Please consider that these instructions may not be the ideal solution depending on the needs of a given project. Adafruit’s forums are a valuable resource for help regarding their products.

These are the steps I used in order to run a fullscreen Python app on a Raspberry Pi with an Adafruit 2.8" resistive TFT display.

Raspberry Pi With an Adafruit TFT Display

Warning

For this process, I am using Raspbian Lite as the base image for my Pi and then installing an X11 environment. If you are not using Raspbian Lite then these steps may break your current configuration and you should be careful before proceeding.

These steps were tested on a “fresh” install of Rasbpian Lite and no other setup.

Required Software

Enable the nonfree Raspbian repository. The Adafruit script (which we’ll get to later and is required to support the display properly) requires this repo, and as of time of writing, this repo is not enabled by default. 

cat << EOF | sudo tee /etc/apt/sources.list.d/nonfree.list
deb http://mirrordirector.raspbian.org/raspbian/ stretch main contrib non-free rpi firmware
EOF

Install required packages for our fullscreen app.

sudo apt-get update && \
sudo apt-get install --no-install-recommends \
    sudo \
    cmake \
    xorg \
    openbox \
    lightdm \
    python3 \
    python3-tk \
    python3-rpi.gpio \
    xserver-xorg-legacy \
    xserver-xorg-video-fbdev

Modify the lightdm config script at /etc/lightdm/lightdm.conf to enable autologin if it is not already enabled. 

cat << EOF | sudo tee /etc/lightdm/lightdm.conf
[SeatDefaults]
autologin-user=pi
# Prevent the screen from shutting off automatically.
xserver-command=X -s 0 dpms
EOF

Run the Adafruit TFT install script as described on their site. 

cd ~ && \
wget https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/adafruit-pitft.sh && \
chmod +x adafruit-pitft.sh && \
sudo ./adafruit-pitft.sh

The script will ask a series of question. You should answer to the best of your ability. If you have a different screen than the 2.8" resistive version then you should answer accordingly.

When asked Would you like the console to appear on the PiTFT display? [y/n] I chose n since the goal here is to use a GUI on the TFT display and not just text.

When asked Would you like the HDMI display to mirror to the PiTFT display? [y/n] I chose y since that is a simple way to get GUI support on the TFT display according to Adafruit’s website.

Reboot the Pi when prompted. The device should log in as pi automatically using the openbox window manager. The Pi display should be blank after it boots, except for a mouse cursor.

App

Create the openbox config directory for the pi user if it does not exist. 

mkdir -p $HOME/.config/openbox

Create a script at $HOME/.config/openbox/autostart for the pi user. This script will be run at login. 

cat << EOF > $HOME/.config/openbox/autostart
# redirect all output to a log file
# -u so that output is flushed immediately to the log
python3 -u $HOME/app.py > $HOME/app.log 2>&1 &
EOF

The & at the end is required for every command in the autostart script.

Create a file $HOME/app.py for our python application code. 

import tkinter as tk

class FullScreenApp(object):
    padding=3
    dimensions="{0}x{1}+0+0"

    def __init__(self, master, **kwargs):
        self.master=master
        width=master.winfo_screenwidth()-self.padding
        height=master.winfo_screenheight()-self.padding
        master.geometry(self.dimensions.format(width, height))

        b = tk.Button(self.master, text="Press me!", command=lambda: self.pressed())
        b.place(relx=0.5, rely=0.5, anchor=tk.CENTER)

    def pressed(self):
        print("clicked!")

root=tk.Tk()
root.wm_attributes('-fullscreen','true')

app=FullScreenApp(root)

root.mainloop()

Reboot. The app should launch automatically in fullscreen mode.

Screen On / Off

You can use a script like this to enable or disable the LCD with the first two GPIO buttons tied to the TFT. 

#!/usr/bin/env python3

import RPi.GPIO as GPIO
import time
import os

GPIO.setmode(GPIO.BCM)

GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(22, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(27, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while True:
    # Screen on
    input_state = GPIO.input(17)
    if input_state == False:
        print('screen on', flush=True)
        print('1', file=open('/sys/class/backlight/soc:backlight/brightness', 'w'))
        time.sleep(0.2)

    # Screen off
    input_state = GPIO.input(22)
    if input_state == False:
        print('screen off', flush=True)
        print('0', file=open('/sys/class/backlight/soc:backlight/brightness', 'w'))
        time.sleep(0.2)

    # Screen off and power off
    input_state = GPIO.input(27)
    if input_state == False:
        print('screen off and power off', flush=True)
        print('0', file=open('/sys/class/backlight/soc:backlight/brightness', 'w'))
        os.system('shutdown -h now')
        time.sleep(3)

You could potentially have the script run at boot by appending the following to /etc/rc.local towards the end of the file before it calls the exit command. 

python3 -u /home/pi/buttons.py &

It seems there may be a few reasons the TFT/LCD will automatically shut off, and changing the brightness does nothing in that case. So those buttons and the accompanying script would be useless at that point.

The lightdm.conf above should disable the auto-off behavior of the TFT, but other methods may be required as well.

Notes on Adafruit PiTFT Support

As of time of writing, Adafruit offers an installation script that is designed to work with the latest standard/official Raspbian images. Adafruit previously offered custom Raspbian images with TFT support built in. Those images are now deprecated and the use of the script is encouraged.

Unless otherwise noted, or the process changes over time, one should use the installation script as instructed by Adafruit to enable a PiTFT with touch support!

Citations