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========================
Linux Framebuffer Driver
========================
Overview
--------
The Linux framebuffer (fbdev) is a linux subsystem used to display graphics. It is a hardware-independent API that gives user space software
access to the framebuffer (the part of a computer's video memory containing a current video frame) using only the Linux kernel's own basic
facilities and its device file system interface, avoiding the need for libraries that implement video drivers in user space.
Prerequisites
-------------
Your system has a framebuffer device configured (usually under ``/dev/fb0``).
Configuring the driver
----------------------
Enable the framebuffer driver support in lv_conf.h, by cmake compiler define or by KConfig. Additionally you may configure the rendering
mode.
.. code-block:: c
#define LV_USE_LINUX_FBDEV 1
#define LV_LINUX_FBDEV_RENDER_MODE LV_DISPLAY_RENDER_MODE_PARTIAL
Usage
-----
To set up a framebuffer-based display, first create a display with ``lv_linux_fbdev_create``. Afterwards set the framebuffer device
node on the display (usually this is ``/dev/fb0``).
.. code-block:: c
lv_display_t *disp = lv_linux_fbdev_create();
lv_linux_fbdev_set_file(disp, "/dev/fb0");
If your screen stays black or only draws partially, you can try enabling direct rendering via ``LV_DISPLAY_RENDER_MODE_DIRECT``. Additionally,
you can activate a force refresh mode with ``lv_linux_fbdev_set_force_refresh(true)``. This usually has a performance impact though and shouldn't
be enabled unless really needed.

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=================================================
Generic MIPI DCS compatible LCD Controller driver
=================================================
Overview
--------
From the `Wikipedia <https://en.wikipedia.org/wiki/MIPI_Alliance>`__:
`MIPI Alliance <https://www.mipi.org/>`__ is a global business alliance that develops technical specifications
for the mobile ecosystem, particularly smart phones but including mobile-influenced industries. MIPI was founded in 2003 by Arm, Intel, Nokia, Samsung,
STMicroelectronics and Texas Instruments.
MIPI Alliance published a series of specifications related to display devices, including DBI (Display Bus Interface), DSI (Display Serial Interface) and DCS
(Display Command Set). Usually when one talks about a MIPI-compatible display, one thinks of a device with a DSI serial interface. However, the Display Bus Interface specification
includes a number of other, legacy interfaces, like SPI serial, or i8080-compatible parallel interface, which are often used to interface LCD displays to lower-end microcontrollers.
Furthermore, the DCS specification contains a standard command set, which is supported by a large number of legacy TFT LCD controllers, including the popular Sitronix
(ST7735, ST7789, ST7796) and Ilitek (ILI9341) SOCs. These commands provide a common interface to configure display orientation, color resolution, various power modes, and provide generic video memory access. On top
of that standard command set each LCD controller chip has a number of vendor-specific commands to configure voltage generator levels, timings, or gamma curves.
.. note::
It is important to understand that this generic MIPI LCD driver is not a hardware driver for displays with the DSI ("MIPI") serial interface. Instead, it implements the MIPI DCS command set used in many LCD controllers with an SPI or i8080 bus, and provides a common framework for chip-specific display controllers.
.. tip::
Although this is a generic driver, it can be used to support compatible chips which do not have a specific driver.
Prerequisites
-------------
There are no prerequisites.
Configuring the driver
----------------------
Enable the generic MIPI LCD driver support in lv_conf.h, by cmake compiler define or by KConfig
.. code-block:: c
#define LV_USE_GENERIC_MIPI 1
.. note::
:c:macro:`LV_USE_GENERIC_MIPI` is automatically enabled when a compatible driver is enabled.
Usage
-----
You need to implement two platform-dependent functions:
.. code-block:: c
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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)
{
...
}
/* 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. */
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)
{
...
}
The only difference between the :cpp:func:`my_lcd_send_cmd()` and :cpp:func:`my_lcd_send_color()` functions is that :cpp:func:`my_lcd_send_cmd()` is used to send short commands and it is expected
complete the transaction when it returns (in other words, it should be blocking), while :cpp:func:`my_lcd_send_color()` is only used to send pixel data, and it is recommended to use
DMA to transmit data in the background. More sophisticated methods can be also implemented, like queuing transfers and scheduling them in the background.
Please note that while display flushing is handled by the driver, it is the user's responsibility to call :cpp:func:`lv_display_flush_ready()`
when the color transfer completes. In case of a DMA transfer this is usually done in a transfer ready callback.
.. note::
While it is acceptable to use a blocking implementation for the pixel transfer as well, performance will suffer.
.. tip::
Care must be taken to avoid sending a command while there is an active transfer going on in the background. It is the user's responsibility to implement this either
by polling the hardware, polling a global variable (which is reset at the end of the transfer), or by using a semaphore or other locking mechanism.
Please also note that the driver does not handle the draw buffer allocation, because this may be platform-dependent, too. Thus you need to allocate the buffers and assign them
to the display object as usual by calling :cpp:func:`lv_display_set_buffers()`.
The driver can be used to create multiple displays. In such a configuration the callbacks must be able to distinguish between the displays. Usually one would
implement a separate set of callbacks for each display. Also note that the user must take care of arbitrating the bus when multiple devices are connected to it.
