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Danix2k
Danix2k
Associate III
June 29, 2022
Solved

How to understand if frame buffer has changed with TouchGFX lib

  • June 29, 2022
  • 15 replies
  • 4902 views

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.

This topic has been closed for replies.
Best answer by 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);
}
 

15 replies

MM..1
MM..1
Super User
June 29, 2022

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
Danix2kAuthor
Associate III
June 30, 2022

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
ktrofimo
Senior III
June 30, 2022

What VNC server do you use?​

Danix2k
Danix2kAuthor
Associate III
June 30, 2022

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
ktrofimo
Senior III
June 30, 2022

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
MM..1Best answer
Super User
June 30, 2022

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
Danix2kAuthor
Associate III
June 30, 2022

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
JureL
Associate III
August 31, 2022

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
ktrofimo
Senior III
September 19, 2022

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
JureL
Associate III
September 19, 2022

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

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