Dual-Device Boot Log Analysis - Document Index¶

Date: November 28, 2025 Status: Complete Devices Tested: Dev A (CLIENT), Dev B (SERVER) Test Duration: Two full boot cycles

Overview¶

Comprehensive analysis of two consecutive dual-device boot cycles revealing two critical synchronization failures that prevent the device from meeting EMDRIA therapeutic standards.

Documents in This Analysis¶

1. DUAL_DEVICE_BOOT_ANALYSIS.md (PRIMARY)¶

Comprehensive Technical Analysis (2500+ lines)

Executive summary with severity assessment
Complete root cause analysis for both issues
Detailed boot 1 timeline (full table format)
Detailed boot 2 timeline (offset inversion sequence)
Root cause suspects and code locations
Design improvement recommendations
Test results summary with pass/fail assessment

Use This For: Technical deep-dive, code review, architecture discussions

2. BOOT_ANALYSIS_SUMMARY.txt (EXECUTIVE)¶

High-Level Summary with Actionable Fixes

Quick overview of Issue #1 and Issue #2
Timeline summaries for both issues
Detailed explanations in plain language
Root cause hypotheses
Therapeutic impact assessment
Corrective actions with specific file locations
Testing checklist
Device approval status

Use This For: Management briefing, developer quick-start, initial handoff

3. TIMELINE_TABLES.md (REFERENCE)¶

Detailed Timing Tables and Comparative Analysis

Boot 1 full timeline broken into phases
Boot 2 full timeline with offset values
Comparative analysis (Boot 1 vs Boot 2)
Impact on 20-minute session calculation
BLE notification delivery analysis
RTT offset inversion mathematical analysis
Expected behavior after fixes

Use This For: Debugging, timing validation, regression testing

4. ANALYSIS_QUICK_REFERENCE.txt (POCKET GUIDE)¶

Quick Reference Card

Files created summary
Issue #1 summary (3.7 second delay)
Issue #2 summary (offset inversion)
Therapeutic impact
Debugging checklist
Code review priorities
Expected behavior after fixes

Use This For: Quick lookup, desk reference, testing protocol

Critical Issues Identified¶

Issue #1: SERVER Motor Starts 3.7 Seconds Before CLIENT¶

Severity: CRITICAL (Blocks therapeutic use)

Impact: Unilateral vibration (SERVER only) for first 3.7 seconds

Root Cause: MOTOR_STARTED BLE notification latency (3745 ms instead of 50 ms)

Location: src/ble_manager.c - MOTOR_STARTED characteristic write

Timeline: - 12029 ms: SERVER sends MOTOR_STARTED - 15774 ms: CLIENT receives MOTOR_STARTED - Delay: 3745 ms (3 complete motor cycles + partial)

Therapeutic Standard Violation: - EMDRIA requires bilateral alternation from session start - Unilateral vibration is contraindicated - Device does not meet safety/efficacy standards

Issue #2: CLIENT Offset Inverted During RTT Update¶

Severity: SEVERE (Blocks therapeutic use)

Impact: Antiphase operation (opposite directions) for 12+ seconds

Root Cause: RTT offset calculation sign error in time sync formula

Location: src/time_sync.c - RTT offset recalculation

Timeline: - 6064 ms: Initial offset +353346 µs (correct) - 16314 ms: RTT update inverts to -394378 µs (wrong) - 16454 ms onwards: Antiphase operation (motors opposite directions) - 37044 ms: Catch-up stops with residual -337 µs error

Therapeutic Standard Violation: - EMDRIA requires bilateral alternation throughout - Antiphase disrupts vestibuloocular coordination - Residual error prevents full recovery

How to Use These Documents¶

For Developers¶

Quick understanding: Read BOOT_ANALYSIS_SUMMARY.txt
Deep dive: Read DUAL_DEVICE_BOOT_ANALYSIS.md
Reference during coding: Use TIMELINE_TABLES.md and ANALYSIS_QUICK_REFERENCE.txt
Testing: Use debugging checklist in BOOT_ANALYSIS_SUMMARY.txt

For Code Review¶

Overview: BOOT_ANALYSIS_SUMMARY.txt sections "Root Cause Suspects"
Context: DUAL_DEVICE_BOOT_ANALYSIS.md sections "Root Cause Analysis"
Code locations: ANALYSIS_QUICK_REFERENCE.txt section "FILES TO MODIFY"
Validation: TIMELINE_TABLES.md section "Expected Behavior After Fixes"