Example
-------
.. note::
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`
.. code-block:: c
#include "src/drivers/display/st7789/lv_st7789.h"
#define LCD_H_RES 240
#define LCD_V_RES 320
#define LCD_BUF_LINES 60
lv_display_t *my_disp;
...
/* Initialize LCD I/O bus, reset LCD */
static int32_t my_lcd_io_init(void)
{
...
return HAL_OK;
}
/* Send command to the LCD controller */
static void my_lcd_send_cmd(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, const uint8_t *param, size_t param_size)
{
...
}
/* Send pixel data to the LCD controller */
static void my_lcd_send_color(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, uint8_t *param, size_t param_size)
{
...
}
int main(int argc, char ** argv)
{
...
/* Initialize LVGL */
lv_init();
/* Initialize LCD bus I/O */
if (my_lcd_io_init() != 0)
return;
/* Create the LVGL display object and the LCD display driver */
my_disp = lv_lcd_generic_mipi_create(LCD_H_RES, LCD_V_RES, LV_LCD_FLAG_NONE, my_lcd_send_cmd, my_lcd_send_color);
/* Set display orientation to landscape */
lv_display_set_rotation(my_disp, LV_DISPLAY_ROTATION_90);
/* Configure draw buffers, etc. */
uint8_t * buf1 = NULL;
uint8_t * buf2 = NULL;
uint32_t buf_size = LCD_H_RES * LCD_BUF_LINES * lv_color_format_get_size(lv_display_get_color_format(my_disp));
buf1 = lv_malloc(buf_size);
if(buf1 == NULL) {
LV_LOG_ERROR("display draw buffer malloc failed");
return;
}
/* Allocate secondary buffer if needed */
...
lv_display_set_buffers(my_disp, buf1, buf2, buf_size, LV_DISPLAY_RENDER_MODE_PARTIAL);
ui_init(my_disp);
while(true) {
...
/* Periodically call the lv_timer handler */
lv_timer_handler();
}
}
Advanced topics
---------------
Create flags
^^^^^^^^^^^^
The third argument of the :cpp:func:`lv_lcd_generic_mipi_create()` function is a flag array. This can be used to configure the orientation and RGB ordering of the panel if the
default settings do not work for you. In particular, the generic MIPI driver accepts the following flags:
.. code-block:: c
LV_LCD_FLAG_NONE
LV_LCD_FLAG_MIRROR_X
LV_LCD_FLAG_MIRROR_Y
LV_LCD_FLAG_BGR
You can pass multiple flags by ORing them together, e.g., :c:macro:`LV_LCD_FLAG_MIRROR_X` ``|`` :c:macro:`LV_LCD_FLAG_BGR`.
Custom command lists
^^^^^^^^^^^^^^^^^^^^
While the chip-specific drivers do their best to initialize the LCD controller correctly, it is possible, that different TFT panels need different configurations.
In particular a correct gamma setup is crucial for good color reproduction. Unfortunately, finding a good set of parameters is not easy. Usually the manufacturer
of the panel provides some example code with recommended register settings.
You can use the ``my_lcd_send_cmd()`` function to send an arbitrary command to the LCD controller. However, to make it easier to send a large number of parameters
the generic MIPI driver supports sending a custom command list to the controller. The commands must be put into a 'uint8_t' array:
.. code-block:: c
static const uint8_t init_cmd_list[] = {
<command 1>, <number of parameters>, <parameter 1>, ... <parameter N>,
<command 2>, <number of parameters>, <parameter 1>, ... <parameter N>,
...
LV_LCD_CMD_DELAY_MS, LV_LCD_CMD_EOF /* terminate list: this is required! */
};
...
lv_lcd_generic_mipi_send_cmd_list(my_disp, init_cmd_list);
You can add a delay between the commands by using the pseudo-command ``LV_LCD_CMD_DELAY_MS``, which must be followed by the delay given in 10ms units.
To terminate the command list you must use a delay with a value of ``LV_LCD_CMD_EOF``, as shown above.
See an actual example of sending a command list `here <https://github.com/lvgl/lvgl/src/drivers/display/st7789/lv_st7789.c>`__.

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=============================
ILI9341 LCD Controller driver
=============================
Overview
--------
The `ILI9341 <https://www.buydisplay.com/download/ic/ILI9341.pdf>`__ is a 262,144-color single-chip SOC driver for a-TFT liquid crystal display with resolution of 240RGBx320
dots, comprising a 720-channel source driver, a 320-channel gate driver, 172,800 bytes GRAM for graphic
display data of 240RGBx320 dots, and power supply circuit.
ILI9341 supports parallel 8-/9-/16-/18-bit data bus MCU interface, 6-/16-/18-bit data bus RGB interface and
3-/4-line serial peripheral interface (SPI).
The ILI9341 LCD controller `driver <https://github.com/lvgl/lvgl/src/drivers/display/ili9341>`__ is a platform-agnostic driver, based on the `generic MIPI driver <https://github.com/lvgl/lvgl/doc/integration/drivers/display/gen_mipi.rst>`__.
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
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.
