TFT display pi 3.5 inch LCDShow (lesson)

From regional-training

overview

This is an assembly lesson where the user extends a raspberry pi desktop to include a display driver for a TFT display[1].

We are using a goodtft/LCDShow TFT screen PCB which uses the XPT2046 chip.

The PCB plugs into the GPIO port and provides a display and a resistive touch overlay using the GPIO header pins.

There are quite a few variants of this board, and some come with a fan mount.

requisites

  • you must have internet connectivity
  • you need a pi W, pi 3, pi 4, or pi400 with extension card.
  • you need a LCDShow compatible TFT display. It is hard to tell from an Internet purchase because some PCB are not well marked. There are several board that use the same main chip:

For the best value this lesson should be run using a raspbian Lite edition.

suppliers

hardware installation

The installation is as follows:

  • follow Lesson:install raspberry_pi_OS to place a lite image on an sdcard and from settings make sure:
    • to configure the pi for ssh
    • to configure for WiFi
  • if you forgot to configure for ssh then on the sdcard touch /boot/ssh.txt which will caused ssh to start on boot
touch /boot/ssh.txt
  • if you forgot to setup WiFi then edit /rootfs/etc/wpa_supplicant/wpa_supplicant.conf and add
network={
       ssid="sid"
       psk="password"
}
  • assemble your raspberry pi into the screen case with the four screws supplied
  • if the display board has a fan, use the supplied screws to mount the fan
  • attach the display PCB to the GPIO header making sure that you use the top-left most pins with nothing over-hanging.
  • insert the sdcard image
  • plug into the pi
    • a keyboard
    • a mouse
    • a HDMI monitor into port 1 next to the power socket
    • a network cable into eth0 socket
    • connect power via the USB-C socket

prepare the system

Turn the system on.

  • login to a command shell and type
sudo su -
  • update the apt sources
sudo apt update
  • upgrade the libraries
sudo apt upgrade

Configure ssh for remote access.

  • install ssh
sudo apt install ssh -y
  • initialize ssh and run it
sudo apt enable ssh
sudo apt start ssh

You will need git to obtain the TFT device installation scripts

  • obtain git
sudo apt install git -y
  • obtain the IP address for reference
ip add

Now you are ready to remote access. If you do not have remote access you will need to use a monitor as well as a keyboard, and later on a mouse.

TFT driver

The driver installation script has been designed to work with X11 pre-installed.

Lets obtain the script and do some inspection.

  • login on your pi
ssh -Y <name>@<ip-address>
or from the keyboard.
  • change to the root user to make everything easier and observe the directory
 sudo su -
 pwd
  • obtain the script from the manufacturer's website (the URL should have come in the TFT kit)
git clone https://github.com/goodtft/LCD-show.git
  • inspect what happened
ls
  • now just change the permission recursively (this is a short-cut hack to ensure bash/shell scripts are executable)
chmod -R 755 LCD-show
  • now lets inspect the files
cd LCD-show
ls -lrta

