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new 96a49bc7f78 drivers/lcd: Add ST7796 TFT LCD framebuffer driver
96a49bc7f78 is described below
commit 96a49bc7f78b2ca6271e919e16327253d06ec3e3
Author: vrmay23 <[email protected]>
AuthorDate: Sun Feb 1 20:38:48 2026 +0100
drivers/lcd: Add ST7796 TFT LCD framebuffer driver
Add support for ST7796 TFT LCD controller (320x480). The driver
implements the NuttX framebuffer interface for SPI-connected displays.
Features:
- SPI interface with CONFIG_SPI_CMDDATA for D/C pin control;
- RGB565 (16-bit) and RGB666 (18-bit) color formats;
- Runtime rotation support (0, 90, 180, 270 degrees) via MADCTL;
- Board-provided configuration via st7796_config_s structure;
- Partial screen update via updatearea for efficient rendering;
- Persistent swap buffer to avoid per-frame allocations;
- Proper ST7796S initialization sequence with documented timing;
The driver uses a board-provided configuration structure allowing
flexible setup of resolution, SPI frequency, color depth, and
initial MADCTL value without requiring Kconfig options in the
generic driver.
Architecture changes in this revision as per request:
- Moved internal register commands to .c file (private)
- Moved MADCTL bit definitions to .c file (private)
- Moved struct st7796_cmd_s to .c file (private)
- Converted MADCTL orientation macros to absolute values
- Moved CONFIG_SPI_CMDDATA error check to beginning of file
- Removed duplicated CONFIG_SPI_CMDDATA guards
- Public header contains only board configuration API
- Changed the Kconfig auto-select FB from 'select' to 'depends on'
Tested with LVGL graphics library on STM32H753ZI board (my own port).
Signed-off-by: Vinicius May <[email protected]>
---
drivers/lcd/CMakeLists.txt | 4 +
drivers/lcd/Kconfig | 8 +
drivers/lcd/Make.defs | 4 +
drivers/lcd/st7796.c | 999 +++++++++++++++++++++++++++++++++++++++++++++
include/nuttx/lcd/st7796.h | 178 ++++++++
include/nuttx/video/fb.h | 6 +
6 files changed, 1199 insertions(+)
diff --git a/drivers/lcd/CMakeLists.txt b/drivers/lcd/CMakeLists.txt
index 0bd152f9518..68e4e0ef4c6 100644
--- a/drivers/lcd/CMakeLists.txt
+++ b/drivers/lcd/CMakeLists.txt
@@ -145,6 +145,10 @@ if(CONFIG_LCD)
list(APPEND SRCS st7789.c)
endif()
+ if(CONFIG_LCD_ST7796)
+ list(APPEND SRCS st7796.c)
+ endif()
+
if(CONFIG_LCD_GC9A01)
list(APPEND SRCS gc9a01.c)
endif()
diff --git a/drivers/lcd/Kconfig b/drivers/lcd/Kconfig
index b6894163a31..ef216e5568b 100644
--- a/drivers/lcd/Kconfig
+++ b/drivers/lcd/Kconfig
@@ -827,6 +827,14 @@ config LCD_ST7789_DATA_ENDIAN_LITTLE
endif # LCD_ST7789
+config LCD_ST7796
+ bool "ST7796 LCD Display"
+ default n
+ depends on SPI
+ depends on LCD_FRAMEBUFFER
+ ---help---
+ Enable support for ST7796 LCD display driver.
+
config LCD_GC9A01
bool "Galaxycore GC9A01 TFT Controller"
default n
diff --git a/drivers/lcd/Make.defs b/drivers/lcd/Make.defs
index 95a4b414f0a..081b5020195 100644
--- a/drivers/lcd/Make.defs
+++ b/drivers/lcd/Make.defs
@@ -143,6 +143,10 @@ ifeq ($(CONFIG_LCD_ST7789),y)
CSRCS += st7789.c
endif
+ifeq ($(CONFIG_LCD_ST7796),y)
+ CSRCS += st7796.c
+endif
+
ifeq ($(CONFIG_LCD_GC9A01),y)
CSRCS += gc9a01.c
endif
diff --git a/drivers/lcd/st7796.c b/drivers/lcd/st7796.c
new file mode 100644
index 00000000000..ea006519518
--- /dev/null
+++ b/drivers/lcd/st7796.c
@@ -0,0 +1,999 @@
+/****************************************************************************
+ * drivers/lcd/st7796.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/spi/spi.h>
+#include <nuttx/video/fb.h>
+#include <nuttx/kmalloc.h>
+#include <nuttx/clock.h>
+#include <nuttx/signal.h>
+#include <nuttx/lcd/st7796.h>
+
+#ifndef CONFIG_SPI_CMDDATA