Prerequisites
-------------
There are no prerequisites.
Configuring the driver
----------------------
Enable the ILI9341 driver support in lv_conf.h, by cmake compiler define or by KConfig
.. code-block:: c
#define LV_USE_ILI9341 1
Usage
-----
You need to implement two platform-dependent functions:
.. code-block:: c
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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)
{
...
}
/* 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. */
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)
{
...
}
To create an ILI9341-based display use the function
.. code-block:: c
/**
* Create an LCD display with ILI9341 driver
* @param hor_res horizontal resolution
* @param ver_res vertical resolution
* @param flags default configuration settings (mirror, RGB ordering, etc.)
* @param send_cmd platform-dependent function to send a command to the LCD controller (usually uses polling transfer)
* @param send_color platform-dependent function to send pixel data to the LCD controller (usually uses DMA transfer: must implement a 'ready' callback)
* @return pointer to the created display
*/
lv_display_t * lv_ili9341_create(uint32_t hor_res, uint32_t ver_res, lv_lcd_flag_t flags,
lv_ili9341_send_cmd_cb_t send_cmd_cb, lv_ili9341_send_color_cb_t send_color_cb);
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>`__.
.. note::
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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=======
Display
=======
.. toctree::
:maxdepth: 2
fbdev
gen_mipi
ili9341
lcd_stm32_guide
renesas_glcdc
st_ltdc
st7735
st7789
st7796

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.. _lcd_stm32_guide:
=========================================================================
Step-by-step Guide: How to use the LVGL v9 LCD drivers with STM32 devices
=========================================================================
Introduction
------------
This guide is intended to be a step-by-step instruction of how to configure the STM32Cube HAL with the new TFT-LCD display drivers introduced in LVGL v9.0. The example code has been tested on the STM32F746-based Nucleo-F746ZG board with an ST7789-based LCD panel connected via SPI. The application itself and the hardware configuration code were generated with the STM32CubeIDE 1.14.0 tool.
.. tip::
ST Micro provide their own TFT-LCD drivers in their X-CUBE-DISPLAY Software Extension Package. While these drivers can be used with LVGL as well, the LVGL LCD drivers do not depend on this package.
The LVGL LCD drivers are meant as an alternative, simple to use API to implement LCD support for your LVGL-based project on any platform. Moreover, even in the initial release we support more LCD controllers than X-CUBE-DISPLAY currently provides, and we plan to add support for even more LCD controllers in the future.
Please note however, that – unlike X-CUBE-DISPLAY – the LVGL LCD drivers do not implement the communication part, whether SPI, parallel i8080 bus or other. It is the user's responsibility to implement – and optimize – these on their chosen platform. LVGL will only provide examples for the most popular platforms.
By following the steps you will have a fully functional program, which can be used as the foundation of your own LVGL-based project. If you are in a hurry and not interested in the details, you can find the final project `here <https://github.com/lvgl/lv_port_lcd_stm32>`__. You will only need to configure LVGL to use the driver corresponding to your hardware (if it is other than the ST7789), and implement the function ``ui_init()`` to create your widgets.
.. note::
This example is not meant as the best possible implementation, or the recommended solution. It relies solely on the HAL drivers provided by ST Micro, which favor portability over performance. Despite of this the performance is very good, thanks to the efficient, DMA-based implementation of the drivers.
.. note::
Although the example uses FreeRTOS, this is not a strict requirement with the LVGL LCD display drivers.
You can find the source code snippets of this guide in the `lv_port_lcd_stm32_template.c <https://github.com/lvgl/lvgl/examples/porting/lv_port_lcd_stm32_template.c>`__ example.
Hardware configuration
----------------------
In this example we'll use the SPI1 peripheral to connect the microcontroller to the LCD panel. Besides the hardware-controlled SPI pins SCK and MOSI we need some additional output pins for the chip select, command/data select, and LCD reset:
==== ============= ======= ==========
pin configuration LCD user label
==== ============= ======= ==========
PA4 GPIO_Output CS LCD_CS
PA5 SPI1_SCK SCK --
PA7 SPI1_MOSI SDI --
PA15 GPIO_Output RESET LCD_RESET
PB10 GPIO_Output DC LCD_DCX
==== ============= ======= ==========
Step-by-step instructions
-------------------------
#. Create new project in File/New/STM32 Project.
#. Select target processor/board.
#. Set project name and location.
#. Set Targeted Project Type to STM32Cube and press Finish.
#. Say "Yes" to Initialize peripherals with their default Mode? After the project is created, the configuration file (.ioc) is opened automatically.
#. Switch to the Pinout & Configuration tab.
#. In the System Core category switch to RCC.
#. Set High Speed Clock to "BYPASS Clock Source", and Low Speed Clock to "Crystal/Ceramic Resonator".
#. In the System Core category select SYS, and set Timebase Source to other than SysTick (in our example, TIM2).
#. Switch to the Clock Configuration tab.
#. Set the HCLK clock frequency to the maximum value (216 MHz for the STM32F746).
#. Switch back to the Pinout & Configuration tab, and in the Middleware and Software Packs category select FREERTOS.
#. Select Interface: CMSIS_V1.
