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CSI Motion Monitor

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Just Call Me Koko edited this page Oct 13, 2026 · 1 revision

CSI Motion Monitor

CSI stands for Channel State Information. Wi-Fi receivers estimate how each subcarrier traveled from an access point; movement changes the reflected and obstructed signal paths, and Marauder turns those changes into a motion score.

CSI Motion Monitor is passive. It does not transmit attacks, identify a person, produce an image, or determine an exact location. It reports changes in the radio environment around the selected access point.

Start a Session on a Display

  1. Place the Marauder where it will remain during monitoring.
  2. Run an AP scan.
  3. Open WiFi > Sniffers > CSI Motion Monitor.
  4. Select an access point. Marauder stays on that AP's channel and accepts CSI from its BSSID.
  5. Keep the room and Marauder still during the 30-second calibration.

The selected AP must continue transmitting packets. A busier AP generally provides a higher sample rate and more responsive detection than an idle AP.

Read the Display

The layout is scaled for the display available on each hardware target. Small screens retain the graph and most important telemetry while shortening labels.

  • Motion: fused 0-100 disturbance score.
  • Reliability: confidence based on sample cadence, RSSI stability, queue loss, and calibration state.
  • Amp: amplitude-variation contribution.
  • Phase: relative phase-residual contribution.
  • Corr: change in the subcarrier-amplitude shape.
  • Rate: accepted CSI samples per second.
  • Drop: samples discarded because the fixed callback queue was full.
  • State: CALIBRATING, LOW DATA, STILL, POSSIBLE, or MOTION.

The graph plots the recent fused motion score. Gaps indicate missing or low-confidence data.

Controls vary by hardware:

  • Button-based builds use the displayed recalibrate and stop controls. Common mappings are Up to recalibrate and Center to stop.
  • Touchscreen builds use the upper portion of the screen to recalibrate and the lower portion to stop.
  • Headless builds use the serial commands below.

Headless and Serial Use

Serial remains at 115200 baud. To start from the CLI:

sniffbeacon
stopscan
list -a
csimotion start <AP index>

While monitoring, Marauder prints one readable status line per second:

CSI motion | state=STILL | motion=4 | reliability=96 | amp=3 | phase=5 | corr=2 | rate=38/s | dropped=0 | calibration=100% | AP="Example" | channel=6

Available controls:

csimotion status
csimotion recalibrate
stopscan

The serial stream contains processed motion telemetry, not raw CSI samples.

Placement and Calibration

Motion does not have to occur on a perfect straight line between the Marauder and router. CSI responds to multipath propagation, so people and objects can affect reflected paths around a room. Detection strength depends on placement, walls, antenna orientation, AP traffic, interference, distance, and the movement's relationship to useful signal paths.

For best results:

  • Keep both the Marauder and AP stationary.
  • Place them so the area of interest lies between or near useful radio paths.
  • Prefer an active AP with a steady sample rate.
  • Recalibrate after moving either endpoint or making a major change to the room.
  • Compare still and walking scores in the actual installation before relying on state changes.

Calibration adapts to each placement, but it cannot compensate for very sparse packets or a weak/unstable signal. On ESP32-C6, capture is deliberately restricted to compatible legacy frames so motion windows do not mix different CSI vector layouts; some modern or quiet APs may therefore provide a lower sample rate.

Privacy

The selected AP name is shown on the CSI screen and included in serial telemetry. Enable the Censor setting before recording a display if nearby identifiers should not be visible. Censor affects the display only; it does not sanitize serial output or capture files.

Limitations

  • CSI motion detection is an environmental change detector, not a security alarm or occupancy guarantee.
  • A fan, pet, moving door, shifting object, or endpoint movement can produce motion evidence.
  • Movement outside the strongest radio paths may produce little evidence.
  • Different ESP32 families expose CSI differently, so cadence and score ranges can vary by target and AP.
  • Stop the monitor normally before starting another Wi-Fi function so the CSI receiver can release the radio cleanly.

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