Generating DSI code without camera interface

[mvonahnen]

Posted on April 11, 2017 at 18:26

I want to generate test patterns to a display. Is there any examples of driving the DSI output with internal memory?

[Imen.D]

Posted on April 11, 2017 at 19:08

Hello

Von_Ahnen.Michael

,

What do you mean 'without camera interface' ? Could you please provide more details about your generate 'test patterns to a display' and which device are you using ?

You'll probably want to reviewLCD_DSI examples within STM32CubeF4/F7 firmware package that will help you to have more idea on how implementation is done.

So, you can refer to the working example in the STM32Cube package relevant for your device :

• STM32Cube_FW_F7_V1.6.0\Projects\STM32F769I_EVAL\Examples\LCD_DSI

• STM32Cube_FW_F4_V1.0\Projects\STM32469I_EVAL\Examples\LCD_DSI

May this application note helps you:

• http://www.st.com/content/ccc/resource/technical/document/application_note/group0/1d/b8/33/4f/dc/0a/45/52/DM00287601/files/DM002876pdf/jcr:content/translations/en.DM002876pdf

  DSI Host on STM32F4 Series and STM32F7 Series microcontrollers

• http://www.st.com/content/ccc/resource/technical/document/application_note/group0/25/ca/f9/b4/ae/fc/4e/1e/DM00287603/files/DM002876pdf/jcr:content/translations/en.DM002876pdf

  : LCD-TFT display controller (LTDC) on STM32 MCUs

• http://www.st.com/content/ccc/resource/training/technical/product_training/group0/3f/7b/af/97/88/ba/48/33/STM32F7_Peripheral_LTDC/files/STM32F7_Peripheral_LTDC.pdf/jcr:content/translations/en.STM32F7_Peripheral_LTDC.pdf

https://community.st.com/message/146432-an4860-and-an4861-new-application-notes-for-graphic-usecases

I hope that this brings some help to you.

Imen

[mvonahnen]

Posted on April 11, 2017 at 19:22

So let me make sure I understand this:

The DSIHOST supports 720P30 (on the STM32F769 per the datasheet)

To enable the DSIHOST in STM32CubeMX, I must also enable the LTDC

The LTDC does not support 720P30 (from trying to match the parameters on STM32CubeMX).

So any display I want to generate, I need code that does not use the LTDC?

[mvonahnen]

Posted on April 11, 2017 at 20:00

All of the examples are resolutions lower than 720P30.  Does that indicate that this resolution is not really possible?

[Imen.D]

Posted on April 13, 2017 at 12:31

Hi

Von_Ahnen.Michael

,

Please note that you can interface STM32 to your display either with:

• DSI serial interface (using LTDC+DSI Host): DSI Host will serialize the parallel stream of data from the LTDC
• or with parallel RGB interface (using LTDC).

Regarding LTDC configuration, you should use STM32CubeMX Version 4.1.

In this new version there is no more limitation on LTDC parameters that prevents from using 720p

But in order to know if your display can be supported, you must consider the pixel clock parameter of your display.

In fact, for the STM32 DSI Host there are two constraints that limit the maximum supported pixel clock which are:

• the DSI link maximum bandwidth:

  • The maximum link bandwidth is 1Gb/s (2 lanes mode)
  • The equivalent maximum pixel clock supported is 5Mhz (16bpp) or 5Mhz (24bpp)
  • More details in

    /external-link.jspa?url=http%3A%2F%2Fwww.st.com%2Fcontent%2Fccc%2Fresource%2Ftechnical%2Fdocument%2Fapplication_note%2Fgroup0%2F1d%2Fb8%2F33%2F4f%2Fdc%2F0a%2F45%2F52%2FDM00287601%2Ffiles%2FDM002876pdf%2Fjcr%3Acontent%2Ftranslations%2Fen.DM002876pdf

    DSI Host on STM32F4 Series and STM32F7 Series microcontrollers

• System constraints:

  • This is related to system constraints that may limit the speed of LTDC fetching the data without risking to have Fifo under run on LTDC side.

  • /external-link.jspa?url=http%3A%2F%2Fwww.st.com%2Fcontent%2Fccc%2Fresource%2Ftechnical%2Fdocument%2Fapplication_note%2Fgroup0%2F25%2Fca%2Ff9%2Fb4%2Fae%2Ffc%2F4e%2F1e%2FDM00287603%2Ffiles%2FDM002876pdf%2Fjcr%3Acontent%2Ftranslations%2Fen.DM002876pdf

    gives some figures of the max pixel clock supported in different scenarios.

If you use LTDC parallel RGB interface, only the second constraint is to be considered.

Hope this bring you some help.

Thanks

Imen

[mvonahnen]

Posted on May 03, 2017 at 17:09

I guess I am confused about your response.  I am trying to use the pattern generator on the MIPI DSI interface and you are referencing app notes about the parallel interface.  None of the HAL code examples use the test patterns and I had thought it was trivial to enable, but it is not working on my board.  I don't see any transitions on the data pins.

[mvonahnen]

Posted on May 04, 2017 at 20:30

So from what I can tell from this post and others I searched, there does not appear to be any experience in using the DSI interface to configure the panels nor is there any example code for using the internal pattern generator for the DSI interface.  Is this true?

[Tesla DeLorean]

Posted on May 04, 2017 at 22:46

>>

Is this true?

Forums can be like empty rooms, there's no guarantee that anyone with the experience you want is in the room, or that they are free to talk to you. The engineers that designed/implement the stuff are firewalled behind FAEs. Don't ask rhetorical questions. When you're first up the mountain, you have to run your own rope line. In your situation, I'd RTFM, and Experiment..

[mvonahnen]

Posted on May 04, 2017 at 22:55

So it is not fair to ask if anybody has experience with the issue I am working through?  It was not intended as a rhetorical question.  And yes, I am not just waiting around twiddling my thumbs, I am reading the manual and running my board trying to work through things.  Given this is the only source of information for smaller customers, I would hope that instead of just jumping in with quick snappy responses that the people responding would try to be helpful.  It is frustrating that forum's like this seem to dominated by people who like to put people in their place instead of helping them.