#. In the Advanced Settings tab enable USE_NEWLIB_REENTRANT. We are finished here.
#. In the Pinout view configure PA5 as SPI1_SCK, PA7 as SPI1_MOSI (right click the pin and select the function).
#. In the Pinout & Configuration/Connectivity category select SPI1.
#. Set Mode to Transmit Only Master, and Hardware NSS Signal to Disable.
#. In the Configuration subwindow switch to Parameter Settings.
#. Set Frame Format to Motorola, Data Size to 8 Bits, First Bit to MSB First.
#. Set the Prescaler to the maximum value according to the LCD controller’s datasheet (e.g., 15 MBits/s). Set CPOL/CPHA as required (leave as default).
#. Set NSSP Mode to Disabled and NSS Signal Type to Software.
#. In DMA Settings add a new Request for SPI1_TX (when using SPI1).
#. Set Priority to Medium, Data Width to Half Word.
#. In NVIC Settings enable SPI1 global interrupt.
#. In GPIO Settings set SPI1_SCK to Pull-down and Very High output speed and set the User Label to ``LCD_SCK``.
#. Set SPI1_MOSI to Pull-up and Very High, and name it ``LCD_SDI``.
#. Select System Core/GPIO category. In the Pinout view configure additional pins for chip select, reset and command/data select. Name them ``LCD_CS``, ``LCD_RESET`` and ``LCD_DCX``, respectively. Configure them as GPIO Output. (In this example we will use PA4 for ``LCD_CS``, PA15 for ``LCD_RESET`` and PB10 for ``LCD_DCX``.)
#. Set ``LCD_CS`` to No pull-up and no pull-down, Low level and Very High speed.
#. Set ``LCD_RESET`` to Pull-up and High level.
#. Set ``LCD_DCX`` to No pull-up and no pull-down, High level and Very High speed.
#. Open the Project Manager tab, and select Advanced Settings. On the right hand side there is a Register Callback window. Select SPI and set it to ENABLE.
#. We are ready with the hardware configuration. Save the configuration and let STM32Cube generate the source.
#. In the project tree clone the LVGL repository into the Middlewares/Third_Party folder (this tutorial uses the release/v9.0 branch of LVGL):
.. code-block:: dosbatch
git clone https://github.com/lvgl/lvgl.git -b release/v9.0
#. Cloning should create an 'lvgl' subfolder inside the 'Third_Party' folder. From the 'lvgl' folder copy 'lv_conf_template.h' into the 'Middlewares' folder, and rename it to 'lv_conf.h'. Refresh the project tree.
#. Open 'lv_conf.h', and in line 15 change ``#if 0`` to ``#if 1``.
#. Search for the string ``LV_USE_ST7735``, and enable the appropriate LCD driver by setting its value to 1. This example uses the ST7789 driver:
.. code-block:: c
#define LV_USE_ST7789 1
#. Right click the folder 'Middlewares/Third_Party/lvgl/tests', select Resource Configurations/Exclude from Build..., check both Debug and Release, then press OK.
#. Right click the project name and select "Properties". In the C/C++ Build/Settings panel select MCU GCC Compiler/Include paths. In the Configuration dropdown select [ All configurations ]. Add the following Include path:
.. code-block:: c
../Middlewares/Third_Party/lvgl
#. Open Core/Src/stm32xxx_it.c (the file name depends on the processor variation). Add 'lv_tick.h' to the Private includes section:
.. code-block:: c
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "./src/tick/lv_tick.h"
/* USER CODE END Includes */
#. Find the function ``TIM2_IRQHandler``. Add a call to ``lv_tick_inc()``:
.. code-block:: c
void TIM2_IRQHandler(void)
{
/* USER CODE BEGIN TIM2_IRQn 0 */
/* USER CODE END TIM2_IRQn 0 */
HAL_TIM_IRQHandler(&htim2);
/* USER CODE BEGIN TIM2_IRQn 1 */
lv_tick_inc(1);
/* USER CODE END TIM2_IRQn 1 */
}
#. Save the file, then open Core/Src/main.c. Add the following lines to the Private includes (if your LCD uses other than the ST7789, replace the driver path and header with the appropriate one):
.. code-block:: c
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "lvgl.h"
#include "./src/drivers/display/st7789/lv_st7789.h"
/* USER CODE END Includes */
#. Add the following lines to Private defines (change them according to your LCD specs):
.. code-block:: c
#define LCD_H_RES 240
#define LCD_V_RES 320
#define BUS_SPI1_POLL_TIMEOUT 0x1000U
