MIPI DSI not working on STM32U5

[Charlie CHEN]

Hi,

I have an issue on MIPI Display with our custom board, information as below, 

• Core: STM32U599NJH6
• Frame Buffer Address: 0x200D0000 (Internal SRAM)
• MIPI Driver : ST7797
• Resolution: 400*400

Reference example : STM32Cube_FW_U5_V1.6.0\ STM32U5x9J-DK\ DSI_VideoMode_SingleBuffer

I have noticed  that example code is the same MIPI command and also LTDC timing as mine.

And I set as the same ,but still not display anything. So I checked few things,

1.  DSI_Dn/Dp signal in scope are the same polarity (It should be differential signal)
   > PCB layout & Schematic both design in correct. And Dn/Dp is in correct impedance.
   > There is a saying, no display or Black  will show the same polarity, is it correct?
   
   
2. In example code, there are two different CMD(SetPanelConfig, mipi_config).
   > After set with mipi_config, there is no change on display and same polarity.
   > After set with SetPanelConfig, display appear stripe but same polarity.

 

If it is correct of my understanding, LP mode is for CMD configuration on level ~1.2V, HS mode is in data transfer for display on level ~200mV.

But as my measure, either same polarity or always on level 1.2V.

 

Is there anything I missed?

Any help will be appreciate~

 

Thanks.

 

 

[Charlie CHEN]

Hi, 

Is there anyone can help?

 

Thanks.

[debugging]

Since you did not mention the panel model hard to guess. Some LCD's need specific I2C commands to get them working and it's often not documented. Perhaps contact the supplier/manufacturer ?