0458acd998
Co-authored-by: Kevin Schlosser <kdschlosser@users.noreply.github.com> Co-authored-by: Liam <30486941+liamHowatt@users.noreply.github.com>
76 lines
3.4 KiB
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76 lines
3.4 KiB
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============================
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ST7796 LCD Controller driver
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============================
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Overview
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--------
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The `ST7796S <https://www.buydisplay.com/download/ic/ST7796S.pdf>`__ is a single-chip controller/driver for 262K-color, graphic type TFT-LCD. It consists of 960
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source lines and 480 gate lines driving circuits. The ST7796S is capable of connecting directly to an external
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microprocessor, and accepts 8-bit/9-bit/16-bit/18-bit parallel interface, SPI, and the ST7796S also provides
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MIPI interface. Display data can be stored in the on-chip display data RAM of 320x480x18 bits. It can perform
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display data RAM read-/write-operation with no external clock to minimize power consumption. In addition,
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because of the integrated power supply circuit necessary to drive liquid crystal; it is possible to make a display
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system with fewest components.
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The ST7796 LCD controller `driver <https://github.com/lvgl/lvgl/src/drivers/display/st7796>`__ is a platform-agnostic driver, based on the `generic MIPI driver <https://github.com/lvgl/lvgl/doc/integration/drivers/display/gen_mipi.rst>`__.
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It implements display initialization, supports display rotation and implements the display flush callback. The user needs to implement only two platform-specific functions to send
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a command or pixel data to the controller via SPI or parallel bus. Typically these are implemented by calling the appropriate SDK library functions on the given platform.
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Prerequisites
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-------------
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There are no prerequisites.
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Configuring the driver
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----------------------
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Enable the ST7796 driver support in lv_conf.h, by cmake compiler define or by KConfig
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.. code-block:: c
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#define LV_USE_ST7796 1
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Usage
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-----
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You need to implement two platform-dependent functions:
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.. code-block:: c
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/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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int32_t my_lcd_send_cmd(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, const uint8_t *param, size_t param_size)
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{
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...
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}
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/* Send large array of pixel data to the LCD. If necessary, this function has to do the byte-swapping. This function can do the transfer in the background. */
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int32_t my_lcd_send_color(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, uint8_t *param, size_t param_size)
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{
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...
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}
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To create an ST7796-based display use the function
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.. code-block:: c
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/**
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* Create an LCD display with ST7796 driver
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* @param hor_res horizontal resolution
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* @param ver_res vertical resolution
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* @param flags default configuration settings (mirror, RGB ordering, etc.)
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* @param send_cmd platform-dependent function to send a command to the LCD controller (usually uses polling transfer)
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* @param send_color platform-dependent function to send pixel data to the LCD controller (usually uses DMA transfer: must implement a 'ready' callback)
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* @return pointer to the created display
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*/
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lv_display_t * lv_st7796_create(uint32_t hor_res, uint32_t ver_res, lv_lcd_flag_t flags,
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lv_st7796_send_cmd_cb_t send_cmd_cb, lv_st7796_send_color_cb_t send_color_cb);
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For additional details and a working example see the `generic MIPI driver documentation <https://github.com/lvgl/lvgl/doc/integration/drivers/display/gen_mipi.rst>`__.
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.. note::
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You can find a step-by-step guide and the actual implementation of the callbacks on an STM32F746 using STM32CubeIDE and the ST HAL libraries here: :ref:`lcd_stm32_guide`
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