Screen

Q1: The MIPI screen that comes with the board does not display?¶

Check whether the blue LED on the board is blinking. If it is not blinking, the system has not booted properly. No backlight: Have you flashed the standard image from our cloud storage? Check whether the FPC cable is loose at both ends or connected backwards. Backlight on but no image: Check whether the wiring on the back of the adapter board is correct. If you compiled the SDK yourself, you need to uncomment the corresponding screen in the device tree or compile a multi‑screen auto‑detection image.
Check that the FPC cable is fully inserted and locked, and that the gold fingers are not dirty or scratched.
The K7 V1.4 and earlier versions do not have the multi‑screen auto‑detection feature. You need to flash the dedicated image for your screen model (the supported screen model is usually indicated in the image filename).
Some MIPI screens require an adapter board. Verify that the wiring on the back of the adapter board is correct (e.g., voltage jumper settings, I2C address selection, etc.) and that there are no cold or shorted solder joints.
Connect an HDMI display. If HDMI works but the MIPI screen does not, the system has booted correctly and the issue is likely with the MIPI screen hardware connection or its configuration.

If the pinouts do not match, you can design an adapter board to solve the hardware connection issue. However, you still need to adapt the screen driver in the SDK — it is not plug‑and‑play.
The adapter board only remaps the physical pins (pin‑to‑pin mapping), allowing the board's MIPI DSI signals to reach the screen connector correctly. It does not change the electrical characteristics or communication protocol.
Each MIPI screen has its own initialisation code, timing parameters, and voltage configuration (LCD voltage). These must be configured in the SDK's device tree file (.dts) and screen driver code. The specific parameters are usually provided by the screen manufacturer in the datasheet.

The theoretical maximum is 30 cm. Beyond this length, signal interference increases. Cables longer than 30 cm may work, but you will need to verify stability yourself.
MIPI DSI high‑speed differential signals attenuate significantly over FPC cables longer than 30 cm, which can cause flickering, noise, streaks, or even no display.
If you need to place the screen further away, consider using a MIPI‑to‑LVDS/eDP adapter board with shielded cables to extend the transmission distance (typically up to 50–100 cm), or use an external HDMI display.

Ubuntu desktop: use xrandr to list supported display modes, then xrandr --output HDMI-1 --mode 1920x1080 to change. Android: use adb shell wm size and adb shell wm density to set.
The resolution you set must be within the display controller's capabilities; unsupported settings will not take effect.

For Android, extended display is implemented at the application layer. You can refer to the RK development documentation in the SDK. For Linux, you can configure it in the display settings.
On Android, extended display is implemented via the Presentation API or DisplayManager. The secondary display defaults to extended mode. Application developers can use DisplayManager.getDisplays() to enumerate all displays and output specific content to a target screen.
On Linux, use xrandr --output HDMI-1 --mode 1920x1080 --right-of DSI-1 to set up an extended display with HDMI to the right of the MIPI screen. You can also drag and arrange displays in the desktop environment's display settings.