04 MIPI screen detection case

Case Introduction

This case describes how to test the MIPI interface function on the development board.

The backlight control device node on the development board is "/sys/class/backlight/backlight". Execute the following command to change the screen brightness according to the value.

echo 200 | sudo tee /sys/class/backlight/backlight/brightness

This example controls the brightness of the backlight control device node by writing different brightness values ​​to it.

Hardware Hookup

Before testing, please make sure that the interface connection between the MIPI display and the development board is correct. The connection diagram is as follows.

Operation process

Copy the executable program smdt_lcd_demo in the bin directory of this case (05-Development Materials\Software Development Materials\linux_demo\smdt_lcd_demo\bin) to the development board file system (the source code can be viewed in the src path). Open the terminal and execute the following command to switch to the directory where the smdt_lcd_demo executable program is located.

cd ‘the file's directory’

After switching, you can run the command "ls" to check whether the smdt_lcd_demo executable program is in the current directory.

ls

If the executable file smdt_lcd_demo exists in the current directory, continue to perform the following operations: Enter the following command to modify the file permissions.

chmod 777 smdt_lcd_demo

After modifying the permissions, you can enter the following command to check whether the modification is successful.

ls -ld smdt_lcd_demo

The execution result is: -rwxrwxrwx 1 root root 19016 Mar 3 09:55 smdt_lcd_demo.

-rwxrwxrwx means the permissions have been modified successfully, the file can be executed, and you can continue with the following operations.

Continue to enter instructions and view program parameter information.

./lcd_demo -h
./lcd_demo -d /sys/class/backlight/backlight/

The MIPI screen backlight brightness changes from high to low in a cycle, and each level of brightness is maintained for 0.5s. The command window prints the following information:

Press Ctrl+C to exit the test.

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