feat: Logging and diagnostics

[cursor]

Feature Description

Implement comprehensive logging and diagnostic features.

Firmware Logging

Event Types

• Startup/Reset events
• Fan state changes (connected/disconnected)
• USB connection/disconnection
• Configuration changes
• Errors and warnings
• Temperature readings

Storage

• Ring buffer in RAM (last 100 events)
• Optional: Flash storage (persistent log)
• Timestamps using RTC or uptime

Access

pico-fan-ctl log show
pico-fan-ctl log clear
pico-fan-ctl log export > fanlog.txt

Diagnostics

Self-Test

pico-fan-ctl diag self-test

Tests:

• PWM output verification
• Tachometer input test
• RGB LED test pattern
• USB communication test
• Sensor communication (if present)
• Voltage level checks

Statistics

• Uptime
• Total runtime hours per fan
• Fan start/stop cycles
• Error count
• USB reconnection count
• Temperature history (min/max)

Debug Mode

• Verbose USB reports
• Continuous monitoring
• Performance metrics
• Memory usage

Linux Integration

syslog

• Critical events to syslog
• journalctl -u pico-fan-hub

hwmon

/sys/class/hwmon/hwmonX/
  fan1_alarm    # Fan failure status
  intrusion0    # Error conditions

Priority

Medium - Important for troubleshooting