Display Usage

The Rhino Pi IQ9N provides one HDMI 2.0 output (up to 4K@60fps) and one 4-lane MIPI-DSI display output, which can be connected to an external display and to the device's own MIPI screen respectively.

Interface Description

Interface	Quantity	Description
HDMI	1	HDMI 2.0, up to 4K@60fps
MIPI-DSI	1	4-lane MIPI-DSI, brought out through ZIF-LCM&TP

For how to connect the interfaces, see HDMI Interface.

Display Output Description

By default, the system uses MIPI-DSI as the primary screen and HDMI as the extended secondary screen. The built-in MIPI panel still reports itself as connected when no screen is attached, so the system outputs the desktop to the MIPI-DSI channel, and the desktop is not visible when only an HDMI display is connected.

The two screens are tested differently:

Test Target	MIPI Screen Connected	Configuration Change Needed
MIPI screen	Yes	No; use the default configuration
HDMI screen	No	Yes; disable the MIPI-DSI output first

Note

The vendor configuration file /etc/default/grub.d/99-dragonwing-disable-lvds.cfg only disables LVDS-1, whereas the panel on this device is actually enumerated as card0-DSI-1 (there is no LVDS interface under /sys/class/drm/). Therefore, when no MIPI screen is connected, you must additionally disable DSI-1 as described below.

Testing the MIPI Screen

1. Connect the FPC cable of the MIPI screen to the ZIF-LCM&TP connector.
2. Connect the DC power adapter; the device powers on automatically.
3. Once the system has booted, the screen shows the login screen.

Confirm that MIPI-DSI has been recognized:

cat /sys/class/drm/card0-DSI-1/status

A return of connected indicates that the MIPI screen is connected properly.

Testing the HDMI Display

When no MIPI screen is connected, you must first disable the MIPI-DSI output before the system will output the desktop to the HDMI display.

1. Use an HDMI cable to connect the device HDMI interface to the display, and switch the display input source to the corresponding HDMI channel.
2. Create the GRUB configuration file:

sudo nano /etc/default/grub.d/99-disable-dsi.cfg

3. Write the following content, then save and exit:

GRUB_CMDLINE_LINUX="${GRUB_CMDLINE_LINUX} video=DSI-1:d "

4. Update the GRUB configuration:

sudo update-grub

5. Reboot the device:

sudo reboot

6. After the reboot, the display shows the login screen.

Confirm that HDMI has been recognized:

cat /sys/class/drm/card0-HDMI-A-1/status

A return of connected indicates that the HDMI display has been recognized by the system. You can also run xrandr -q in a terminal on the device's graphical desktop to check the current resolution of the HDMI output and whether it carries the primary marker.

If the display still does not work, check whether the kernel parameter took effect:

cat /proc/cmdline

The output should contain video=DSI-1:d.

Restoring MIPI Screen Output

If you want to switch back to the MIPI screen after disabling MIPI-DSI, delete the configuration file and regenerate the GRUB configuration:

sudo rm /etc/default/grub.d/99-disable-dsi.cfg
sudo update-grub
sudo reboot

Setting Resolution and Scaling

The system runs the GNOME desktop; adjust resolution and scaling through "Settings" → "Displays".

View the current display outputs:

xrandr -q

View the kernel DRM devices:

ls /sys/class/drm/

Note

The GNOME desktop uses a Wayland session, and xrandr is provided by Xwayland, so it can only be used to query display information and cannot change the resolution. Running xrandr --output <HDMI output name> --mode 1920x1080 returns X Error of failed request: BadMatch.

FAQ

• No image on the HDMI display: confirm that the MIPI-DSI output has been disabled (see "Testing the HDMI Display") and check whether the display input source is switched to the corresponding HDMI channel.
• No image on the MIPI screen: run cat /sys/class/drm/card0-DSI-1/status to confirm that it returns connected, and check whether the FPC cable is fully inserted.
• Abnormal resolution: select a resolution supported by the display through "Settings" → "Displays".