oot@raspberrypi:~/LCD-show# ls -lrta
total 644
drwx------ 3 root root   4096 Aug 17 01:01 ..
-rwxr-xr-x 1 root root   6520 Aug 17 01:01 README.md
-rwxr-xr-x 1 root root   4019 Aug 17 01:01 PyMouse-1.0.tar.gz
-rwxr-xr-x 1 root root   4367 Aug 17 01:01 NANO24-show
-rwxr-xr-x 1 root root    750 Aug 17 01:01 MPI5094-show
-rwxr-xr-x 1 root root   1836 Aug 17 01:01 MPI5001-show
-rwxr-xr-x 1 root root   3244 Aug 17 01:01 MPI4009-show
-rwxr-xr-x 1 root root   3242 Aug 17 01:01 MPI4008-show
-rwxr-xr-x 1 root root   1064 Aug 17 01:01 MPI3510-show
-rwxr-xr-x 1 root root   3436 Aug 17 01:01 MPI3508-show
-rwxr-xr-x 1 root root   1022 Aug 17 01:01 MPI3508_480_320-show
-rwxr-xr-x 1 root root   1751 Aug 17 01:01 Mouse_Key.py
-rwxr-xr-x 1 root root   4200 Aug 17 01:01 MIS35-show
-rwxr-xr-x 1 root root   4205 Aug 17 01:01 MHS40-show
-rwxr-xr-x 1 root root   4515 Aug 17 01:01 MHS40C-show
-rwxr-xr-x 1 root root   4175 Aug 17 01:01 MHS35-show
-rwxr-xr-x 1 root root   4366 Aug 17 01:01 MHS35B-show
-rwxr-xr-x 1 root root   4202 Aug 17 01:01 MHS32-show
-rwxr-xr-x 1 root root   1409 Aug 17 01:01 MHS24-show
-rwxr-xr-x 1 root root    855 Aug 17 01:01 LCD-hdmi
-rwxr-xr-x 1 root root   1797 Aug 17 01:01 LCD7S-show
-rwxr-xr-x 1 root root   1797 Aug 17 01:01 LCD7H-show
-rwxr-xr-x 1 root root   1736 Aug 17 01:01 LCD7C-show
-rwxr-xr-x 1 root root   1732 Aug 17 01:01 LCD7B-show
-rwxr-xr-x 1 root root   3467 Aug 17 01:01 LCD5-show
-rwxr-xr-x 1 root root   1808 Aug 17 01:01 LCD55-show
-rwxr-xr-x 1 root root   4194 Aug 17 01:01 LCD35-show
-rwxr-xr-x 1 root root   4200 Aug 17 01:01 LCD32-show
-rwxr-xr-x 1 root root   4200 Aug 17 01:01 LCD28-show
-rwxr-xr-x 1 root root   4200 Aug 17 01:01 LCD24-show
-rwxr-xr-x 1 root root   4197 Aug 17 01:01 LCD24-3A+-show
-rwxr-xr-x 1 root root   4768 Aug 17 01:01 LCD154-show
-rwxr-xr-x 1 root root   1738 Aug 17 01:01 LCD101Y-show
-rwxr-xr-x 1 root root   1843 Aug 17 01:01 LCD101TMP-show
-rwxr-xr-x 1 root root   1837 Aug 17 01:01 LCD101H-show
-rwxr-xr-x 1 root root   1222 Aug 17 01:01 DPI7_1024_600-show
-rwxr-xr-x 1 root root   1222 Aug 17 01:01 DPI5_7_800_480-show
-rwxr-xr-x 1 root root   3215 Aug 17 01:01 system_restore.sh
-rwxr-xr-x 1 root root    708 Aug 17 01:01 system_config.sh
-rwxr-xr-x 1 root root   3103 Aug 17 01:01 system_backup.sh
-rwxr-xr-x 1 root root   6374 Aug 17 01:01 rotate.sh
-rwxr-xr-x 1 root root 119448 Aug 17 01:01 python-xlib_0.23-2_all.deb
drwxr-xr-x 3 root root   4096 Aug 17 01:01 etc
drwxr-xr-x 2 root root   4096 Aug 17 01:01 boot
-rwxr-xr-x 1 root root 117184 Aug 17 01:01 xserver-xorg-input-evdev_1%3a2.10.6-1+b1_armhf.deb
-rwxr-xr-x 1 root root  41542 Aug 17 01:01 xinput-calibrator_0.7.5-1_armhf.deb
drwxr-xr-x 4 root root   4096 Aug 17 01:01 usr
-rwxr-xr-x 1 root root 119392 Aug 17 01:01 xserver-xorg-input-evdev_1%3a2.10.6-2_arm64.deb
drwxr-xr-x 8 root root   4096 Aug 17 01:01 .git
drwxr-xr-x 6 root root   4096 Aug 17 01:01 .
  • lets look at system_backup.sh
oot@raspberrypi:~/LCD-show# cat system_backup.sh 
#!/bin/bash
if [ ! -d "./.system_backup" ]; then
sudo mkdir ./.system_backup
fi

