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rgb_lcd: support restart dma transmission manually

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When doing Flash operations (e.g. OTA), LCD's DMA bandwidth will be not
sufficient, causing the desync between the LCD controller and DMA.

Added a restart function to help the user to make them sync again.
This commit is contained in:
morris
2022-09-22 17:52:52 +08:00
parent 7f5ecbe533
commit 7d39d1223b
5 changed files with 92 additions and 22 deletions
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docs/en/api-reference/peripherals/lcd.rst
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@@ -218,7 +218,7 @@ After we get the LCD handle, the remaining LCD operations are the same for diffe
.. note::
It should never happen in a well-designed embedded application, but it can in theory be possible that the DMA cannot deliver data as fast as the LCD consumes it. In the {IDF_TARGET_NAME} hardware, this leads to the LCD simply outputting dummy bytes while DMA waits for data. If we were to run DMA in a stream fashion, this would mean a de-sync between the LCD address the DMA reads the data for and the LCD address the LCD peripheral thinks it outputs data for, leading to a **permanently** shifted image.
In order to stop this from happening, you can enable the :ref:`CONFIG_LCD_RGB_RESTART_IN_VSYNC` option, so the driver will restart the DMA in the VBlank interrupt; this way we always know where it starts.
In order to stop this from happening, you can either enable the :ref:`CONFIG_LCD_RGB_RESTART_IN_VSYNC` option, so the driver can restart the DMA in the VBlank interrupt automatically or call :cpp:func:`esp_lcd_rgb_panel_restart` to restart the DMA manually. Note :cpp:func:`esp_lcd_rgb_panel_restart` doesn't restart the DMA immediately, the DMA will still be restarted in the next VSYNC event.
Application Example
-------------------