How to understand if frame buffer has changed with TouchGFX lib

[Danix2k]

Hi,

I have integrated with lwIP and freeRTOS a VNC server on a STM32H757-EVAL.

A VNC client works fine and I can see on it the first frame buffer drawn by the application; according to the VNC standard, the server should send a "new tile" (a square of pixel) to re-draw the frame buffer changed (if something happens and change it - i.e. slider, button clicked, etc..).

Is there any function or method to understand which pixel (or pixelS) has changed (in term of X and Y coordinates) from the previous frame buffer?

In this way, I can recreate a new tile and send it to the VNC client without re-send every time the whole frame buffer using less bandwidth.

Thanks for your help.

Regards.

[MM..1]

In partial framebuffer mode you can simple handle this in handle rectangle target implementation.

For full single or double you can too use target parts of code ...

[ktrofimo]

What VNC server do you use?​

[Danix2k]

Hi,

in my case I'm using full single buffer for my display.

Do you think that the API for partial frame buffer continue to work even if I set it as REFRESH_STRATEGY_DEFAULT? Because I use a LTDC-DSI display in video mode and I don't need to re-write touchgfxDisplayDriverTransmitActive or touchgfxDisplayDriverTransmitBlock.

[Danix2k]

I use VNC server from ecos operating System; on the internet you can find VNC server source code and adapt it to FreeRTOS and LWIP.

[ktrofimo]

I am doing actually the same thing (also ecos). Not using any of their drawing ot text functions (thanks to TouchGFX)​, but you just step ahead of me 🙂 I was thinking to extend Invalidate() function because it should contain coordinates of area was drawn, but I not realized this idea yet.

[Danix2k]

Now I'm trying to understand if I can use API for partial frame buffer strategy (as suggest by @MM..1​ . After that I can check Invalidate function. Let me know if you can try it before I do.

[MM..1 · Accepted solution]

Try breakpoint and check rect

/**
 * This function is called whenever the framework has performed a partial draw.
 *
 * @param rect The area of the screen that has been drawn, expressed in absolute coordinates.
 *
 * @see flushFrameBuffer().
 */
void TouchGFXHAL::flushFrameBuffer(const touchgfx::Rect& rect)
{
    // Calling parent implementation of flushFrameBuffer(const touchgfx::Rect& rect).
    //
    // To overwrite the generated implementation, omit call to parent function
    // and implemented needed functionality here.
    // Please note, HAL::flushFrameBuffer(const touchgfx::Rect& rect) must
    // be called to notify the touchgfx framework that flush has been performed.
 
    TouchGFXGeneratedHAL::flushFrameBuffer(rect);
}
 

[Danix2k]

Hi @MM..1​ ,

I was exactly trying this and it works.

I report below the modified code.

void TouchGFXHAL::flushFrameBuffer(const touchgfx::Rect& rect)
{
    // Calling parent implementation of flushFrameBuffer(const touchgfx::Rect& rect).
    //
    // To overwrite the generated implementation, omit call to parent function
    // and implemented needed functionality here.
    // Please note, HAL::flushFrameBuffer(const touchgfx::Rect& rect) must
    // be called to notify the touchgfx framework that flush has been performed.
 
    /* USER CODE BEGIN flushFrameBuffer step 1 */
    TouchGFXGeneratedHAL::flushFrameBuffer(rect);
    extern volatile int tile_updated[NUM_TILES_Y_AXIS][NUM_TILES_X_AXIS];
    extern SemaphoreHandle_t    s_xMutexClientLock;
    extern SemaphoreHandle_t    s_xSemphClientWait;
    extern volatile int update_req;
    
    uint16_t i,j;
    printf("RECT: x=%d, y=%d, width=%d, height=%d\r\n", 
	   rect.x, rect.y, rect.width, rect.height);
    if(s_xSemphClientWait != NULL && s_xMutexClientLock != NULL)
    {
      /* Non-incremental mode - mark the squares that need to be updated */
      for (i = (rect.x)/TILE_SIZE;
	   i <= (rect.x + rect.width)/TILE_SIZE;
	   i++)
      {
	for (j = (rect.y)/TILE_SIZE;
	     j <= (rect.y + rect.height)/TILE_SIZE;
	     j++)
	{
	  tile_updated[j][i] = 1;
	}
      }
      xSemaphoreTake(s_xMutexClientLock, portMAX_DELAY);
      update_req = 1;
      printf("signal da flushFrameBuffer\r\n");
      xSemaphoreGive(s_xMutexClientLock);
      xSemaphoreGive(s_xSemphClientWait);
    }
    /* USER CODE END flushFrameBuffer step 1 */
}

[JureL]

Hi @Danix2k​ and @ktrofimo​,

did you managed to sucessfuly port ecos VNC to freertos+lwip+touchgfx ? Are you willing to share project or source code for it ?

Best regards