sudo rm -rf ./.system_backup/*

if [ -f /etc/X11/xorg.conf.d/99-calibration.conf ]; then
sudo cp -rf /etc/X11/xorg.conf.d/99-calibration.conf ./.system_backup
sudo rm -rf /etc/X11/xorg.conf.d/99-calibration.conf
fi

if [ -f /etc/X11/xorg.conf.d/40-libinput.conf ]; then
sudo cp -rf /etc/X11/xorg.conf.d/40-libinput.conf ./.system_backup
sudo rm -rf /etc/X11/xorg.conf.d/40-libinput.conf
fi

if [ -d /etc/X11/xorg.conf.d ]; then
sudo mkdir -p ./.system_backup/xorg.conf.d
sudo rm -rf /etc/X11/xorg.conf.d
fi

result=`grep -rn "^dtoverlay=" /boot/config.txt | grep ":rotate=" | tail -n 1`
if [ $? -eq 0 ]; then
str=`echo -n $result | awk -F: '{printf $2}' | awk -F= '{printf $NF}'`
if [ -f /boot/overlays/$str-overlay.dtb ]; then
sudo cp -rf /boot/overlays/$str-overlay.dtb ./.system_backup
sudo rm -rf /boot/overlays/$str-overlay.dtb
fi
if [ -f /boot/overlays/$str.dtbo ]; then
sudo cp -rf /boot/overlays/$str.dtbo ./.system_backup
sudo rm -rf /boot/overlays/$str.dtbo
fi
fi

root_dev=`grep -oPr "root=[^\s]*" /boot/cmdline.txt | awk -F= '{printf $NF}'`
sudo cp -rf /boot/config.txt ./.system_backup
sudo cp -rf /boot/cmdline.txt ./.system_backup/
if test "$root_dev" = "/dev/mmcblk0p7";then
sudo cp -rf ./boot/config-noobs-nomal.txt /boot/config.txt
#sudo cp -rf ./usr/cmdline.txt-noobs-original /boot/cmdline.txt
else
sudo cp -rf ./boot/config-nomal.txt /boot/config.txt
#sudo cp -rf ./usr/cmdline.txt-original /boot/cmdline.txt
fi
if [ -f /usr/share/X11/xorg.conf.d/99-fbturbo.conf ]; then
sudo cp -rf /usr/share/X11/xorg.conf.d/99-fbturbo.conf ./.system_backup/
fi
sudo cp -rf ./usr/99-fbturbo.conf-original /usr/share/X11/xorg.conf.d/99-fbturbo.conf
sudo cp -rf /etc/rc.local ./.system_backup/
sudo cp -rf ./etc/rc.local-original /etc/rc.local

sudo cp -rf /etc/modules ./.system_backup/
sudo cp -rf ./etc/modules-original /etc/modules

if [ -f /etc/modprobe.d/fbtft.conf ]; then
sudo cp -rf /etc/modprobe.d/fbtft.conf ./.system_backup
sudo rm -rf /etc/modprobe.d/fbtft.conf
fi

if [ -f /etc/inittab ]; then
sudo cp -rf /etc/inittab ./.system_backup
sudo rm -rf /etc/inittab
fi

type fbcp > /dev/null 2>&1
if [ $? -eq 0 ]; then
sudo touch ./.system_backup/have_fbcp
sudo rm -rf /usr/local/bin/fbcp
fi

#type cmake > /dev/null 2>&1
#if [ $? -eq 0 ]; then
#sudo touch ./.system_backup/have_cmake
#sudo apt-get purge cmake -y 2> error_output.txt
#result=`cat ./error_output.txt`
#echo -e "\033[31m$result\033[0m"
#fi

if [ -f /usr/share/X11/xorg.conf.d/10-evdev.conf ]; then
sudo cp -rf /usr/share/X11/xorg.conf.d/10-evdev.conf ./.system_backup
sudo dpkg -P xserver-xorg-input-evdev
#sudo apt-get purge xserver-xorg-input-evdev -y  2> error_output.txt
#result=`cat ./error_output.txt`
#echo -e "\033[31m$result\033[0m"
fi

