Implement DDM Telemetry Logging and CSV Export

[josiah-nelson]

Overview

Implement Digital Diagnostics Monitoring (DDM) telemetry capture and historical logging with CSV export functionality. This allows users to monitor and track SFP module health metrics over time.

Current State

• Basic DDM line detection exists (/ddm:/i.test())
• DDM samples are captured to ddmSamples array but not persisted
• No parsing of DDM values
• No UI for viewing or exporting DDM data
• TODO comment: "Accumulate DDM samples for CSV export (future)"

Background: SFP DDM/DOM

Digital Diagnostics Monitoring (DDM), also called Digital Optical Monitoring (DOM), provides real-time monitoring of SFP parameters:

• Temperature (°C)
• Voltage (V)
• TX Bias Current (mA)
• TX Power (dBm)
• RX Power (dBm)

These values are typically found in EEPROM address A2h (bytes 96-105) per SFF-8472 spec.

Proposed Solution

Phase 1: DDM Parsing

• Parse DDM telemetry from BLE notifications
• Extract numeric values for each metric
• Store with timestamp in structured format
• Handle units and scaling per SFF-8472 spec

Phase 2: In-Memory Storage & UI Display

• Maintain rolling buffer of recent DDM samples (e.g., last 1000)
• Add "DDM Monitor" section to UI showing:
  • Current values (live update)
  • Min/Max values
  • Simple line charts (optional, using Chart.js or similar)
• Show module health status (within spec / warning / alarm)

Phase 3: CSV Export

• Export time-series DDM data to CSV format
• Include columns: timestamp, temperature, voltage, tx_bias, tx_power, rx_power
• Allow filtering by date range
• Support export of all modules or selected module

Phase 4: Backend Persistence (Optional)

• Add backend table for DDM samples
• API endpoints:
  • POST /api/ddm - Store DDM sample
  • GET /api/ddm/{module_id} - Retrieve samples for module
  • GET /api/ddm/export.csv - Export all DDM data
• Implement data retention policy (e.g., 30 days)

Implementation Tasks

• Research SFP Wizard's DDM broadcast format from BLE logs
• Implement DDM message parser
• Create DDM data structure/class
• Add rolling buffer for DDM samples (in-memory)
• Create "DDM Monitor" UI section
• Implement real-time value display
• Add CSV export function (frontend)
• Add date range picker for export filtering
• Test with live DDM data from device
• Document DDM format in code comments
• (Optional) Add backend persistence
• (Optional) Add simple charting for trends

Acceptance Criteria

• DDM telemetry is correctly parsed from BLE notifications
• Current DDM values are displayed in the UI
• Users can export DDM history to CSV file
• CSV format is compatible with Excel/Google Sheets
• Proper handling when DDM is not available (older SFP modules)
• Documentation explains DDM feature and interpretation

Technical Notes

DDM Format Example (hypothetical)

ddm: temp=45.2°C vcc=3.3V tx_bias=30.5mA tx_pwr=-2.3dBm rx_pwr=-3.1dBm

CSV Format

timestamp,module_id,module_name,temperature_c,voltage_v,tx_bias_ma,tx_power_dbm,rx_power_dbm
2025-11-01T12:00:00Z,1,Cisco 10G,45.2,3.3,30.5,-2.3,-3.1

Performance Considerations

• Use circular buffer to limit memory usage
• Throttle UI updates (max 1 update per second)
• CSV generation should be non-blocking

Dependencies

None - standalone feature

Priority

Medium - Valuable diagnostic feature but not critical for basic operation

Labels

enhancement, frontend, backend, feature