#. Add the following lines to the Private variables:
.. code-block:: c
osThreadId LvglTaskHandle;
lv_display_t *lcd_disp;
volatile int lcd_bus_busy = 0;
#. Add the following line to the Private function prototypes:
.. code-block:: c
void ui_init(lv_display_t *disp);
void LVGL_Task(void const *argument);
#. Add the following lines after USER CODE BEGIN RTOS_THREADS:
.. code-block:: c
osThreadDef(LvglTask, LVGL_Task, osPriorityIdle, 0, 1024);
LvglTaskHandle = osThreadCreate(osThread(LvglTask), NULL);
#. Copy and paste the hardware initialization and the transfer callback functions from the example code after USER CODE BEGIN 4:
.. code-block:: c
/* USER CODE BEGIN 4 */
void lcd_color_transfer_ready_cb(SPI_HandleTypeDef *hspi)
{
/* CS high */
HAL_GPIO_WritePin(LCD_CS_GPIO_Port, LCD_CS_Pin, GPIO_PIN_SET);
lcd_bus_busy = 0;
lv_display_flush_ready(lcd_disp);
}
/* Initialize LCD I/O bus, reset LCD */
static int32_t lcd_io_init(void)
{
/* Register SPI Tx Complete Callback */
HAL_SPI_RegisterCallback(&hspi1, HAL_SPI_TX_COMPLETE_CB_ID, lcd_color_transfer_ready_cb);
/* reset LCD */
HAL_GPIO_WritePin(LCD_RESET_GPIO_Port, LCD_RESET_Pin, GPIO_PIN_RESET);
HAL_Delay(100);
HAL_GPIO_WritePin(LCD_RESET_GPIO_Port, LCD_RESET_Pin, GPIO_PIN_SET);
HAL_Delay(100);
HAL_GPIO_WritePin(LCD_CS_GPIO_Port, LCD_CS_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(LCD_DCX_GPIO_Port, LCD_DCX_Pin, GPIO_PIN_SET);
return HAL_OK;
}
/* Platform-specific implementation of the LCD send command function. In general this should use polling transfer. */
static void lcd_send_cmd(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, const uint8_t *param, size_t param_size)
{
LV_UNUSED(disp);
while (lcd_bus_busy); /* wait until previous transfer is finished */
/* Set the SPI in 8-bit mode */
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
HAL_SPI_Init(&hspi1);
/* DCX low (command) */
HAL_GPIO_WritePin(LCD_DCX_GPIO_Port, LCD_DCX_Pin, GPIO_PIN_RESET);
/* CS low */
HAL_GPIO_WritePin(LCD_CS_GPIO_Port, LCD_CS_Pin, GPIO_PIN_RESET);
/* send command */
if (HAL_SPI_Transmit(&hspi1, cmd, cmd_size, BUS_SPI1_POLL_TIMEOUT) == HAL_OK) {
/* DCX high (data) */
HAL_GPIO_WritePin(LCD_DCX_GPIO_Port, LCD_DCX_Pin, GPIO_PIN_SET);
/* for short data blocks we use polling transfer */
HAL_SPI_Transmit(&hspi1, (uint8_t *)param, (uint16_t)param_size, BUS_SPI1_POLL_TIMEOUT);
/* CS high */
HAL_GPIO_WritePin(LCD_CS_GPIO_Port, LCD_CS_Pin, GPIO_PIN_SET);
}
}
/* Platform-specific implementation of the LCD send color function. For better performance this should use DMA transfer.
* In case of a DMA transfer a callback must be installed to notify LVGL about the end of the transfer.
*/
static void lcd_send_color(lv_display_t *disp, const uint8_t *cmd, size_t cmd_size, uint8_t *param, size_t param_size)
{
LV_UNUSED(disp);
while (lcd_bus_busy); /* wait until previous transfer is finished */
/* Set the SPI in 8-bit mode */
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
HAL_SPI_Init(&hspi1);
/* DCX low (command) */
HAL_GPIO_WritePin(LCD_DCX_GPIO_Port, LCD_DCX_Pin, GPIO_PIN_RESET);
/* CS low */
HAL_GPIO_WritePin(LCD_CS_GPIO_Port, LCD_CS_Pin, GPIO_PIN_RESET);
/* send command */
if (HAL_SPI_Transmit(&hspi1, cmd, cmd_size, BUS_SPI1_POLL_TIMEOUT) == HAL_OK) {
/* DCX high (data) */
HAL_GPIO_WritePin(LCD_DCX_GPIO_Port, LCD_DCX_Pin, GPIO_PIN_SET);
/* for color data use DMA transfer */
/* Set the SPI in 16-bit mode to match endianness */
hspi1.Init.DataSize = SPI_DATASIZE_16BIT;
HAL_SPI_Init(&hspi1);
lcd_bus_busy = 1;
HAL_SPI_Transmit_DMA(&hspi1, param, (uint16_t)param_size / 2);
/* NOTE: CS will be reset in the transfer ready callback */
}
}
#. Add the LVGL_Task() function. Replace the ``lv_st7789_create()`` call with the appropriate driver. You can change the default orientation by adjusting the parameter of ``lv_display_set_rotation()``. You will also need to create the display buffers here. This example uses a double buffering scheme with 1/10th size partial buffers. In most cases this is a good compromise between the required memory size and performance, but you are free to experiment with other settings.
