2.8" SPI LCD

ILI9341 240×320 panel on an 18-pin FPC, with a transistor-switched backlight.

Panel: ILI9341 240×320
Bus: SPI, 6 GPIO
Connector: J5 · 18-pin FPC
Driver: LovyanGFX

The panel plugs into J5, an 18-way FPC connector on the back face. Six GPIO carry a standard 4-wire SPI link — clock, MOSI, MISO, chip-select — plus a data/command select and a reset.

The backlight is not driven directly. GPIO7 goes through R23 into the base of Q4, an SS8050 NPN that sinks the four backlight LED cathodes on J5 pins 5–8. R21 pulls the base down so the backlight stays off until firmware asserts it. Because it is a transistor rather than a constant-current driver, PWM on GPIO7 is what gives you brightness control.

J5 pins 1–4 are the resistive touch lines. They are unused on this build — the panel is driven write-only in practice, so even MISO is optional.

Pins

Pin	Net	Role	Function
GPIO7	LCDBL	BACKLIGHT	Backlight enable / PWM. Drives Q4 through 10K R23, 470K pulldown R21. HIGH = on.
GPIO11	LCDSCK	SPI CLK	SPI clock → J5 pin 16.
GPIO12	LCDCS	SPI CS	Chip-select, active LOW → J5 pin 14.
GPIO13	LCDDC	D/C	Data / command select → J5 pin 15.
GPIO14	LCDRST	RST	Panel reset, active LOW → J5 pin 17.
GPIO15	LCDMOSI	SPI MOSI	Data out, ESP32-S3 → LCD, J5 pin 13.
GPIO16	LCDMISO	SPI MISO	Data in from LCD, J5 pin 12. Not required write-only.

Parts

J5 18-pin FPC, 0.5 mm Panel connector — SPI, backlight cathodes, 3V3, GND
Q4 SS8050 NPN low-side switch for the backlight LEDs
R23 / R21 10K / 470K Base resistor and pulldown for Q4

Firmware

firmware/testkit/testkit.ino

constexpr int PIN_LCD_SCK  = 11;
constexpr int PIN_LCD_CS   = 12;
constexpr int PIN_LCD_DC   = 13;
constexpr int PIN_LCD_RST  = 14;
constexpr int PIN_LCD_MOSI = 15;
constexpr int PIN_LCD_MISO = 16;
constexpr int PIN_LCD_BL   = 7;

constexpr uint8_t LCD_ROTATION   = 1;
constexpr uint8_t LCD_BRIGHTNESS = 190;

Notes

The touch panel is not documented or populated on this revision — J5 pins 1–4 (Y−/X−/Y+/X+) go nowhere useful.