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doc/esp32s3: Update esp32s3-touch-lcd7 documentation

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This commit updates the board documentation.

Signed-off-by: Alan C. Assis <acassis@gmail.com>
Assisted-by: Claude Code
This commit is contained in:
Alan Carvalho de Assis 2026-08-23 12:53:19 -03:00 • committed by Alin Jerpelea
parent 5486ed1e9b
commit 1267f78dcc
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Documentation/platforms/xtensa/esp32s3/boards/esp32s3-touch-lcd7/index.rst
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@ -78,6 +78,42 @@ The board has a 7-inch LCD:
EXIO2 DISP Backlight enable pin
========= ======== =========================
The panel is an EK9716 driven over a 16-bit parallel RGB565 bus by the
LCD_CAM peripheral. Its timing is:
==================== =======
Parameter Value
==================== =======
Resolution 800x480
Pixel clock 16 MHz
HSYNC pulse width 4
HSYNC back porch 8
HSYNC front porch 8
VSYNC pulse width 4
VSYNC back porch 8
VSYNC front porch 8
==================== =======
The RGB bus takes most of the usable pins, so the panel reset and the
display enable are not wired to GPIOs. They hang off a CH422G I/O
expander, reached over the I2C bus shared with the touch controller:
========= ============ ==================================
Signal Connection Description
========= ============ ==================================
SDA GPIO8 I2C data, expander and touch
SCL GPIO9 I2C clock, expander and touch
TP_RST CH422G EXIO1 GT911 touch controller reset
DISP CH422G EXIO2 Display and backlight enable
LCD_RST CH422G EXIO3 Panel reset
SD_CS CH422G EXIO4 TF card chip select
USB_SEL CH422G EXIO5 USB / CAN transceiver select
========= ============ ==================================
A 800x480 RGB565 framebuffer is 768000 bytes and does not fit in internal
RAM, so any configuration that drives the panel must also enable the
onboard 8MB octal PSRAM and leave it in the common heap.
Configurations
==============
@ -92,6 +128,50 @@ All of the configurations presented below can be tested by running the following
Configuration Directories
-------------------------
lcd
---
Brings up the onboard 7 inch 800x480 panel as a framebuffer character
driver at ``/dev/fb0``, on top of the ``usbnsh`` console. The CH422G I/O
expander is used to take the panel out of reset and to switch the display
on once the framebuffer exists, and the PSRAM the framebuffer is allocated
from is enabled.
Note that the console is on UART0, GPIO43 and GPIO44, reached through the
USB-to-UART bridge on the UART USB-C connector. It is deliberately not on
the native USB peripheral, because that is the connector a USB host
configuration drives.
``apps/examples/fb`` is included to prove the panel out. It reports the
geometry of the framebuffer it found and then draws a series of nested
rectangles over the whole display::
nsh> fb
VideoInfo:
fmt: 11
xres: 800
yres: 480
nplanes: 1
PlaneInfo (plane 0):
fbmem: 0x3c050040
fblen: 1536000
stride: 1600
display: 0
bpp: 16
Mapped FB: 0x3c050040
Use consecutive fbmem2 = 0x3c10b840, yoffset = 480
0: ( 0, 0) (800,480)
1: ( 72, 43) (656,394)
2: (144, 86) (512,308)
3: (216,129) (368,222)
4: (288,172) (224,136)
5: (360,215) ( 80, 50)
Test finished
The framebuffer is in PSRAM, which is why ``fbmem`` is in the 0x3c000000
range, and ``fblen`` is 1536000 rather than 768000 because the driver is
double buffered by default.
usbnsh
------