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HDMI Display

This guide explains how to connect a display to the board, configure it where needed, verify that it is detected, and render content on it.

The Grinn AstraOneSBC-1680 drives an external monitor over HDMI. The transmitter supports up to 2160p60 with HDR10+, HDCP 2.3, and CEC. No Device Tree Overlay or image extension is needed, because the interface is enabled in the default image.

note

HDMI is the only display output on this board. The FPC connector next to it is the MIPI CSI camera input and cannot drive a display.

Connect the Display​

The board exposes a mini-HDMI connector, so a cable or adapter that matches that connector on one end and the monitor on the other end is required.

  1. Plug the cable into the mini-HDMI connector.
  2. Connect the other end to the monitor and select the matching input source on it.
  3. Power on the board.
note

The interface is hot-pluggable, so the monitor can also be attached while the board is running. Connecting it before power-on is still recommended, because the compositor then picks up the monitor's preferred resolution on the first start.

Verify the Display​

On the host, enter the target shell:

adb shell

In the target shell, list the DRM connectors and their status:

for status in /sys/class/drm/card*-*/status; do
  connector=${status%/status}
  printf '%s: %s\n' "${connector##*/}" "$(cat "$status")"
done

The connector the display is attached to has to be reported as connected, for example:

card0-HDMI-A-1: connected

If the connector is missing or reported as disconnected, check the connection as described above.

Keep this target shell open for the examples below.

Use the Display​

The image runs a Wayland / Weston compositor by default, so the desktop appears on the display as soon as it is detected. The following steps run in the target shell.

Point the Wayland clients at the running compositor first:

WAYLAND_SOCKET=$(find /run/user -mindepth 2 -maxdepth 2 -type s -name 'wayland-*' -print -quit)

export XDG_RUNTIME_DIR="${WAYLAND_SOCKET%/*}"
export WAYLAND_DISPLAY="${WAYLAND_SOCKET##*/}"

Then render a test pattern full screen:

gst-launch-1.0 -v videotestsrc \
! video/x-raw,format=NV12 \
! waylandsink fullscreen=true

A color bar pattern covering the whole display confirms that the pipeline works end to end. Press Ctrl+C in the shell to stop it.

tip

If the monitor stays blank, try a different cable or adapter first. Passive mini-HDMI adapters are a common source of link problems at 4K resolutions.