LCD

The RK3568 is equipped with four display output interfaces, namely HDMI, MIPI, LVDS, and EDP. It supports a maximum of three simultaneous display outputs.

1. Introduction to Display Interface Resources

RK3568

The RK3568 has three VP nodes, and each VP node can be connected to a display. The corresponding relationships are shown in the following table:

VP Number	Supported Display Interfaces	Maximum VP Resolution
VP0	MIPI0 / MIPI1 / HDMI / EDP	4096x2304@60Hz
VP1	MIPI0 / MIPI1 / LVDS / HDMI / EDP	2048x1536@60Hz
VP2	LVDS / RGB	1920x1080@60Hz

The pins of the MIPI0 and LVDS interfaces conflict, so only one can be selected.

The VP2 node only supports LVDS/RGB. Therefore, one of the three displays must be LVDS (the RGB interface is not led out) in a triple-screen display setup.

Display Interface	Maximum Display Resolution	Format
HDMI	4096x2160@60Hz	RGB/YUV420 10Bit
MIPI	1920x1080@60Hz	RGB 8Bit
Dual MIPI	2560x1440@60Hz	RGB 8Bit
LVDS	1280x800@60Hz	RGB 8Bit
EDP	2560x1600@60Hz	RGB 10Bit
RGB	1920x1080@60Hz	RGB 8Bit

2. Single Display Driver Configuration

Display configuration mainly involves modifying the device tree LCD configuration file. The device tree LCD configuration directory for the RK3568 is as follows:

$ vim kernel/arch/arm64/boot/dts/rockchip/rk3568-kickpi-k1.dtsi //linux
$ vim kernel-5.10/arch/arm64/boot/dts/rockchip/rk3568-kickpi-k1.dtsi //android

// LCD
#include "rk3568-kickpi-lcd-hdmi.dtsi"
//#include "rk3568-kickpi-lcd-edp-15.6-1920-1080.dtsi"
//#include "rk3568-kickpi-lcd-mipi0-10.1-800-1280.dtsi"
//#include "rk3568-kickpi-lcd-mipi1-10.1-800-1280.dtsi"
//#include "rk3568-kickpi-lcd-lvds-7-1024-600.dtsi"

The rk3568-kickpi-lcd-hdmi.dtsi file needs to be enabled by default.

If there are problems with display debugging, you can contact after-sales for technical support.

MIPI

The RK3568 has two MIPI LCD interfaces, namely MIPI0 and MIPI1. Among them, MIPI0 is multiplexed with LVDS.

For the MIPI0 interface, refer to rk3568-kickpi-lcd-mipi0-10.1-800-1280.dtsi. For the MIPI1 interface, refer to rk3568-kickpi-lcd-mipi1-10.1-800-1280.dtsi.

LVDS

For the LVDS interface, refer to rk3568-kickpi-lcd-lvds-7-1024-600.dtsi.

EDP

For the EDP interface, refer to rk3568-kickpi-lcd-edp-15.6-1920-1080.dtsi.

3. Multi-Screen Display System Configuration

In a multi-screen display solution, pay attention to the following when selecting LCD parameters:

It is recommended to choose displays with the same aspect ratio; otherwise, the picture may be stretched or have black borders.

Kernel Device Tree Configuration

$ vim kernel/arch/arm64/boot/dts/rockchip/rk3568-kickpi-k1.dtsi

// Triple LCD
//#include "rk3568-kickpi-triple-lcd-hdmi-mipi1-lvds.dtsi"
//#include "rk3568-kickpi-triple-lcd-edp-mipi1-lvds.dtsi"

On the basis of completing single-screen debugging, refer to the above-provided multi-screen device tree configuration files.

Android Multi-Screen Configuration

• Use DSI as the primary screen and HDMI-A as the secondary screen

PRODUCT_PROPERTY_OVERRIDES += vendor.hwc.device.primary=DSI
PRODUCT_PROPERTY_OVERRIDES += vendor.hwc.device.extend=HDMI-A

• Use DSI/eDP as the primary screen and LVDS/HDMI-A as the secondary screen

PRODUCT_PROPERTY_OVERRIDES += vendor.hwc.device.primary=DSI,eDP
PRODUCT_PROPERTY_OVERRIDES += vendor.hwc.device.extend=LVDS,HDMI-A

4. Single Touchscreen Driver Configuration

Take GT9XX as an example.

Driver Porting

Port the driver provided by the manufacturer to the SDK directory and modify the compilation files.

Copy the driver files to the touch driver folder $(SDK_DIR)\kernel-5.10\drivers\input\touchscreen.