For Testing/QA¶

Test protocol: BOOT_ANALYSIS_SUMMARY.txt section "Testing Checklist"
Expected results: TIMELINE_TABLES.md section "Expected Behavior"
Quick reference: ANALYSIS_QUICK_REFERENCE.txt section "TESTING PROTOCOL"
Verification: BOOT_ANALYSIS_SUMMARY.txt section "Device Status"

For Project Management¶

Executive summary: BOOT_ANALYSIS_SUMMARY.txt
Impact: BOOT_ANALYSIS_SUMMARY.txt section "Therapeutic Impact"
Timeline: BOOT_ANALYSIS_SUMMARY.txt section "Key Findings"
Next steps: BOOT_ANALYSIS_SUMMARY.txt section "Corrective Actions"

Key Findings Summary¶

What Works¶

BLE pairing completes successfully
Time sync handshake works (initially)
Initial motor activation logic correct
Catch-up/drift correction algorithm appropriate
Individual component testing successful

What Fails¶

Issue #1: BLE MOTOR_STARTED notification delivery extremely delayed
Issue #2: RTT offset calculation inverts sign instead of refining
Result: Device fails to meet EMDRIA bilateral alternation requirement

Combined Impact¶

Unilateral period: 3.7 seconds (Issue #1)
Antiphase period: 12+ seconds (Issue #2)
Total non-therapeutic period: 15.7+ seconds (0.8% of 20-minute session)
Verdict: Device NOT APPROVED for therapeutic testing

Critical Timestamps Reference¶

Issue #1 Timeline (Boot 1)¶

Event	Time	Significance
SERVER motor starts	12029 ms	Issue begins
CLIENT notification arrives	15774 ms	3745 ms late
Unilateral period ends	15774 ms	Bilateral begins

Issue #2 Timeline (Boot 2)¶

Event	Time	Significance
Initial offset set	6064 ms	+353 µs (correct)
RTT update occurs	16314 ms	Offset becomes -394 µs (wrong)
Antiphase operation starts	16454 ms	Motors opposite directions
Catch-up convergence stops	37044 ms	Residual -337 µs error remains

Code Locations to Review¶

Priority 1 (BLOCKING)¶

src/time_sync.c - RTT offset calculation (Issue #2)
src/ble_manager.c - MOTOR_STARTED notification (Issue #1)

Priority 2 (SUPPORTING)¶

src/motor_task.c - May need adjustment
src/time_sync.h - Offset calculation constants
src/ble_manager.h - Notification timing

Test Acceptance Criteria¶

Device is approved for therapeutic testing ONLY if ALL of the following pass:

Boot 1 Tests¶

MOTOR_STARTED arrives within 100 ms of SERVER motor start
Bilateral alternation begins by 6 second mark
No unilateral vibration period observed
Motor pattern matches LEFT-RIGHT-LEFT-RIGHT

Boot 2 Tests¶

RTT offset stays within ±100 µs of initial offset
Offset does NOT invert sign
Motors never enter antiphase operation
Residual phase error < 50 µs after convergence

Both Boots¶

Back-EMF measurements valid throughout
Motor timing matches ±50 µs precision
Bluetooth connection stable throughout
No watchdog resets or crashes

Document Statistics¶

Document	Type	Size	Purpose
DUAL_DEVICE_BOOT_ANALYSIS.md	MD	2500+ lines	Technical deep-dive
BOOT_ANALYSIS_SUMMARY.txt	TXT	300 lines	Executive summary
TIMELINE_TABLES.md	MD	800+ lines	Detailed reference tables
ANALYSIS_QUICK_REFERENCE.txt	TXT	250 lines	Pocket guide
BOOT_ANALYSIS_INDEX.md	MD	This file	Navigation/overview

Total Documentation: 3850+ lines of analysis

Next Steps¶

Immediate: Distribute to development team
Review: Code review of time_sync.c and ble_manager.c
Implementation: Fix Issue #2 (RTT offset), then Issue #1 (BLE latency)
Testing: Run full test suite with new acceptance criteria
Validation: Verify bilateral alternation from t=0 in both boots
Approval: Only approve for therapeutic testing after all tests pass

Contact & Questions¶

For questions about this analysis: - Refer to DUAL_DEVICE_BOOT_ANALYSIS.md for detailed explanations - Check TIMELINE_TABLES.md for specific timing questions - Use ANALYSIS_QUICK_REFERENCE.txt for quick lookup - Review code locations in BOOT_ANALYSIS_SUMMARY.txt

Analysis completed November 28, 2025 Device Status: NOT APPROVED FOR TESTING Required Fixes: 2 critical issues Timeline to Resolution: Estimated 1-2 days