+# error "CONFIG_SPI_CMDDATA must be enabled for ST7796"
+#endif
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* ST7796 Commands - Standard */
+
+#define ST7796_NOP 0x00 /* NOP */
+#define ST7796_SWRESET 0x01 /* Software Reset */
+#define ST7796_RDDID 0x04 /* Read Display ID */
+#define ST7796_RDDST 0x09 /* Read Display Status */
+#define ST7796_SLPIN 0x10 /* Sleep In */
+#define ST7796_SLPOUT 0x11 /* Sleep Out */
+#define ST7796_PTLON 0x12 /* Partial Display Mode On */
+#define ST7796_NORON 0x13 /* Normal Display Mode On */
+#define ST7796_RDIMGFMT 0x0a /* Read Display Image Format */
+#define ST7796_RDSELFDIAG 0x0f /* Read Display Self-Diagnostic Result */
+#define ST7796_INVOFF 0x20 /* Display Inversion Off */
+#define ST7796_INVON 0x21 /* Display Inversion On */
+#define ST7796_GAMMASET 0x26 /* Gamma Set */
+#define ST7796_DISPOFF 0x28 /* Display Off */
+#define ST7796_DISPON 0x29 /* Display On */
+#define ST7796_CASET 0x2a /* Column Address Set */
+#define ST7796_RASET 0x2b /* Row Address Set */
+#define ST7796_RAMWR 0x2c /* Memory Write */
+#define ST7796_RAMRD 0x2e /* Memory Read */
+#define ST7796_PTLAR 0x30 /* Partial Area */
+#define ST7796_VSCRDEF 0x33 /* Vertical Scrolling Definition */
+#define ST7796_TEOFF 0x34 /* Tearing Effect Line Off */
+#define ST7796_TEON 0x35 /* Tearing Effect Line On */
+#define ST7796_MADCTL 0x36 /* Memory Access Control */
+#define ST7796_VSCRSADD 0x37 /* Vertical Scrolling Start Address */
+#define ST7796_PIXFMT 0x3a /* Pixel Format Set */
+#define ST7796_WRDISPBRIGHT 0x51 /* Write Display Brightness */
+#define ST7796_RDDISPBRIGHT 0x52 /* Read Display Brightness */
+#define ST7796_WRCTRLD 0x53 /* Write Control Display */
+#define ST7796_RDCTRLD 0x54 /* Read Control Display */
+#define ST7796_WRCABC 0x55 /* Write Content Adaptive Brightness */
+#define ST7796_RDCABC 0x56 /* Read Content Adaptive Brightness */
+#define ST7796_WRCABCMIN 0x5e /* Write CABC Minimum Brightness */
+#define ST7796_RDCABCMIN 0x5f /* Read CABC Minimum Brightness */
+
+/* ST7796 Commands - Extended */
+
+#define ST7796_INVCTR 0xb4 /* Display Inversion Control */
+#define ST7796_DFC 0xb6 /* Display Function Control */
+#define ST7796_PWCTRL1 0xc0 /* Power Control 1 */
+#define ST7796_PWCTRL2 0xc1 /* Power Control 2 */
+#define ST7796_PWCTRL3 0xc2 /* Power Control 3 */
+#define ST7796_PWCTRL4 0xc3 /* Power Control 4 */
+#define ST7796_PWCTRL5 0xc4 /* Power Control 5 */
+#define ST7796_VCOM 0xc5 /* VCOM Control */
+#define ST7796_PWCTRL6 0xc6 /* Power Control 6 */
+#define ST7796_GAMMAPOS 0xe0 /* Positive Gamma Correction */
+#define ST7796_GAMMANEG 0xe1 /* Negative Gamma Correction */
+#define ST7796_DOCA 0xe9 /* Set DDB Write Address */
+#define ST7796_CSCON 0xf0 /* Command Set Control */
+
+/* ST7796 MADCTL bits */
+
+#define ST7796_MADCTL_MY 0x80 /* Row Address Order */
+#define ST7796_MADCTL_MX 0x40 /* Column Address Order */
+#define ST7796_MADCTL_MV 0x20 /* Row/Column Exchange */
+#define ST7796_MADCTL_ML 0x10 /* Vertical Refresh Order */
+#define ST7796_MADCTL_BGR 0x08 /* BGR color filter panel */
+#define ST7796_MADCTL_MH 0x04 /* Horizontal Refresh Order */
+
+/* Force SPI MODE 0 (CPOL=0, CPHA=0) - Standard for ST7796 */
+
+#define ST7796_SPIMODE SPIDEV_MODE0
+
+/* Bytes per pixel based on BPP */
+
+#define ST7796_BYTESPP(bpp) (((bpp) == 18) ? 3 : 2)
+
+/* Color format based on BPP */
+
+#define ST7796_COLORFMT(bpp) (((bpp) == 18) ? FB_FMT_RGB24 : \
+ FB_FMT_RGB16_565)
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/* Command sequence entry for initialization */
+
+struct st7796_cmd_s
+{
+ uint8_t cmd; /* Command byte */
+ FAR const uint8_t *data; /* Parameter data (NULL if no params) */
