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 ...

[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.

[ktrofimo]

What VNC server do you use?​

[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.

[MM..1]

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

[ktrofimo]

Sorry for the late reply...

Code is still too dirty and full of hacks and I am not ready to publish it. Basically it is the same ECOS VNC server code where OS functions ported to the corresponding CMSISv2 functions.

[JureL]

Thank you for reply. Is this the source code you started from :

https://github.com/kaos/ecos/tree/master/packages/net/vnc_server/current

?

Regards, Jure