IoTGateway/BSP/Android/Gettingstarted/How to set HDMI for rk
From ESS-WIKI
If you want to use HDMI 4K resolution, please modify the file /kernel_imx/arch/arm/boot/dts/rk3288-rsb4680-a1.dts,set ENABLE_4K_DISPLAY to 1
HDMI resolution setting method:Starting Android,Entry Settings->HDMI->HDMI Resolution