.. code-block:: c
void LVGL_Task(void const *argument)
{
/* Initialize LVGL */
lv_init();
/* Initialize LCD I/O */
if (lcd_io_init() != 0)
return;
/* Create the LVGL display object and the LCD display driver */
lcd_disp = lv_st7789_create(LCD_H_RES, LCD_V_RES, LV_LCD_FLAG_NONE, lcd_send_cmd, lcd_send_color);
lv_display_set_rotation(lcd_disp, LV_DISPLAY_ROTATION_270);
/* Allocate draw buffers on the heap. In this example we use two partial buffers of 1/10th size of the screen */
lv_color_t * buf1 = NULL;
lv_color_t * buf2 = NULL;
uint32_t buf_size = LCD_H_RES * LCD_V_RES / 10 * lv_color_format_get_size(lv_display_get_color_format(lcd_disp));
buf1 = lv_malloc(buf_size);
if(buf1 == NULL) {
LV_LOG_ERROR("display draw buffer malloc failed");
return;
}
buf2 = lv_malloc(buf_size);
if(buf2 == NULL) {
LV_LOG_ERROR("display buffer malloc failed");
lv_free(buf1);
return;
}
lv_display_set_buffers(lcd_disp, buf1, buf2, buf_size, LV_DISPLAY_RENDER_MODE_PARTIAL);
ui_init(lcd_disp);
for(;;) {
/* The task running lv_timer_handler should have lower priority than that running `lv_tick_inc` */
lv_timer_handler();
/* raise the task priority of LVGL and/or reduce the handler period can improve the performance */
osDelay(10);
}
}
#. All that's left is to implement ``ui_init()`` to create the screen. Here's a simple "Hello World" example:
.. code-block:: c
void ui_init(lv_display_t *disp)
{
lv_obj_t *obj;
/* set screen background to white */
lv_obj_t *scr = lv_screen_active();
lv_obj_set_style_bg_color(scr, lv_color_white(), 0);
lv_obj_set_style_bg_opa(scr, LV_OPA_100, 0);
/* create label */
obj = lv_label_create(scr);
lv_obj_set_align(widget, LV_ALIGN_CENTER);
lv_obj_set_height(widget, LV_SIZE_CONTENT);
lv_obj_set_width(widget, LV_SIZE_CONTENT);
lv_obj_set_style_text_font(widget, &lv_font_montserrat_14, 0);
lv_obj_set_style_text_color(widget, lv_color_black(), 0);
lv_label_set_text(widget, "Hello World!");
}

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.. _renesas_glcdc:
=============
Renesas GLCDC
=============
Overview
--------
.. image:: /misc/renesas/glcdc.png
:alt: Architectural overview of Renesas GLCDC
:align: center
<br/>
GLCDC is a multi-stage graphics output peripheral used in Renesas MCUs.
It is designed to automatically generate timing and data signals for different LCD panels.
- Supports LCD panels with RGB interface (up to 24 bits) and sync signals (HSYNC, VSYNC and Data Enable optional)
- Supports various color formats for input graphics planes (RGB888, ARGB8888, RGB565, ARGB1555, ARGB4444, CLUT8, CLUT4, CLUT1)
- Supports the Color Look-Up Table (CLUT) usage for input graphics planes (ARGB8888) with 512 words (32 bits/word)
- Supports various color formats for output (RGB888, RGB666, RGB565, Serial RGB888)
- Can input two graphics planes on top of the background plane and blend them on the screen
- Generates a dot clock to the panel. The clock source is selectable from internal or external (LCD_EXTCLK)
- Supports brightness adjustment, contrast adjustment, and gamma correction
- Supports GLCDC interrupts to handle frame-buffer switching or underflow detection
Setting up a project and further integration with Renesas' ecosystem is described in detail on :ref:`page Renesas <renesas>`.
Check out the following repositories for ready-to-use examples:
- `EK-RA8D1 <https://github.com/lvgl/lv_port_renesas_ek-ra8d1>`__
- `EK-RA6M3G <https://github.com/lvgl/lv_port_renesas_ek-ra6m3g>`__
- `RX72N Envision Kit <https://github.com/lvgl/lv_port_renesas_rx72n-envision-kit>`__
Prerequisites
-------------
- This diver relies on code generated by e² studio. Missing the step while setting up the project will cause a compilation error.
- Activate the diver by setting :c:macro:`LV_USE_RENESAS_GLCDC` to ``1`` in your *"lv_conf.h"*.
Usage
-----
There is no need to implement any platform-specific functions.
The following code demonstrates using the diver in :cpp:enumerator:`LV_DISPLAY_RENDER_MODE_DIRECT` mode.
.. code-block:: c
lv_display_t * disp = lv_renesas_glcdc_direct_create();
lv_display_set_default(disp);
To use the driver in :cpp:enumerator:`LV_DISPLAY_RENDER_MODE_PARTIAL` mode, an extra buffer must be allocated,
preferably in the fastest available memory region.
Buffer swapping can be activated by passing a second buffer of same size instead of the :cpp:expr:`NULL` argument.
.. code-block:: c
static lv_color_t partial_draw_buf[DISPLAY_HSIZE_INPUT0 * DISPLAY_VSIZE_INPUT0 / 10] BSP_PLACE_IN_SECTION(".sdram") BSP_ALIGN_VARIABLE(1024);
lv_display_t * disp = lv_renesas_glcdc_partial_create(partial_draw_buf, NULL, sizeof(partial_draw_buf));
lv_display_set_default(disp);
.. note::
Partial mode can be activated via the macro in ``src/board_init.c`` file of the demo projects.
