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How to use Inland/Generic 3.5" TFT with Raspberry Pi OS Bookworm

1. Edit /boot/firmware/config.txt. Add the following lines:

enable_uart=1
dtparam=spi=on
dtoverlay=piscreen,drm,speed=16000000

2. Open sudo raspi-config. Under Advanced Options→Wayland, click X11. Then click OK & Finish. Don't reboot the Pi.

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Touch Coordinate Calibration with libinput

1. The Mathematical Framework

Modern libinput uses an Affine Transformation Matrix. To map a raw touch coordinate $(x, y)$ to a normalized screen coordinate $(x', y')$, we use the following equation:

$$ \begin{bmatrix} x' \ y' \ 1 \end{bmatrix} = \begin{bmatrix} a & b & c \ d & e & f \ 0 & 0 & 1 \end{bmatrix} \begin{bmatrix} x \ y \ 1 \end{bmatrix} $$

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# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

# Use this example for digital pin control of an H-bridge driver
# like a DRV8833, TB6612 or L298N.

import time
import board
import digitalio
from adafruit_motor import stepper

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import RPi.GPIO as gpio
import time

gpio.setmode(gpio.BCM)

gpio.setwarnings(False)

# Pins
ain1 = 16
ain2 = 20

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# Import required modules
import time
import RPi.GPIO as GPIO

# Declare the GPIO settings
GPIO.setmode(GPIO.BOARD)

# set up GPIO pins
GPIO.setup(7, GPIO.OUT) # Connected to PWMA