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Compiled Android system, transplanted to the board, found that the system is vertical screen, and we need the system landscape, you need to modify the value ro.sf.hwrotation, usually 0,90,180,270 ,. The system will be based on the value of the corresponding counter-clockwise rotation angle, you can become what we need, ro.sf.hwrotation device in the system / rockchip / RK3288 /system.prop (exact location depends on your chip). Ro.sf.hwrotation will see the value of our revised in build.prop under the system directory after recompiling, this time system.img then downloaded to the board can implement the system landscape.