+ uint8_t len; /* Number of parameter bytes */
+ uint16_t delay_ms; /* Delay after command in milliseconds */
+};
+
+struct st7796_dev_s
+{
+ struct fb_vtable_s vtable;
+ FAR struct spi_dev_s *spi;
+ FAR uint8_t *fbmem;
+ FAR uint16_t *swap_buf; /* Persistent buffer for byte-swapping */
+ struct st7796_config_s config; /* Board-provided configuration */
+ uint16_t rotation; /* Current rotation in degrees */
+ bool power;
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int st7796_getvideoinfo(FAR struct fb_vtable_s *vtable,
+ FAR struct fb_videoinfo_s *vinfo);
+static int st7796_getplaneinfo(FAR struct fb_vtable_s *vtable, int planeno,
+ FAR struct fb_planeinfo_s *pinfo);
+static int st7796_updatearea(FAR struct fb_vtable_s *vtable,
+ FAR const struct fb_area_s *area);
+static int st7796_ioctl(FAR struct fb_vtable_s *vtable, int cmd,
+ unsigned long arg);
+static void st7796_select(FAR struct st7796_dev_s *priv);
+static void st7796_deselect(FAR struct st7796_dev_s *priv);
+static void st7796_sendcmd(FAR struct st7796_dev_s *priv, uint8_t cmd);
+static void st7796_senddata(FAR struct st7796_dev_s *priv,
+ FAR const uint8_t *data, size_t len);
+static void st7796_send_sequence(FAR struct st7796_dev_s *priv,
+ FAR const struct st7796_cmd_s *seq,
+ size_t count);
+static void st7796_setarea(FAR struct st7796_dev_s *priv,
+ uint16_t x0, uint16_t y0,
+ uint16_t x1, uint16_t y1);
+static void st7796_apply_rotation(FAR struct st7796_dev_s *priv);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static struct st7796_dev_s g_st7796dev;
+
+/* Initialization sequence data arrays
+ *
+ * ST7796S Register Configuration Reference:
+ *
+ * CSCON (Command Set Control):
+ * 0xc3, 0x96 - Enable extended command access (unlock)
+ * 0x3c, 0x69 - Disable extended command access (lock)
+ *
+ * PIXFMT (Pixel Format):
+ * 0x55 - RGB565 16bpp (0101 0101b: 16-bit RGB + 16-bit MCU)
+ *
+ * INVCTR (Display Inversion):
+ * 0x01 - Column inversion mode
+ *
+ * DFC (Display Function Control):
+ * 0x80 - Source output scan direction
+ * 0x02 - Gate output scan direction
+ * 0x3b - Number of lines (59 * 8 = 472 lines)
+ *
+ * CMD 0xE8 (Undocumented):
+ * Internal timing adjustment, from manufacturer reference
+ *
+ * PWCTRL2/3 (Power Control):
+ * 0x06 - VGH/VGL voltage setting
+ * 0xa7 - VCOM voltage adjustment
+ *
+ * VCOM:
+ * 0x18 - VCOM voltage for contrast tuning
+ *
+ * GAMMAPOS/GAMMANEG:
+ * 14-byte gamma correction curves for color linearity
+ *
+ * MADCTL values provided by board configuration
+ */
+
+static const uint8_t g_cscon1_data[] =
+{
+ 0xc3
+};
+
+static const uint8_t g_cscon2_data[] =
+{
+ 0x96
+};
+
+static const uint8_t g_pixfmt_data[] =
+{
+ 0x55
+};
+
+static const uint8_t g_invctr_data[] =
+{
+ 0x01
+};
+
+static const uint8_t g_dfc_data[] =
+{
+ 0x80, 0x02, 0x3b
+};
+
+static const uint8_t g_cmd_e8_data[] =
+{
+ 0x40, 0x8a, 0x00, 0x00, 0x29, 0x19, 0xa5, 0x33
+};
+
+static const uint8_t g_pwctrl2_data[] =
+{
+ 0x06
+};
+
+static const uint8_t g_pwctrl3_data[] =
+{
+ 0xa7
+};
+
+static const uint8_t g_vcom_data[] =
+{
+ 0x18
+};
+
+static const uint8_t g_gammapos_data[] =
+{
+ 0xf0, 0x09, 0x0b, 0x06, 0x04, 0x15,
+ 0x2f, 0x54, 0x42, 0x3c, 0x17, 0x14,
+ 0x18, 0x1b
+};
+
+static const uint8_t g_gammaneg_data[] =
+{
+ 0xf0, 0x09, 0x0b, 0x06, 0x04, 0x03,
+ 0x2d, 0x43, 0x42, 0x3b, 0x16, 0x14,
+ 0x17, 0x1b
+};
+
+static const uint8_t g_cscon3_data[] =
+{
+ 0x3c
+};
+
+static const uint8_t g_cscon4_data[] =
+{
+ 0x69
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: st7796_select
+ *
+ * Description:
+ * Select the SPI device, locking the bus and configuring SPI parameters.