Screen rotation
"""""""""""""""
Software based screen rotation is supported in partial mode. It uses the common API, no extra configuration is required:
.. code-block:: c
lv_display_set_rotation(lv_display_get_default(), LV_DISP_ROTATION_90);
/* OR */
lv_display_set_rotation(lv_display_get_default(), LV_DISP_ROTATION_180);
/* OR */
lv_display_set_rotation(lv_display_get_default(), LV_DISP_ROTATION_270);
Make sure the heap is large enough, as a buffer with the same size as the partial buffer will be allocated.

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============================
ST7735 LCD Controller driver
============================
Overview
--------
The `ST7735S <https://www.buydisplay.com/download/ic/ST7735S.pdf>`__ is a single-chip controller/driver for 262K-color, graphic type TFT-LCD. It consists of 396
source line and 162 gate line driving circuits. This chip is capable of connecting directly to an external
microprocessor, and accepts Serial Peripheral Interface (SPI), 8-bit/9-bit/16-bit/18-bit parallel interface.
Display data can be stored in the on-chip display data RAM of 132 x 162 x 18 bits. It can perform display data
RAM read/write operation with no external operation clock to minimize power consumption. In addition,
because of the integrated power supply circuits necessary to drive liquid crystal, it is possible to make a
display system with fewer components.
The ST7735 LCD controller `driver <https://github.com/lvgl/lvgl/src/drivers/display/st7735>`__ is a platform-agnostic driver, based on the `generic MIPI driver <https://github.com/lvgl/lvgl/doc/integration/drivers/display/gen_mipi.rst>`__.
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
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.
Prerequisites
-------------
There are no prerequisites.
Configuring the driver
----------------------
Enable the ST7735 driver support in lv_conf.h, by cmake compiler define or by KConfig
.. code-block:: c
#define LV_USE_ST7735 1
Usage
-----
You need to implement two platform-dependent functions:
.. code-block:: c
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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)
{
...
}
/* 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. */
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)
{
...
}
To create an ST7735-based display use the function
.. code-block:: c
/**
* Create an LCD display with ST7735 driver
* @param hor_res horizontal resolution
* @param ver_res vertical resolution
* @param flags default configuration settings (mirror, RGB ordering, etc.)
* @param send_cmd platform-dependent function to send a command to the LCD controller (usually uses polling transfer)
* @param send_color platform-dependent function to send pixel data to the LCD controller (usually uses DMA transfer: must implement a 'ready' callback)
* @return pointer to the created display
*/
lv_display_t * lv_st7735_create(uint32_t hor_res, uint32_t ver_res, lv_lcd_flag_t flags,
lv_st7735_send_cmd_cb_t send_cmd_cb, lv_st7735_send_color_cb_t send_color_cb);
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>`__.
.. note::
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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============================
ST7789 LCD Controller driver
============================
Overview
--------
The `ST7789 <https://www.buydisplay.com/download/ic/ST7789.pdf>`__ is a single-chip controller/driver for 262K-color, graphic type TFT-LCD. It consists of 720
source line and 320 gate line driving circuits. This chip is capable of connecting directly to an external
microprocessor, and accepts, 8-bits/9-bits/16-bits/18-bits parallel interface. Display data can be stored in the
on-chip display data RAM of 240x320x18 bits. It can perform display data RAM read/write operation with no
external operation clock to minimize power consumption. In addition, because of the integrated power supply
circuit necessary to drive liquid crystal; it is possible to make a display system with the fewest components.
The ST7789 LCD controller `driver <https://github.com/lvgl/lvgl/src/drivers/display/st7789>`__ is a platform-agnostic driver, based on the `generic MIPI driver <https://github.com/lvgl/lvgl/doc/integration/drivers/display/gen_mipi.rst>`__.
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
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.
Prerequisites
-------------
There are no prerequisites.
Configuring the driver
----------------------
Enable the ST7789 driver support in lv_conf.h, by cmake compiler define or by KConfig
.. code-block:: c
#define LV_USE_ST7789 1
Usage
-----
You need to implement two platform-dependent functions:
.. code-block:: c
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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)
{
...
}
/* 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. */
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)
{
...
}
To create an ST7789-based display use the function
.. code-block:: c
/**
* Create an LCD display with ST7789 driver
* @param hor_res horizontal resolution
* @param ver_res vertical resolution
* @param flags default configuration settings (mirror, RGB ordering, etc.)
* @param send_cmd platform-dependent function to send a command to the LCD controller (usually uses polling transfer)
* @param send_color platform-dependent function to send pixel data to the LCD controller (usually uses DMA transfer: must implement a 'ready' callback)
* @return pointer to the created display
*/
lv_display_t * lv_st7789_create(uint32_t hor_res, uint32_t ver_res, lv_lcd_flag_t flags,
lv_st7789_send_cmd_cb_t send_cmd_cb, lv_st7789_send_color_cb_t send_color_cb);
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>`__.
