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issues reading stm32f4 lcd

Cristian CLC

Hi everyone, i'm working with the stm32f4 lcd module and i realized that whenenever i try to read the screen (actually the ram memory) some data are repeated. For example, after read and write the memory i dont have the same picture despite having done any kind of processing. This is solve just adding a delay function between each reading.
I've tryed working with dma and I am having the same issue.

I would really preciated any help.
Best regards

Parents
  • 0 in reply to Westonsupermare Pier

    I attach the following explanations for a better understanding:

    1) We are trying to process video (in near real time) frames obtained from the Video Display memory (STM32F4DIS-LCD) previously captured from an ov9655 camera.
    2) We are working with the OV9655 project example (under keil uvision) as base project.
    3) We wish to transfer each frame video from Video Display Memory to Discovery SRAM, via DMA, to obtain a faster performance.
    4) As we are limited for the Discovery SRAM size (only 192KB), we only could transfer part of each frame to processing.
    5) Everytime we read the Video Display Memory we are getting a pixel data repeated each several pixels (it seems to be in a random way).
    6) This kind of behaviour is happening both via DMA and via the LCD_ReadRAM() function, but if we add a delay function (1 ms aprox) following the LCD_ReadRAM() function the reading is ok.

    Best regards.

Reply
  • 0 in reply to Westonsupermare Pier

    I attach the following explanations for a better understanding:

    1) We are trying to process video (in near real time) frames obtained from the Video Display memory (STM32F4DIS-LCD) previously captured from an ov9655 camera.
    2) We are working with the OV9655 project example (under keil uvision) as base project.
    3) We wish to transfer each frame video from Video Display Memory to Discovery SRAM, via DMA, to obtain a faster performance.
    4) As we are limited for the Discovery SRAM size (only 192KB), we only could transfer part of each frame to processing.
    5) Everytime we read the Video Display Memory we are getting a pixel data repeated each several pixels (it seems to be in a random way).
    6) This kind of behaviour is happening both via DMA and via the LCD_ReadRAM() function, but if we add a delay function (1 ms aprox) following the LCD_ReadRAM() function the reading is ok.

    Best regards.

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