
Specification:

  • Boot test
  • Display test
  • Sensor calibration
  • Camera test
  • Audio test
  • Connectivity test
  • IP rating spot check (sample)

Validation: Test plan with pass/fail criteria, < 2% failure rate

9. Reliability & Lifetime​

9.1 MTBF (Mean Time Between Failures)​

REQ-HW-200 [P1]
Device MTBF shall be > 10,000 hours under normal operating conditions.

Rationale: Equivalent to > 1 year of 24/7 operation or ~3 years typical use.
Specification:

  • Operating temp: 0-40°C
  • Normal use: 8 hours/day

Validation: Accelerated life testing, failure rate analysis

9.2 Battery Lifecycle​

REQ-HW-201 [P0]
Battery shall retain > 80% capacity after 500 charge cycles.

Rationale: Standard lithium battery specification, ensures multi-year lifespan.
Specification:

  • Charge cycle: 0-100% discharge/recharge
  • Testing: 500 cycles @ 25°C

Validation: Capacity testing per IEC 61960

10. Environmental Specifications​

10.1 Operating Conditions​

REQ-HW-210 [P0]
Operating temperature range: 0°C to 40°C (extended: -10°C to 45°C).

Rationale: Covers most real-world usage environments.
Specification:

  • Standard operation: 0-40°C
  • Extended (reduced performance): -10 to 45°C

Validation: Temperature chamber testing

REQ-HW-211 [P0]
Operating humidity range: 10% to 85% RH, non-condensing.

Rationale: Protects electronics from moisture damage.
Specification: No condensation on internal components
Validation: Humidity chamber testing

10.2 Storage Conditions​

REQ-HW-220 [P0]
Storage temperature range: -20°C to 60°C.

Rationale: Wider range than operating for shipping and warehousing.
Specification:

  • Battery state: 40-60% charge for long-term storage

Validation: Storage conditioning testing

11. Regulatory Compliance​

REQ-HW-230 [P0]
Hardware shall meet all requirements for: RCM, FCC, CE, UN38.3, IEC 62368-1.

Rationale: Required certifications for global market.
Validation: Third-party certification and testing
Traces to: Compliance Document