vmi-reverse-engineering

name	vmi-reverse-engineering
description	This skill should be used when the user asks to "reverse engineer VMI", "capture BLE traffic", "analyze VMI protocol", "control VMI app via ADB", "pull btsnoop logs", or discusses Ventilairsec device protocol analysis.

VMI App Reverse Engineering

Control the Ventilairsec VMI+ app via ADB to capture and analyze BLE protocol traffic.

Quick Start

# 1. Enable BT snoop logging (one-time setup)
./scripts/capture/vmictl.py btsnoop-enable

# 2. Connect to device
./scripts/capture/vmictl.py connect

# 3. Start capture session
SESSION=$(./scripts/capture/vmictl.py session-start my_session)
# Navigate, take checkpoints, record values, then end session
./scripts/capture/vmictl.py session-end "$SESSION"

For phone setup, ADB connection, BT snoop logging details, and troubleshooting, see playbook.md section 1.

App Control Commands

Connection

Command	Description
connect	Full sequence: launch → scan → pair → dismiss update dialog
launch	Just launch the app
stop	Force-stop the VMI+ app
vmci	Tap VMCI device type
pair	Tap PAIR on scan results
dismiss	Dismiss update dialog

Navigation (from home screen)

Command	Description
menu	Open hamburger menu
config	Menu → Configuration
simplified	Configuration → Simplified
maintenance	Menu → Maintenance
sensors	Menu → Sensor management

Maintenance Screens

Command	Description
available-info	Maintenance → Available info
equipment-life	Available info → Equipment life
measurements	Available info → Measurements (temp/humidity)
measurements-full	Full nav: home → menu → maintenance → available info → measurements
diagnostic	Available info → Diagnostic

Configuration Screens

Command	Description
special-modes	Configuration → Special modes (holiday, etc.)
special-modes-full	Full nav from home to Special modes
time-slots	Configuration → Time slot configuration

Schedule Controls (from Time Slot Configuration)

Command	Description
schedule-edition	Select EDITION tab
schedule-planning	Select PLANNING tab
schedule-hour <0-23>	Tap hour row in schedule table

Sensor Selection (from Sensor management)

Command	Description
sensor-probe1	Select Probe 1 (outlet)
sensor-probe2	Select Probe 2 (inlet)
sensor-remote	Select Remote Control

Fan Control (from home screen) ⚡

Command	Description
fan-min	Set to LOW (131 m³/h)
fan-mid	Set to MEDIUM (164 m³/h)
fan-max	Set to HIGH (201 m³/h)
boost	Activate BOOST mode
preheat-toggle	Toggle preheat ON/OFF
preheat-temp <n>	Set preheat temperature (12-18 or "mini")
summer-limit <n>	Set summer limit temperature (22-37)

Holiday Mode (from Special modes screen) ⚡

Command	Description
holiday-toggle	Toggle Holiday mode ON/OFF
holiday-days <n>	Set Holiday duration to n days

⚡ = modifies VMI state. These commands (plus airflow, airflow-min, airflow-max, preheat-temp, summer-limit, firmware-update) are automatically logged to data/captures/vmi_actions.log. If a capture session is active, an automatic checkpoint (screenshot + timestamp) is also taken — no need to call session-checkpoint manually.

Utility

Command	Description
screenshot [file]	Take screenshot
scroll	Scroll down
back	Press back button
ui	Dump UI hierarchy (XML)
resolution	Show detected resolution
battery	Show phone battery level and charging status

Bluetooth Capture

Command	Description
btsnoop-enable	Enable FULL BT snoop logging
btstart	Enable logging (basic, may be filtered)
btpull	Pull btsnoop logs via bugreport
session-start <name>	Start capture session, outputs directory path
session-checkpoint <dir> [note]	Take timestamped screenshot with optional note
session-end <dir>	End session, pull btsnoop logs
collect-sensors [--force]	Build timestamped UI+packet evidence session for sensor analysis
should-collect	Check if sensor collection is due