+ * This function locks the SPI bus, sets the SPI mode, bit width, and
+ * frequency, then asserts the chip select signal.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_select(FAR struct st7796_dev_s *priv)
+{
+ SPI_LOCK(priv->spi, true);
+ SPI_SETMODE(priv->spi, ST7796_SPIMODE);
+ SPI_SETBITS(priv->spi, 8);
+ SPI_SETFREQUENCY(priv->spi, priv->config.frequency);
+ SPI_SELECT(priv->spi, SPIDEV_DISPLAY(0), true);
+}
+
+/****************************************************************************
+ * Name: st7796_deselect
+ *
+ * Description:
+ * Deselect the SPI device, releasing the chip select and unlocking the
+ * SPI bus for other devices.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_deselect(FAR struct st7796_dev_s *priv)
+{
+ SPI_SELECT(priv->spi, SPIDEV_DISPLAY(0), false);
+ SPI_LOCK(priv->spi, false);
+}
+
+/****************************************************************************
+ * Name: st7796_sendcmd
+ *
+ * Description:
+ * Send a command byte to the ST7796 display controller. The D/C (Data/
+ * Command) line is set to command mode before transmission.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ * cmd - Command byte to send
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_sendcmd(FAR struct st7796_dev_s *priv, uint8_t cmd)
+{
+ SPI_CMDDATA(priv->spi, SPIDEV_DISPLAY(0), true);
+ SPI_SEND(priv->spi, cmd);
+}
+
+/****************************************************************************
+ * Name: st7796_senddata
+ *
+ * Description:
+ * Send data bytes to the ST7796 display controller. The D/C (Data/
+ * Command) line is set to data mode before transmission.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ * data - Pointer to the data buffer to send
+ * len - Number of bytes to send
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_senddata(FAR struct st7796_dev_s *priv,
+ FAR const uint8_t *data, size_t len)
+{
+ if (len > 0 && data != NULL)
+ {
+ SPI_CMDDATA(priv->spi, SPIDEV_DISPLAY(0), false);
+ SPI_SNDBLOCK(priv->spi, data, len);
+ }
+}
+
+/****************************************************************************
+ * Name: st7796_send_sequence
+ *
+ * Description:
+ * Send a sequence of commands and data to the ST7796 display controller.
+ * Each entry in the sequence contains a command, optional data, and an
+ * optional delay. This function is typically used for display
+ * initialization.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ * seq - Pointer to an array of command/data sequence entries
+ * count - Number of entries in the sequence array
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_send_sequence(FAR struct st7796_dev_s *priv,
+ FAR const struct st7796_cmd_s *seq,
+ size_t count)
+{
+ size_t i;
+
+ lcdinfo("ST7796: Sending initialization sequence (%zu commands)\n", count);
+
+ for (i = 0; i < count; i++)
+ {
+ st7796_sendcmd(priv, seq[i].cmd);
+
+ if (seq[i].data != NULL && seq[i].len > 0)
+ {
+ st7796_senddata(priv, seq[i].data, seq[i].len);
+ }
+
+ if (seq[i].delay_ms > 0)
+ {
+ nxsig_usleep(seq[i].delay_ms * 1000);
+ }
+ }
+
+ lcdinfo("ST7796: Initialization sequence complete\n");
+}
+
+/****************************************************************************
+ * Name: st7796_setarea
+ *
+ * Description:
+ * Set the active drawing area on the ST7796 display. This defines the
+ * rectangular region where subsequent pixel data will be written. The
+ * function sends CASET (Column Address Set) and RASET (Row Address Set)
+ * commands to define the window boundaries.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ * x0 - Start column (left edge)
+ * y0 - Start row (top edge)
+ * x1 - End column (right edge, inclusive)
+ * y1 - End row (bottom edge, inclusive)
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_setarea(FAR struct st7796_dev_s *priv,
+ uint16_t x0, uint16_t y0,
+ uint16_t x1, uint16_t y1)
+{
+ uint8_t data[4];
+
+ st7796_sendcmd(priv, ST7796_CASET);
+ data[0] = (x0 >> 8) & 0xff;
+ data[1] = x0 & 0xff;
+ data[2] = (x1 >> 8) & 0xff;
+ data[3] = x1 & 0xff;
+ st7796_senddata(priv, data, 4);
+
+ st7796_sendcmd(priv, ST7796_RASET);
+ data[0] = (y0 >> 8) & 0xff;
+ data[1] = y0 & 0xff;
+ data[2] = (y1 >> 8) & 0xff;
+ data[3] = y1 & 0xff;
+ st7796_senddata(priv, data, 4);
+}
+
+/****************************************************************************
+ * Name: st7796_apply_rotation
+ *
+ * Description:
+ * Apply rotation by modifying the MADCTL register. This function
+ * calculates the appropriate MADCTL value based on the base orientation
+ * and the requested rotation angle, then sends it to the display.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ *
+ * Returned Value:
+ * None
+ *
+ ****************************************************************************/
+
