GUIDRV_Lin update callback?

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    • GUIDRV_Lin update callback?

      Hello,

      I am using emWin to control a small 1 bit OLED (SSD1306) display. I am using the GUIDRV_Lin driver as it is the only one provided in the STemWin package that supports 1 bit/pixel.
      The implementation is rather simple - the LCD driver only supports the init command and GUIDRV_Lin writes directly into the framebuffer. All I have to add is after displaying something (eg write some text), I have to manually copy the contents of the framebuffer to the OLED module via SPI.
      Probably this is not the way GUIDRV_Lin is intended to use, but it is simple and works well enough. Is there a way to automatically call the "copy framebuffer to SPI" routine - eg some callback after a screen update?

      Thanks! Martin

    • Hi,

      No unfortunately there is no such function.

      You could try something like:

      C Source Code

      1. while (1) {
      2. DoneSomething = GUI_Exec();
      3. if (DoneSomething) {
      4. UpdateLCD();
      5. }
      6. }





      The disadvantage is that GUI_Exec() returns also with 1 if emWin has processed other things than drawing like timer or touch input.

      Another solution might be to use the multi buffering API.

      In the function LCD_X_Config() you set the VRAM address like this:

      C Source Code

      1. void LCD_X_Config(void) {
      2. static const U32 _aBufferPTRGUI[] = {
      3. LCD_FRAME_BUFFER0,
      4. LCD_FRAME_BUFFER0,
      5. };
      7. GUI_MULTIBUF_Config(2);
      9. ...
      11. ...
      13. ...
      15. LCD_SetBufferPtrEx(0, (void **)_aBufferPTRGUI);
      17. }
      Display All
      Now emWin "thinks" it has to buffers to be used for multibuffering. and will send the LCD_X_SHOWBUFFER command to the driver callback function. This command will be send as soon as the Window Manager has finished drawing all invalid windows.

      In the function LCD_X_DisplayDriver() you can react on the LCD_X_SHOWBUFFER command and send the data to your lcd:


      C Source Code

      1. case LCD_X_SHOWBUFFER: {
      2. SendData();
      3. break;
      4. }

      If you are not using the Window Manager just surround your drawing operations with GUI_MULTIBUF_Begin() and GUI_MULTIBUF_End(). Like:

      C Source Code

      1. GUI_MULTIBUF_Begin();
      2. YourDrawingOperationA();
      3. YourDrawingOperationB();
      4. YourDrawingOperationC();
      5. YourDrawingOperationD();
      6. GUI_MULTIBUF_End();

      When calling GUI_MULTIBUF_Begin() emWin will perform a copy buffer from the front to the backbuffer. Since you have only one buffer (emWin is just thinking you have two) you might want to set a dummy function for copy buffer. Just to avoid any troubles.

      In LCD_X_Config() add:

      C Source Code

      1. LCD_SetDevFunc(0, LCD_DEVFUNC_COPYBUFFER, DummyCPYBuffer);
      The function does actually nothing:


      C Source Code

      1. static void DummyCPYBuffer(int LayerIndex, int IndexSrc, int IndexDst) {
      2. GUI_USE_PARA(LayerIndex);
      3. GUI_USE_PARA(IndexSrc);
      4. GUI_USE_PARA(IndexDst);
      5. }


      Haven't had the chance to check this on a device like your but it seemed to be working on a STM32F746 Disco.

      Regards,
      Sven
      Please read the forum rules before posting.

      Keep in mind, this is *not* a support forum.
      Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
      Should you be entitled to support you can contact us via our support system: segger.com/ticket/
      Or you can contact us via e-mail.

    • Hi,

      my colleague told me that we actually have such a function. I wasn't aware of that.

      Simply call the following function in LCD_X_Config():

      C Source Code

      1. GUI_SetControlHook(UpdateLCD);

      The UpdateLCD() function looks like:

      C Source Code

      1. void UpdateLCD(int LayerIndex, int Cmd) {
      2. GUI_USE_PARA(LayerIndex);
      3. if (Cmd == LCD_CC_UNLOCK) {
      4. SendData();
      5. }
      6. }
      The LCD_CC_LOCK command is send after the Window Manager has drawn the last invalid window.

      It is important that you do NOT use any multibuffering API when using GUI_SetControlHook(). So remove any calls of WM_MULTIBUF_Enable(), GUI_MULTIBUF_Begin()/GUI_MULTIBUF_End() and GUI_MULTIBUF_Config().


      Regards,

      Sven
      Please read the forum rules before posting.

      Keep in mind, this is *not* a support forum.
      Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
      Should you be entitled to support you can contact us via our support system: segger.com/ticket/
      Or you can contact us via e-mail.