Touch LCD Shield¶

The Touch LCD Shield gives the OpenMV Cam a 2.3 inch 320x240 capacitive multi-touch display so you can preview the camera output (and accept input) without a host computer. Two Qwiic headers make it easy to chain extra I2C devices.

For full datasheet, photos, and ordering see the Touch LCD Shield product page.

Highlights¶

2.3 inch TFT LCD, 320x240, 16-bit RGB565
Capacitive multi-touch input
PWM-controllable backlight
Two Qwiic connectors for easy I2C device chaining

Pinout¶

Pin reference¶

Pin	Function
P0	LCD MOSI (SPI data to display)
P1	LCD TE (tearing-effect output)
P2	LCD SCLK (SPI clock)
P3	LCD SSEL (SPI chip select)
P4	Touch / Qwiic SCL (I²C clock — shared with Qwiic headers)
P5	Touch / Qwiic SDA (I²C data — shared with Qwiic headers)
P6	LCD backlight
P7	Touch / LCD RESET_N
P8	LCD RS (data / command select)
P9	Touch INT_N
3.3V rail	Powers the LCD and touch controllers
GND rail	Common ground

Usage¶

Drive the shield through the display.SPIDisplay class. Stream camera frames to the 320×240 LCD:

import csi
import display
import image
import time

csi0 = csi.CSI()
csi0.reset()
csi0.pixformat(csi.RGB565)
csi0.framesize(csi.QVGA)

lcd = display.SPIDisplay(width=320, height=240, bgr=True)
clock = time.clock()

while True:
    clock.tick()
    lcd.write(csi0.snapshot(), hint=image.CENTER | image.SCALE_ASPECT_KEEP)
    print(clock.fps())

Drive the backlight via PWM for adjustable brightness. Wrap machine.PWM in a small backlight controller class and pass it to SPIDisplay through its backlight argument — SPIDisplay calls backlight(value) on the object whenever it needs to update the level:

import display
from machine import Pin, PWM


class PWMBacklight:
    """Drives a backlight pin with machine.PWM (0–100 %)."""

    def __init__(self, pin, frequency=200):
        self._pwm = PWM(Pin(pin), freq=frequency, duty_u16=0)

    def backlight(self, value):
        self._pwm.duty_u16(int(value * 65535 / 100))

    def deinit(self):
        self._pwm.deinit()


lcd = display.SPIDisplay(width=320, height=240, bgr=True,
                         backlight=PWMBacklight("P6"))
lcd.backlight(50)  # 0–100

The on-board GT911 capacitive controller is wired to the camera’s I²C bus on P4/P5, with reset on P7 and interrupt on P9. Read multi-touch data through the gt911.GT911 class:

from machine import I2C, Pin
import gt911
import time

bus = I2C(scl=Pin("P4"), sda=Pin("P5"), freq=400_000)
touch = gt911.GT911(bus, reset_pin="P7", irq_pin="P9",
                    width=320, height=240, touch_points=5)

while True:
    n, points = touch.read_points()
    for i in range(n):
        x, y, size, tid = points[i]
        print("touch", tid, "->", x, y)
    time.sleep_ms(20)

Warning

This page is under construction.