+static void st7796_apply_rotation(FAR struct st7796_dev_s *priv)
+{
+ uint8_t madctl;
+ uint8_t data[1];
+
+ /* Start with base MADCTL from config */
+
+ madctl = priv->config.madctl;
+
+ /* Apply rotation by modifying MX/MY bits */
+
+ switch (priv->rotation)
+ {
+ case 0:
+
+ /* No rotation - use base MADCTL as-is */
+
+ break;
+
+ case 90:
+
+ /* 90 degrees: swap MV and toggle MX */
+
+ madctl ^= (ST7796_MADCTL_MV | ST7796_MADCTL_MX);
+ break;
+
+ case 180:
+
+ /* 180 degrees: toggle both MX and MY */
+
+ madctl ^= (ST7796_MADCTL_MX | ST7796_MADCTL_MY);
+ break;
+
+ case 270:
+
+ /* 270 degrees: swap MV and toggle MY */
+
+ madctl ^= (ST7796_MADCTL_MV | ST7796_MADCTL_MY);
+ break;
+
+ default:
+ lcdwarn("ST7796: Invalid rotation %d, using 0\n", priv->rotation);
+ priv->rotation = 0;
+ break;
+ }
+
+ /* Send MADCTL command */
+
+ data[0] = madctl;
+
+ st7796_select(priv);
+ st7796_sendcmd(priv, ST7796_MADCTL);
+ st7796_senddata(priv, data, 1);
+ st7796_deselect(priv);
+
+ lcdinfo("ST7796: Applied rotation %d (MADCTL=0x%02x)\n",
+ priv->rotation, madctl);
+}
+
+/****************************************************************************
+ * Name: st7796_getvideoinfo
+ *
+ * Description:
+ * Get information about the video controller and the configuration of
+ * the video plane. This is part of the framebuffer interface required
+ * by NuttX.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * vinfo - Pointer to the video info structure to be filled
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int st7796_getvideoinfo(FAR struct fb_vtable_s *vtable,
+ FAR struct fb_videoinfo_s *vinfo)
+{
+ FAR struct st7796_dev_s *priv = (FAR struct st7796_dev_s *)vtable;
+
+ lcdinfo("ST7796: getvideoinfo\n");
+
+ vinfo->fmt = ST7796_COLORFMT(priv->config.bpp);
+ vinfo->xres = priv->config.xres;
+ vinfo->yres = priv->config.yres;
+ vinfo->nplanes = 1;
+
+ return OK;
+}
+
+/****************************************************************************
+ * Name: st7796_getplaneinfo
+ *
+ * Description:
+ * Get information about the framebuffer plane. Returns details about
+ * the framebuffer memory, stride, bits per pixel, and virtual
+ * resolution. This is part of the framebuffer interface required by
+ * NuttX.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * planeno - Plane number (must be 0 for this single-plane display)
+ * pinfo - Pointer to the plane info structure to be filled
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int st7796_getplaneinfo(FAR struct fb_vtable_s *vtable, int planeno,
+ FAR struct fb_planeinfo_s *pinfo)
+{
+ FAR struct st7796_dev_s *priv = (FAR struct st7796_dev_s *)vtable;
+ size_t fbsize;
+ uint8_t bytespp;
+
+ lcdinfo("ST7796: getplaneinfo - plane %d\n", planeno);
+
+ bytespp = ST7796_BYTESPP(priv->config.bpp);
+ fbsize = priv->config.xres * priv->config.yres * bytespp;
+
+ pinfo->fbmem = priv->fbmem;
+ pinfo->fblen = fbsize;
+ pinfo->stride = priv->config.xres * bytespp;
+ pinfo->bpp = priv->config.bpp;
+ pinfo->xres_virtual = priv->config.xres;
+ pinfo->yres_virtual = priv->config.yres;
+ pinfo->xoffset = 0;
+ pinfo->yoffset = 0;
+
+ return OK;
+}
+
+/****************************************************************************
+ * Name: st7796_updatearea
+ *
+ * Description:
+ * Update a rectangular area of the display from the framebuffer. This
+ * function transfers pixel data from the in-memory framebuffer to the
+ * ST7796 display controller via SPI. The pixel data is byte-swapped
+ * from little-endian (CPU native) to big-endian (display native) format
+ * during transfer.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * area - Pointer to structure describing the rectangular area to
+ * update (x, y, width, height)
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int st7796_updatearea(FAR struct fb_vtable_s *vtable,
+ FAR const struct fb_area_s *area)
+{
+ FAR struct st7796_dev_s *priv = (FAR struct st7796_dev_s *)vtable;
+ FAR uint16_t *src_fbptr;
+ size_t row_size_pixels;
+ uint8_t bytespp;
+ int row;
+ int i;
+
+ lcdinfo("ST7796: updatearea - x=%d y=%d w=%d h=%d\n",
+ area->x, area->y, area->w, area->h);
+
+ bytespp = ST7796_BYTESPP(priv->config.bpp);
+
+ st7796_select(priv);
+ st7796_setarea(priv, area->x, area->y,
+ area->x + area->w - 1,
+ area->y + area->h - 1);
+
+ st7796_sendcmd(priv, ST7796_RAMWR);
+
+ SPI_CMDDATA(priv->spi, SPIDEV_DISPLAY(0), false);
+
+ row_size_pixels = area->w;
+ src_fbptr = (FAR uint16_t *)
+ (priv->fbmem +
+ (area->y * priv->config.xres + area->x) * bytespp);
+
+ for (row = 0; row < area->h; row++)
+ {
+ for (i = 0; i < row_size_pixels; i++)
+ {
+ uint16_t pixel = src_fbptr[i];
+ priv->swap_buf[i] = (pixel << 8) | (pixel >> 8);
+ }
+
+ SPI_SNDBLOCK(priv->spi, (FAR const uint8_t *)priv->swap_buf,
+ row_size_pixels * bytespp);
+
+ src_fbptr += priv->config.xres;
