1. Hardware design

The screen I chose here is the 6-inch screen recommended by the Sakura cat boss (that is, the cat screen),Referring to the adapter board drawn by the big guy and the backlight base plate of the training camp,I drew a screen adapter plate with onboard backlight,And a basic screen adapter board (I finally used this board)

Backlight driver circuitry

One is the method provided by the big guy,That is, modify the device tree,Modify the original PWM output level from(20-255)to(20-51),This limits the current,The specific modification method can be seen in the open source project of the cherry cat boss:6Inch cat screen.

The second is to add an on-board backlight on the screen adapter board, because the Taishan faction MIPI interface does not lead to a PWM signal, so there is no way to directly use the backlight PWM signal of the Taishan faction, you need to use GP7101 an I2C to PWM chip to achieve PWM adjustment, the GP7101 is mounted on the I2C bus of the touch screen, and the LED driver chip is controlled by programming the driver and controlling the backlight output PWM signal SY7201ABC Output LED backlight I2C_DSI_ VCC_LED+ and I2C_DSI_VCC_LED-, for more details, please check out Taishan Pi Training Camp - Mobile Integrated Program

In addition, the screen adapter board is also designed with a backlight selection circuit, which can be selected according to the specific solution.

2. Software design

If you choose the onboard backlight,You need to modify the backlight driver and write GP7101,The detailed method is still check out the Taishan faction training camp-mobile phone comprehensive project,I'm sure it's not as good as Wu Gong.Hehe.

3. Shell part

Since my upper shell just digs out the display area, the edge of the upper shell is somewhat high from the screen, which makes it not very friendly to the edge touch of the screen, so if you need to use my shell, you need to consider opening the top slot part larger.

Let's take a look at the final result:

The shell is not very well drawn, forgive me!

For a more detailed demonstration video, you can see the video of Bilibili:https://www.bilibili.com/video/BV1ji421X78k

There is also a 3D printed dragon from JLC, and the effect is still very good.