Modify the kconfig file by adding the following:

config TOUCHSCREEN_GT9XX
	tristate "GT9XX touchscreens support"

Modify the Makefile by adding the following:

obj-$(CONFIG_TOUCHSCREEN_GT9XX)		+= gt9xx/

Add CONFIG_TOUCHSCREEN_GT9XX=y to the kernel configuration.

The kernel configuration file is, for example, arch/arm64/configs/rockchip_defconfig. For different versions of defconfig, please find the corresponding version file in the Git history.

Kernel Device Tree Configuration

i2c_gt9xx configuration:

&i2c1 {
	status = "okay";
	gt9xx:gt9xx@5d {
		compatible = "goodix,gt9xx";
		status = "okay";
		reg = <0x5d>;

		gtp_resolution_x = <1024>;
		gtp_resolution_y = <600>;
		gtp_int_tarigger = <1>;
		gtp_change_x2y = <0>;
		gtp_overturn_x = <0>;
		gtp_overturn_y = <0>;
		gtp_send_cfg = <1>;
		gtp_touch_wakeup = <1>;
		goodix_rst_gpio = <&gpio0 RK_PB6 GPIO_ACTIVE_HIGH>;
		goodix_irq_gpio = <&gpio3 RK_PA3 IRQ_TYPE_LEVEL_LOW>;
		pinctrl-names = "default";
		pinctrl-0 = <&touch3_gpio>;

		goodix,cfg-group0 = [
			4B 00 04 58 02 01 0D 00 01 08
			28 05 50 32 03 05 00 00 00 00
			00 00 00 00 00 00 00 8B 2A 0C
			17 15 31 0D 00 00 02 BA 03 2D
			00 00 00 00 00 03 00 00 00 00
			00 0F 41 94 C5 02 07 00 00 04
			9B 11 00 77 17 00 5C 1F 00 48
			2A 00 3B 38 00 3B 00 00 00 00
			00 00 00 00 00 00 00 00 00 00
			00 00 00 00 00 00 00 00 00 00
			00 00 00 00 00 00 00 00 00 00
			00 00 02 04 06 08 0A 0C 0E 10
			12 14 16 18 FF FF 00 00 00 00
			00 00 00 00 00 00 00 00 00 00
			00 00 00 02 04 06 08 0A 0C 0F
			10 12 13 16 18 1C 1D 1E 1F 20
			21 22 24 FF FF FF FF FF 00 00
			00 00 00 00 00 00 00 00 00 00
			00 00 00 00 B6 01
		];
	};
};

Rotating the Touch Direction

Adjust the touchscreen direction based on the device tree. The following directions are only applicable to the GT9XX driver.

0 degrees (default)

gt9xx:gt9xx@5d {
	gtp_change_x2y = <0>;		
	gtp_overturn_x = <0>;
	gtp_overturn_y = <0>;
};

90 degrees

gt9xx:gt9xx@5d {
	gtp_change_x2y = <1>;
	gtp_overturn_x = <1>;
	gtp_overturn_y = <0>;
};

180 degrees

gt9xx:gt9xx@5d {
	gtp_change_x2y = <0>;
	gtp_overturn_x = <0>;
	gtp_overturn_y = <1>;
};

270 degrees

gt9xx:gt9xx@5d {
	gtp_change_x2y = <0>;
	gtp_overturn_x = <1>;
	gtp_overturn_y = <0>;
};

5. Multi-Screen Touch System Configuration

Kernel Device Tree Configuration

I2C + I2C

Android Single-Screen Touch Configuration

• Android 13.0

Disable touch on the secondary screen. Whether it is an external or internal device, the touch function only works on the primary screen.

$ vim frameworks/native/services/inputflinger/reader/EventHub.cpp

    // Determine whether the device is external or internal.
    if (isExternalDeviceLocked(device)) {
-        device->classes |= INPUT_DEVICE_CLASS_EXTERNAL;
+        //device->classes |= INPUT_DEVICE_CLASS_EXTERNAL;
    }

Android Multi-Screen Touch Configuration

• Determine the device name

$ vim frameworks/native/services/inputflinger/reader/EventHub.cpp

bool EventHub::isExternalDeviceLocked(Device* device) {
+	const char *I2C_DEVICE_NAME = "generic ft5x06 (79)";
+	ALOGE("input deviceis '%s' ",device->identifier.name.c_str());
+	if (strcmp(device->identifier.name.c_str(), I2C_DEVICE_NAME) == 0) {
+		return true;
+	}

	if (device->configuration) {
	bool value;
}

• Add an IDC configuration file