Screen Hierarchy

HOME (fan control buttons)
├── menu
│   ├── Configuration
│   │   ├── Simplified (airflow slider)
│   │   ├── Special modes (holiday, night vent, fixed airflow)
│   │   └── Time slot configuration
│   ├── Maintenance
│   │   └── Available info
│   │       ├── Equipment life (filter days, serial)
│   │       ├── Instantaneous measurements (temp/humidity)
│   │       └── Diagnostic (component health)
│   └── Sensor management (probe selection)

Capture Session Workflow

# 1. Start session (outputs directory path)
SESSION=$(./scripts/capture/vmictl.py session-start humidity_test)

# 2. Navigate to screen, take checkpoint (outputs screenshot path)
SCREENSHOT=$(./scripts/capture/vmictl.py session-checkpoint "$SESSION")

# 3. Read the screenshot to see values, then append to checkpoints.txt

# 4. State-modifying commands auto-checkpoint when a session is active:
./scripts/capture/vmictl.py fan-max  # auto-checkpoint with note "action=fan-max"

# 5. End session and pull btsnoop logs
./scripts/capture/vmictl.py session-end "$SESSION"

After each checkpoint, append observed values to $SESSION/checkpoints.txt:

remote_temp=19
remote_humidity=55
probe1_temp=16
probe1_humidity=71
notes=after switching to Probe1 sensor

Note: State-modifying commands (fan-*, boost, preheat-toggle, preheat-temp, airflow*, holiday-*, firmware-update) automatically create a checkpoint when a session is active. You only need manual session-checkpoint calls for read-only observations (navigating to a screen to record displayed values).

Packet Analysis

# Basic extraction
python scripts/capture/extract_packets.py session/btsnoop.log

# With checkpoint correlation
python scripts/capture/extract_packets.py session/btsnoop.log \
    --checkpoints session/checkpoints.txt --window 10

# Export status packets as hex
python scripts/capture/extract_packets.py session/btsnoop.log --status-hex

For packet type reference, field offsets, and encoding details, see protocol.md.

Instructions for Claude

When helping with reverse engineering:

1. Before capturing: Ensure BT snoop is enabled with btsnoop-enable
2. For new protocol fields: Use capture session with checkpoints
3. Record values: Read each checkpoint screenshot, append values to checkpoints.txt
4. Compare packets: Use --checkpoints flag to correlate bytes with app values
5. Navigation: Follow screen hierarchy - can't jump directly to submenus
6. Verify results: Check screenshots in session directory

Phone Battery Monitoring

The Fairphone used for reverse engineering is not plugged in and will eventually run out of battery. The vmictl script automatically checks battery level every 5 minutes and prints a warning to stderr when it's low.

You MUST relay battery warnings to the user. When you see output containing BATTERY WARNING or BATTERY CRITICAL from any vmictl command:

• WARNING (<= 20%): Immediately tell the user: "The phone battery is at X% — it should be charged soon to avoid losing the session."
• CRITICAL (<= 10%): Stop what you are doing and alert the user: "The phone battery is critically low (X%). It needs to be charged NOW or it will shut off and we'll lose BLE connectivity."

You can also check manually at any time with ./scripts/capture/vmictl.py battery.

Opportunistic Data Collection

At the start of any VMI debugging session, run the sensor collection command:

./scripts/capture/vmictl.py collect-sensors

This command:

1. Checks if 15+ minutes have passed since last collection (skip if too recent)
2. Navigates to Instantaneous Measurements screen
3. Takes a screenshot and pulls btsnoop logs
4. Extracts packet byte values and displays them for comparison

Use --force to collect even if less than 15 minutes have passed.

After running, read the screenshot and compare app values to packet bytes. If values differ, add a timestamped note in the current investigation issue/logbook.

Field	App Screen	Packet Location
Remote temp	Remote Control → Temperature	SCHEDULE (0x02) byte 11
Remote humidity	Remote Control → Humidity	SCHEDULE (0x02) byte 13
Probe 1 temp	Probe N°1 → Temperature	PROBE_SENSORS (0x03) byte 6
Probe 1 humidity	Probe N°1 → Humidity	PROBE_SENSORS (0x03) byte 8
Probe 2 temp	Probe N°2 → Temperature	PROBE_SENSORS (0x03) byte 11

Data is stored persistently in data/captures/ (gitignored, survives reboots).