Automatically switch Raspberry HDMI between MagicMirror2 and a desktop
Running a MagicMirror on a Raspberry Pi alongside a desktop PC? Tired of manually changing inputs when the PC boots or shuts down? Here’s a simple Bash script plus systemd service that:
- Blanks the Pi’s HDMI output whenever your desktop (IP 192.168.0.114) is up
- Restores the Pi’s HDMI when the desktop shuts down
Prerequisites
- Raspberry Pi OS with
vcgencmdworking (make sure you’re using the FKMS driver:
edit/boot/config.txtand setdtoverlay=vc4-fkms-v3d # (comment out any dtoverlay=vc4-kms-v3d)then reboot)
Source: Raspberry Pi docs –vcgencmd display_powerhttps://www.raspberrypi.com/documentation/computers/os.html#display_power-0-1-1-display - Ping utility (built into Linux) – exit code 0 means host reachable https://ss64.com/bash/ping.html
1. Create the Bash Script
Save the following as /home/pi/autoHDMI.sh and make it executable:
#!/bin/bash
# autoHDMI.sh — turn Pi HDMI off/on based on desktop presence
DESKTOP_IP="192.168.0.114" # ← your desktop’s IP
INTERVAL=10 # seconds between checks
hdmi_off=0
while true; do
if ping -c1 -W1 "$DESKTOP_IP" &>/dev/null; then
if [[ $hdmi_off -eq 0 ]]; then
/usr/bin/vcgencmd display_power 0 # blank HDMI
hdmi_off=1
fi
else
if [[ $hdmi_off -eq 1 ]]; then
/usr/bin/vcgencmd display_power 1 # restore HDMI
hdmi_off=0
fi
fi
sleep "$INTERVAL"
done
chmod +x /home/pi/autoHDMI.sh
2. Test the Commands Manually
Before automating, confirm the blank/unblank work:
# Blank the HDMI output
sudo vcgencmd display_power 0
# Restore it
sudo vcgencmd display_power 1
If you see your monitor lose signal on “0” and regain it on “1,” you’re good to go.
3. Automate with systemd
Create the service file at /etc/systemd/system/autoHDMI.service:
[Unit]
Description=Auto‑HDMI switching (Pi ↔ Desktop)
After=network-online.target
Wants=network-online.target
[Service]
User=pi
ExecStart=/home/pi/autoHDMI.sh
Restart=always
RestartSec=5
[Install]
WantedBy=multi-user.target
Enable and start it:
sudo systemctl daemon-reload
sudo systemctl enable --now autoHDMI.service
4. How It Works
- Ping check every 10 s (
ping -c1 -W1) returns exit code 0 if the desktop answers https://ss64.com/bash/ping.html - Blank: when the desktop is up, the script runs
vcgencmd display_power 0 - Restore: when the desktop goes down, it runs
vcgencmd display_power 1 - Your monitor, set to Auto‑select input, sees “no signal” on HDMI 1 and switches to your desktop (HDMI 2). When the Pi’s HDMI returns, it flips back to MagicMirror.
5. We run an X‑screen / LXDE
Source: Raspberry Pi forum thread on disabling blanking with xset (forums.raspberrypi.com)
I stopped my MagicMirror Pi’s X screen from going black by editing the LXDE autostart file and adding three xset lines.
Full file with the changes:
# /etc/xdg/lxsession/LXDE-pi/autostart
@lxpanel --profile LXDE-pi
@pcmanfm --desktop --profile LXDE-pi
point-rpi
# keep the X‑screen awake
@xset s noblank # no blanking
@xset s off # disable screensaver
Reboot and the display stays on permanently.Conclusion
With this setup, your MagicMirror display takes over whenever your desktop is off, and your PC display reclaims the screen as soon as it’s available—no manual input switching needed!