+ }
+
+ st7796_deselect(priv);
+
+ return OK;
+}
+
+/****************************************************************************
+ * Name: st7796_ioctl
+ *
+ * Description:
+ * Handle framebuffer ioctl commands. Supports rotation control via
+ * FBIOSET_ROTATION and FBIOGET_ROTATION commands.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * cmd - ioctl command
+ * arg - ioctl argument
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int st7796_ioctl(FAR struct fb_vtable_s *vtable, int cmd,
+ unsigned long arg)
+{
+ FAR struct st7796_dev_s *priv = (FAR struct st7796_dev_s *)vtable;
+ int ret = OK;
+
+ switch (cmd)
+ {
+ case FBIOSET_ROTATION:
+ {
+ uint16_t rotation = (uint16_t)arg;
+
+ /* Validate rotation value */
+
+ if (rotation != 0 && rotation != 90 &&
+ rotation != 180 && rotation != 270)
+ {
+ lcderr("ERROR: Invalid rotation %d\n", rotation);
+ ret = -EINVAL;
+ break;
+ }
+
+ priv->rotation = rotation;
+ st7796_apply_rotation(priv);
+ }
+ break;
+
+ case FBIOGET_ROTATION:
+ {
+ FAR uint16_t *rotation = (FAR uint16_t *)arg;
+
+ if (rotation == NULL)
+ {
+ ret = -EINVAL;
+ break;
+ }
+
+ *rotation = priv->rotation;
+ }
+ break;
+
+ case FBIO_UPDATE:
+ {
+ FAR struct fb_area_s *area = (FAR struct fb_area_s *)arg;
+ ret = st7796_updatearea(vtable, area);
+ }
+ break;
+
+ default:
+ ret = -ENOTTY;
+ break;
+ }
+
+ return ret;
+}
+
+/****************************************************************************
+ * Name: st7796_init_display
+ *
+ * Description:
+ * Initialize the ST7796 display hardware with the provided configuration.
+ * This sends the initialization sequence and configures MADCTL based on
+ * board-provided settings.
+ *
+ * Input Parameters:
+ * priv - Reference to the ST7796 device structure
+ *
+ * Returned Value:
+ * None
+ *
+ * Timing requirements from ST7796S datasheet section 9.16:
+ *
+ * SWRESET: 120ms minimum recovery time (using 150ms for margin)
+ * SLPOUT: 120ms minimum for DC-DC and oscillator stabilization
+ * INVON: No minimum specified, 10ms for safety
+ * NORON: No minimum specified, 10ms for safety
+ * DISPON: Frame memory must be written first, 120ms for stabilization
+ *
+ * Sequence follows recommended power-on flow:
+ * 1. Software reset
+ * 2. Exit sleep mode
+ * 3. Unlock extended registers (CSCON)
+ * 4. Configure display parameters (including board-provided MADCTL)
+ * 5. Lock extended registers (CSCON)
+ * 6. Enable inversion and normal mode
+ * 7. Turn on display
+ *
+ ****************************************************************************/
+
+static void st7796_init_display(FAR struct st7796_dev_s *priv)
+{
+ uint8_t madctl_data[1];
+
+ /* MADCTL value from board configuration */
+
+ madctl_data[0] = priv->config.madctl;
+
+ /* Initialization sequence - Part 1: Reset and wake */
+
+ static const struct st7796_cmd_s init_seq_part1[] =
+ {
+ { ST7796_SWRESET, NULL, 0, 150 },
+ { ST7796_SLPOUT, NULL, 0, 150 },
+ { ST7796_CSCON, g_cscon1_data, 1, 0 },
+ { ST7796_CSCON, g_cscon2_data, 1, 0 },
+ };
+
+ /* Initialization sequence - Part 2: Configuration (after MADCTL) */
+
+ static const struct st7796_cmd_s init_seq_part2[] =
+ {
+ { ST7796_PIXFMT, g_pixfmt_data, 1, 0 },
+ { ST7796_INVCTR, g_invctr_data, 1, 0 },
+ { ST7796_DFC, g_dfc_data, 3, 0 },
+ { 0xe8, g_cmd_e8_data, 8, 0 },
+ { ST7796_PWCTRL2, g_pwctrl2_data, 1, 0 },
+ { ST7796_PWCTRL3, g_pwctrl3_data, 1, 0 },
+ { ST7796_VCOM, g_vcom_data, 1, 0 },
+ { ST7796_GAMMAPOS, g_gammapos_data, 14, 0 },
+ { ST7796_GAMMANEG, g_gammaneg_data, 14, 0 },
+ { ST7796_CSCON, g_cscon3_data, 1, 0 },
+ { ST7796_CSCON, g_cscon4_data, 1, 0 },
+ { ST7796_INVON, NULL, 0, 10 },
+ { ST7796_NORON, NULL, 0, 10 },
+ { ST7796_DISPON, NULL, 0, 120 },
+ };
+
+ st7796_select(priv);
+
+ /* Send part 1: Reset and unlock */
+
+ st7796_send_sequence(priv, init_seq_part1,
+ sizeof(init_seq_part1) / sizeof(struct st7796_cmd_s));
+
+ /* Send MADCTL with board-provided value */
+
+ st7796_sendcmd(priv, ST7796_MADCTL);
+ st7796_senddata(priv, madctl_data, 1);
+
+ /* Send part 2: Configuration and enable */
+
+ st7796_send_sequence(priv, init_seq_part2,
+ sizeof(init_seq_part2) / sizeof(struct st7796_cmd_s));
+
+ st7796_deselect(priv);
+
+ lcdinfo("ST7796: Display initialized (MADCTL=0x%02x)\n",
+ priv->config.madctl);
+
+ /* Apply initial rotation if configured */
+
+ if (priv->rotation != 0)
+ {
+ st7796_apply_rotation(priv);
+ }
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: st7796_fbinitialize
+ *
+ * Description:
+ * Initialize the ST7796 LCD controller and framebuffer driver. This
+ * function allocates the framebuffer memory, initializes the driver
+ * structure, sends the display initialization sequence, and returns
+ * a pointer to the framebuffer virtual table for use with the NuttX
+ * framebuffer interface.
