Presence‑Aware Wall Panel on Raspberry Pi (X11, Bookworm)

This Gist documents a complete, reproducible setup for a Raspberry Pi–driven wall touchscreen that:

• Turns the monitor off after N minutes of no activity.

• Turns the monitor on when:

  • The camera detects motion nearby, or
  • The user touches/moves the mouse/keyboard.

• Re‑applies touchscreen rotation/calibration every time the display wakes.

Assumptions:

• Raspberry Pi OS Bookworm.
• Running an X11 session (Openbox/LXDE or similar).
• A USB webcam (or any V4L2 camera) visible as /dev/video0.
• Monitor supports DPMS standby (most do).

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0) Packages you need

sudo apt update
sudo apt install motion x11-xserver-utils xprintidle v4l-utils

• motion: detects movement using the camera.
• x11-xserver-utils: provides xset for DPMS control.
• xprintidle: reads the X11 idle timer (touch/KB/mouse).
• v4l-utils: camera debugging tools.

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1) Confirm X11 + DPMS control works

1.1 Verify you are on X11

echo $XDG_SESSION_TYPE
# should print: x11

1.2 Enable Screen Blanking (so DPMS extension exists)

On Bookworm/X11, DPMS may be disabled until Screen Blanking is enabled.

sudo raspi-config
# Display Options -> Screen Blanking -> Enable

Reboot once after changing this.

1.3 Test DPMS force commands

Run these in your desktop session:

export DISPLAY=:0
xset dpms force off
sleep 2
xset dpms force on

If force works, you’re good.

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2) Disable OS idle blanking timers (optional but recommended)

We want our daemon to decide when to sleep, not the desktop’s own timers.

Run once (and later add to autostart if desired):

export DISPLAY=:0
xset s off
xset s noblank
xset -dpms
xset dpms 0 0 0

Notes:

• This disables timeouts, but DPMS can still be forced on/off by the daemon.

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3) Camera sanity check

Confirm your camera is detected:

v4l2-ctl --list-devices

You should see something like:

• /dev/video0

If your camera appears under a different node, update Motion’s video_device accordingly.

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4) Create a Motion hook for presence timestamps

4.1 Hook script

This script writes a fresh epoch timestamp every time Motion sees movement.

sudo tee /usr/local/bin/presence_event.sh >/dev/null <<'EOF'
#!/bin/bash
# Called by motion when movement is detected.
# Write a timestamp to a tmp file read by the presence daemon.
echo "motion $(date +%s)" > /tmp/presence_event
EOF

sudo chmod +x /usr/local/bin/presence_event.sh

4.2 Motion config

Overwrite /etc/motion/motion.conf with the file in the companion Gist motion.conf (see files list).

Key requirements inside the config:

• daemon off (so systemd keeps it running)
• video_device /dev/video0
• on_motion_detected /usr/local/bin/presence_event.sh
• outputs disabled (no photos/movies)

Restart Motion:

sudo systemctl enable motion
sudo systemctl restart motion
sudo systemctl status motion --no-pager -l

Expect:

• Active: active (running)

4.3 Verify the hook fires

Move in front of the camera, then:

cat /tmp/presence_event

Example:

motion 1763827202

If this file doesn’t update while you move, Motion sensitivity needs tuning (section 7).

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5) Touchscreen rotation script

If you already have a working rotation/calibration script, keep using it. This setup assumes it is located at:

~/auto-rotate.sh

Your daemon will re‑run this script on every wake.

If your script name/path differs, update the ROTATE_SCRIPT variable in presence_panel.py.

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6) Presence daemon (DPMS + camera + X idle)

Place the Python daemon from the companion file presence_panel.py into:

~/presence_panel.py
chmod +x ~/presence_panel.py

Manual test:

python3 ~/presence_panel.py

Behavior:

• If the monitor is off and motion is detected, DPMS wakes it.
• If someone taps/moves input, xprintidle resets the timer even if the camera misses it.
• After wake, ~/auto-rotate.sh runs so touch calibration matches rotation.
• Screen turns off after OFF_TIMEOUT seconds of no motion/input.

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7) Fine‑tuning Motion sensitivity

Most false positives/negatives are fixed by adjusting a small set of Motion parameters.

Edit:

sudo nano /etc/motion/motion.conf
sudo systemctl restart motion

7.1 Most important settings

Setting	What it does	How to tune
threshold	How much change counts as motion	Increase to reduce false positives; decrease if it misses people. Start around 1500.
noise_level	Filters low‑level pixel noise	Increase if flickering light triggers motion.
event_gap	Seconds without motion before an event ends	Increase if you want fewer start/stop events. Doesn’t affect wake timing much if you use on_motion_detected.
width/height	Detection resolution	Lower = less CPU and less sensitivity to small changes. 640×480 is a good start.
framerate	Detection FPS	Lower = less CPU. 5 FPS is usually enough for presence.

7.2 Practical tuning workflow

1. Watch logs live:

   sudo journalctl -u motion -f

2. Walk in/out, note triggers.

3. Change one parameter.

4. Restart Motion.

5. Repeat.

7.3 Common problems

• Triggers from TV/windows: raise threshold, raise noise_level, or physically aim the camera away.
• Misses slow movement: lower threshold, increase framerate slightly.
• Too much CPU: lower width/height, lower framerate, disable streaming (already disabled here).

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8) Autostart the presence daemon (user systemd)

Create the service:

mkdir -p ~/.config/systemd/user
nano ~/.config/systemd/user/presence-panel.service

Paste:

[Unit]
Description=Presence-based panel control (X11)

[Service]
ExecStart=/usr/bin/python3 %h/presence_panel.py
Restart=on-failure

[Install]
WantedBy=default.target

Enable/start:

systemctl --user daemon-reload
systemctl --user enable presence-panel
systemctl --user restart presence-panel
systemctl --user status presence-panel --no-pager -l

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9) What to do if something breaks

Motion running but no /tmp/presence_event

• Ensure hook lines are not commented.

• Confirm Motion is reading /etc/motion/motion.conf.

• Check for script exec errors in logs:

  sudo journalctl -u motion --no-pager | tail -n 120

Screen never wakes on motion

• Ensure /tmp/presence_event timestamp changes when you move.

• Confirm daemon is running:

  systemctl --user status presence-panel

Touch mapping wrong after wake

• Verify your ~/auto-rotate.sh works by running it manually.
• Ensure the path is correct in presence_panel.py.

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Companion files in this Gist

• motion.conf — full Motion configuration used here.
• presence_panel.py — full presence daemon.
• presence-panel.service — systemd user unit.