.. note::
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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============================
ST7796 LCD Controller driver
============================
Overview
--------
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
source lines and 480 gate lines driving circuits. The ST7796S is capable of connecting directly to an external
microprocessor, and accepts 8-bit/9-bit/16-bit/18-bit parallel interface, SPI, and the ST7796S also provides
MIPI interface. Display data can be stored in the on-chip display data RAM of 320x480x18 bits. It can perform
display data RAM read-/write-operation with no external clock to minimize power consumption. In addition,
because of the integrated power supply circuit necessary to drive liquid crystal; it is possible to make a display
system with fewest components.
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>`__.
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
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.
Prerequisites
-------------
There are no prerequisites.
Configuring the driver
----------------------
Enable the ST7796 driver support in lv_conf.h, by cmake compiler define or by KConfig
.. code-block:: c
#define LV_USE_ST7796 1
Usage
-----
You need to implement two platform-dependent functions:
.. code-block:: c
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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)
{
...
}
/* 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. */
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)
{
...
}
To create an ST7796-based display use the function
.. code-block:: c
/**
* Create an LCD display with ST7796 driver
* @param hor_res horizontal resolution
* @param ver_res vertical resolution
* @param flags default configuration settings (mirror, RGB ordering, etc.)
* @param send_cmd platform-dependent function to send a command to the LCD controller (usually uses polling transfer)
* @param send_color platform-dependent function to send pixel data to the LCD controller (usually uses DMA transfer: must implement a 'ready' callback)
* @return pointer to the created display
*/
lv_display_t * lv_st7796_create(uint32_t hor_res, uint32_t ver_res, lv_lcd_flag_t flags,
lv_st7796_send_cmd_cb_t send_cmd_cb, lv_st7796_send_color_cb_t send_color_cb);
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>`__.
.. note::
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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=================
STM32 LTDC Driver
=================
Some STM32s have a specialized peripheral for driving
displays called LTDC (LCD-TFT display controller).
Usage Modes With LVGL
*********************
The driver within LVGL is designed to work with an
already-configured LTDC peripheral. It relies on the
HAL to detect information about the configuration.
The color format of the created LVGL display will
match the LTDC layer's color format. Use STM32CubeIDE
or STM32CubeMX to generate LTDC initialization code.
There are some different use cases for LVGL's driver.
All permutations of the below options are well supported.
- single or double buffered
- direct or partial render mode
- OS and no OS
- paralellized flushing with DMA2D (only for partial render mode)
If OS is enabled, a synchronization primitive will be used to
give the thread a chance to yield to other threads while blocked,
improving CPU utilization. See :c:macro:`LV_USE_OS` in your lv_conf.h
LTDC Layers
***********
This driver creates an LVGL display
which is only concerned with a specific layer of the LTDC peripheral, meaning
two LVGL LTDC displays can be created and operate independently on the separate
layers.
Direct Render Mode
******************
For direct render mode, invoke :cpp:func:`lv_st_ltdc_create_direct` like this:
.. code-block:: c
void * my_ltdc_framebuffer_address = (void *)0x20000000u;
uint32_t my_ltdc_layer_index = 0; /* typically 0 or 1 */
lv_display_t * disp = lv_st_ltdc_create_direct(my_ltdc_framebuffer_address,
optional_other_full_size_buffer,
my_ltdc_layer_index);
``my_ltdc_framebuffer_address`` is the framebuffer configured for use by
LTDC. ``optional_other_full_size_buffer`` can be another buffer which is the same
size as the default framebuffer for double-buffered
mode, or ``NULL`` otherwise. ``my_ltdc_layer_index`` is the layer index of the
LTDC layer to create the display for.
For the best visial results, ``optional_other_full_size_buffer`` should be used
if enough memory is available. Single-buffered mode is what you should use
if memory is very scarce. If there is almost enough memory for double-buffered
direct mode, but not quite, then use partial render mode.
Partial Render Mode
*******************
For partial render mode, invoke :cpp:func:`lv_st_ltdc_create_partial` like this:
.. code-block:: c
static uint8_t partial_buf1[65536];
static uint8_t optional_partial_buf2[65536];
uint32_t my_ltdc_layer_index = 0; /* typically 0 or 1 */
lv_display_t * disp = lv_st_ltdc_create_partial(partial_buf1,
optional_partial_buf2,
65536,
my_ltdc_layer_index);
The driver will use the information in the LTDC layer configuration to find the
layer's framebuffer and flush to it.
Providing a second partial buffer can improve CPU utilization and increase
performance compared to
a single buffer if :c:macro:`LV_ST_LTDC_USE_DMA2D_FLUSH` is enabled.
DMA2D
*****
:c:macro:`LV_ST_LTDC_USE_DMA2D_FLUSH` can be enabled to use DMA2D to flush
partial buffers in parallel with other LVGL tasks, whether or not OS is
enabled. If the display is not partial, then there is no need to enable this
option.
It must not be enabled at the same time as :c:macro:`LV_USE_DRAW_DMA2D`.
See the :ref:`DMA2D support <dma2d>`.
.. admonition:: Further Reading
You may be interested in enabling the :ref:`Nema GFX renderer <stm32_nema_gfx>`
if your STM32 has a GPU which is supported by Nema GFX.
`lv_port_riverdi_stm32u5 <https://github.com/lvgl/lv_port_riverdi_stm32u5>`__
is a way to quick way to get started with LTDC on LVGL.