+ *
+ * Input Parameters:
+ * spi - Reference to the SPI driver structure to use for communication
+ * config - Board-specific configuration (frequency, resolution, etc.)
+ *
+ * Returned Value:
+ * On success, a pointer to the framebuffer virtual table is returned.
+ * On failure, NULL is returned.
+ *
+ ****************************************************************************/
+
+FAR struct fb_vtable_s *st7796_fbinitialize(FAR struct spi_dev_s *spi,
+ FAR const struct st7796_config_s
+ *config)
+{
+ FAR struct st7796_dev_s *priv = &g_st7796dev;
+ size_t fbsize;
+ uint8_t bytespp;
+
+ DEBUGASSERT(spi != NULL && config != NULL);
+
+ lcdinfo("ST7796: Initializing framebuffer driver\n");
+ lcdinfo("ST7796: Resolution: %dx%d @ %d bpp\n",
+ config->xres, config->yres, config->bpp);
+ lcdinfo("ST7796: SPI Frequency: %lu Hz\n",
+ (unsigned long)config->frequency);
+ lcdinfo("ST7796: MADCTL: 0x%02x, Rotation: %d\n",
+ config->madctl, config->rotation);
+
+ /* Copy configuration */
+
+ memcpy(&priv->config, config, sizeof(struct st7796_config_s));
+
+ /* Set initial rotation from config */
+
+ priv->rotation = config->rotation;
+
+ /* Calculate sizes */
+
+ bytespp = ST7796_BYTESPP(config->bpp);
+ fbsize = config->xres * config->yres * bytespp;
+
+ /* Allocate framebuffer memory */
+
+ priv->fbmem = (FAR uint8_t *)kmm_zalloc(fbsize);
+ if (priv->fbmem == NULL)
+ {
+ lcderr("ERROR: Failed to allocate framebuffer (%zu bytes)\n", fbsize);
+ return NULL;
+ }
+
+ /* Allocate persistent row swap buffer to avoid malloc in updatearea */
+
+ priv->swap_buf = (FAR uint16_t *)kmm_malloc(config->xres * bytespp);
+ if (priv->swap_buf == NULL)
+ {
+ lcderr("ERROR: Failed to allocate swap buffer\n");
+ kmm_free(priv->fbmem);
+ return NULL;
+ }
+
+ /* Initialize driver structure */
+
+ priv->vtable.getvideoinfo = st7796_getvideoinfo;
+ priv->vtable.getplaneinfo = st7796_getplaneinfo;
+ priv->vtable.updatearea = st7796_updatearea;
+ priv->vtable.ioctl = st7796_ioctl;
+ priv->spi = spi;
+ priv->power = false;
+
+ /* Initialize display hardware */
+
+ st7796_init_display(priv);
+
+ priv->power = true;
+ lcdinfo("ST7796: Display ready\n");
+
+ return &priv->vtable;
+}
+
+/****************************************************************************
+ * Name: st7796_setrotation
+ *
+ * Description:
+ * Set display rotation at runtime. This function can be called directly
+ * by board code or applications that have access to the vtable pointer.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * rotation - Rotation angle in degrees (0, 90, 180, or 270)
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int st7796_setrotation(FAR struct fb_vtable_s *vtable, uint16_t rotation)
+{
+ return st7796_ioctl(vtable, FBIOSET_ROTATION, (unsigned long)rotation);
+}
+
+/****************************************************************************
+ * Name: st7796_getrotation
+ *
+ * Description:
+ * Get current display rotation.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ *
+ * Returned Value:
+ * Current rotation in degrees (0, 90, 180, or 270).
+ *
+ ****************************************************************************/
+
+uint16_t st7796_getrotation(FAR struct fb_vtable_s *vtable)
+{
+ FAR struct st7796_dev_s *priv = (FAR struct st7796_dev_s *)vtable;
+ return priv->rotation;
+}
diff --git a/include/nuttx/lcd/st7796.h b/include/nuttx/lcd/st7796.h
new file mode 100644
index 00000000000..8950cf2e2bb
--- /dev/null
+++ b/include/nuttx/lcd/st7796.h
@@ -0,0 +1,178 @@
+/****************************************************************************
+ * include/nuttx/lcd/st7796.h
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_LCD_ST7796_H
+#define __INCLUDE_NUTTX_LCD_ST7796_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Display raw dimensions (before orientation transform)
+ *
+ * These must be in the public header because board code needs them to
+ * calculate the effective xres/yres based on Kconfig orientation settings
+ * at compile-time. Without these, boards would need to hardcode dimensions.
