Barometer — tdlidar_barometer

Lift the phone a flight of stairs, or feel a door slam, through air-pressure changes.

Category: Motion · Tier: Free · Needs: any iPhone (no LiDAR required)

What it does

Streams two slow channels from the phone’s air-pressure sensor: a relative altitude in metres (how far up or down the phone has moved since the app started) and the raw pressure in kilopascals. It’s sensitive enough to register a single floor of a building, an elevator ride, or the pressure pop of a closing door. Updates arrive about once a second, so treat it as a gentle, ambient input.

OSC in

address type range rate
/tdlidar/motion/altitude/relative float metres (relative) ~1 Hz
/tdlidar/motion/altitude/pressure float kPa ~1 Hz

Outputs

out1 (CHOP) — 2 channels: relative (m) and pressure (kPa). The node tile previews out1.

Parameters

par default what it does
OSC Port 9000 UDP port to listen on (match the app)

Quick start (beginner)

  1. Enable Barometer in the app’s Motion sensors.
  2. Drop the Barometer op — two near-flat lines (don’t expect motion; it’s a quiet sensor).
  3. Carry the phone up some stairs: relative climbs by roughly +3 m per floor.
  4. Wire relative into a Range CHOP (e.g. 0–10 m → 0–1) and drive a vertical gradient or a particle-system height — literally “the higher you carry the phone, the higher the visual rises”.

Advanced patterns

  • Slow-input smoothing: At ~1 Hz the signal is steppy. A Filter CHOP (or Lag with a long lag) interpolates between samples so a height-driven parameter glides instead of jumping once a second.
  • Pressure-event trigger: Subtract a slow Lag copy of pressure from the live pressure to isolate sudden bumps (a door slam, an HVAC kick), then Trigger CHOP the difference.
  • Floor detection: Quantize relative with a Math CHOP (Divide by ~3, then Floor) into integer floor numbers and use a Switch TOP to change scene per floor for a multi-storey installation.
  • Combine with motion: Pair with Acceleration/Gravity so “moving up and accelerating” reads as an elevator vs walking.

Gotchas

  • Two channels, not three — this op breaks the X/Y/Z pattern of the other motion ops. Address relative and pressure by name.
  • ~1 Hz only. It is far slower than the ≤50 Hz motion sensors; never expect responsive, frame-rate control without a Filter CHOP to interpolate.
  • relative is relative to app launch (it starts near 0), not an absolute sea-level altitude. Restart the app to re-zero.