# ST7796 LCD Controller Driver (/integration/external_display_controllers/st7796)



Overview [#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/tree/master/src/drivers/display/st7796) is a
platform-agnostic driver, based on the generic MIPI driver.  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 [#prerequisites]

There are no prerequisites.

Configuring the Driver [#configuring-the-driver]

Enable the ST7796 driver support in lv\_conf.h, by cmake compiler define or by KConfig:

```c title=" " lineNumbers=1
#define LV_USE_ST7796  1
```

Usage [#usage]

You need to implement two platform-dependent functions:

```c title=" " lineNumbers=1
/* Send short command to the LCD. This function shall wait until the transaction finishes. */
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 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. */
void 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

```c title=" " lineNumbers=1
/**
 * 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.