+ */
+
+#define ST7796_XRES_RAW 320
+#define ST7796_YRES_RAW 480
+
+/* Default SPI frequency
+ *
+ * Must be in the public header because board code uses this as a safe
+ * default when the user hasn't specified a custom frequency via Kconfig.
+ * Centralizes the datasheet specification to prevent duplication.
+ */
+
+#define ST7796_SPI_MAXFREQUENCY 40000000
+
+/* Pre-defined MADCTL values for common orientations
+ *
+ * These must be in the public header because board code selects the
+ * appropriate MADCTL value based on hardware orientation and RGB/BGR
+ * panel type configured via Kconfig. This abstracts the internal MADCTL
+ * bit manipulation from board code. Values are absolute to eliminate
+ * dependency on internal bit definitions.
+ */
+
+#define ST7796_MADCTL_PORTRAIT 0x40
+#define ST7796_MADCTL_PORTRAIT_BGR 0x48
+#define ST7796_MADCTL_RPORTRAIT 0x80
+#define ST7796_MADCTL_RPORTRAIT_BGR 0x88
+#define ST7796_MADCTL_LANDSCAPE 0x20
+#define ST7796_MADCTL_LANDSCAPE_BGR 0x28
+#define ST7796_MADCTL_RLANDSCAPE 0xe0
+#define ST7796_MADCTL_RLANDSCAPE_BGR 0xe8
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+/* Board-specific configuration passed to driver at initialization.
+ *
+ * This structure must be in the public header because it defines the
+ * driver's configuration API. Board code instantiates and populates this
+ * structure to configure the driver without requiring board-specific
+ * Kconfig options in the generic driver.
+ */
+
+struct st7796_config_s
+{
+ uint32_t frequency; /* SPI clock frequency in Hz */
+ uint16_t xres; /* Horizontal resolution (after orientation) */
+ uint16_t yres; /* Vertical resolution (after orientation) */
+ uint16_t rotation; /* Initial rotation: 0, 90, 180, or 270 */
+ uint8_t bpp; /* Bits per pixel: 16 (RGB565) or 18 (RGB666) */
+ uint8_t madctl; /* Base MADCTL register value for orientation */
+};
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/****************************************************************************
+ * Name: st7796_fbinitialize
+ *
+ * Description:
+ * Initialize the ST7796 LCD controller as a framebuffer device.
+ *
+ * This function initializes the ST7796 display controller using the
+ * provided configuration and returns a framebuffer virtual table.
+ * The driver uses CONFIG_SPI_CMDDATA to control the DC (Data/Command)
+ * pin automatically via the SPI driver.
+ *
+ * Input Parameters:
+ * spi - SPI device instance configured for the ST7796
+ * config - Board-specific configuration (frequency, resolution, etc.)
+ *
+ * Returned Value:
+ * Pointer to framebuffer vtable on success; NULL on failure.
+ *
+ * Assumptions:
+ * - CONFIG_SPI_CMDDATA is enabled
+ * - DC pin has been registered with the SPI driver
+ * - CS pin has been registered with the SPI driver
+ * - RESET and backlight pins configured by board code
+ *
+ ****************************************************************************/
+
+FAR struct fb_vtable_s *st7796_fbinitialize(FAR struct spi_dev_s *spi,
+ FAR const struct st7796_config_s
+ *config);
+
+/****************************************************************************
+ * Name: st7796_setrotation
+ *
+ * Description:
+ * Set display rotation at runtime. Valid rotation values are 0, 90,
+ * 180, and 270 degrees. The rotation is applied by modifying the
+ * MADCTL register.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ * rotation - Rotation angle in degrees (0, 90, 180, or 270)
+ *
+ * Returned Value:
+ * OK on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int st7796_setrotation(FAR struct fb_vtable_s *vtable, uint16_t rotation);
+
+/****************************************************************************
+ * Name: st7796_getrotation
+ *
+ * Description:
+ * Get current display rotation.
+ *
+ * Input Parameters:
+ * vtable - Reference to the framebuffer virtual table
+ *
+ * Returned Value:
+ * Current rotation in degrees (0, 90, 180, or 270).
+ *
+ ****************************************************************************/
+
+uint16_t st7796_getrotation(FAR struct fb_vtable_s *vtable);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* __INCLUDE_NUTTX_LCD_ST7796_H */
diff --git a/include/nuttx/video/fb.h b/include/nuttx/video/fb.h
index ebd5f7f12ae..2c6f70a6691 100644
--- a/include/nuttx/video/fb.h
+++ b/include/nuttx/video/fb.h
@@ -313,6 +313,12 @@
#define FBIOSET_VSYNCOFFSET _FBIOC(0x001a) /* Set VSync offset in usec
* Argument: int */
+#define FBIOSET_ROTATION _FBIOC(0x001e) /* Set display rotation
+ * Argument: int */
+
+#define FBIOGET_ROTATION _FBIOC(0x001f) /* Get display rotation
+ * Argument: int* */
+
/* Linux Support ************************************************************/
#define FBIOGET_VSCREENINFO _FBIOC(0x001b) /* Get video variable info */