if [ -f /usr/share/X11/xorg.conf.d/45-evdev.conf ]; then
sudo cp -rf /usr/share/X11/xorg.conf.d/45-evdev.conf ./.system_backup
sudo rm -rf /usr/share/X11/xorg.conf.d/45-evdev.conf
fi

if [ -f ./.have_installed ]; then
sudo cp -rf ./.have_installed ./.system_backup
sudo rm -rf ./.have_installed
fi
  • the above script has an error, it is trying to copy a file to /usr/share/X11/xorg.conf.d; see if you can find it and write a test to prevent it when /usr/share/X11/xorg.conf.d does not exist.
  • save a copy of the file
 cp system_backup.sh system_backup.sh.1
  • prevent copy to non-existant directory
# RBH
if [ -f /usr/share/X11/xorg.conf.d ]; then
sudo cp -rf ./usr/99-fbturbo.conf-original /usr/share/X11/xorg.conf.d/99-fbturbo.conf
fi
sudo cp -rf /etc/rc.local ./.system_backup/
sudo cp -rf ./etc/rc.local-original /etc/rc.local
  • now execute it
./system_backup.sh
  • change to the backup directory
cd .system_backup
  • inspect what the script did
root@raspberrypi:~/LCD-show/.system_backup# ls -lrta
total 24
drwxr-xr-x 7 root root 4096 Aug 17 01:17 ..
-rwxr-xr-x 1 root root 1785 Aug 17 01:17 config.txt
-rwxr-xr-x 1 root root  103 Aug 17 01:17 cmdline.txt
-rwxr-xr-x 1 root root  420 Aug 17 01:17 rc.local
-rw-r--r-- 1 root root  203 Aug 17 01:17 modules
drwxr-xr-x 2 root root 4096 Aug 17 01:17 .
  • examine the files and the modules directory

Now we will examine the other scripts.

  • go back to the installation directory
cd /root/LCD-show    // or cd ..
  • find the scripts
ls -lrta *.sh

root@raspberrypi:~/LCD-show# ls -lrta *.sh
-rwxr-xr-x 1 root root 3215 Aug 17 01:01 system_restore.sh
-rwxr-xr-x 1 root root  708 Aug 17 01:01 system_config.sh
-rwxr-xr-x 1 root root 6374 Aug 17 01:01 rotate.sh
-rwxr-xr-x 1 root root 3155 Aug 17 01:10 system_backup.sh
  • examine the system_restore.sh
  • now run it and not what happens
./system_restore.sh

driver installation

🚩Note: We are going to trial install the TFT driver without an X11 desktop!

  • remote login / login to your pi and try to install the driver
sudo su -
cd LCD-show

🚩Note: Control-C interrupt it as soon as you see an error.

  • execute the installation script and get ready with the Control-C
 ./LCD35-show
  • See if you can fix the error listed below (by editing the LCD35-show file):
cp: cannot create regular file '/usr/share/X11/xorg.conf.d/99-fbturbo.conf': No such file or directory
  • put a test in the script to create /usr/share/X11/xorg.conf.d if it does not exist
  • re-run the script to its conclusion answering y to the apt installation question. Watch your screen closely!
cd LCD-show
./LCD35-show

Your raspberry pi should now reboot. (I recorded a movie here File:Tft-boot.mov).

TA screen-shot:

first boot after driver overlay
first boot after driver overlay

advanced

Recall that the LCD-Show installation scripts assumed that there was an X11 system installed and was relying on some directories. We modified those scripts so we could run them without error.

You could choose to restore the system with the system_restore.sh script.

  1. What happens if you restore the system?
  2. What happened to your external HDMI display?

uninstall

The installation may be reverted.

  • execute
cd LCD-Show
sudo ./system_restore.sh
  • then you should delete the directory so you can start again

desktop installation

🚩 Recall that the LCD-Show installation scripts assumed that there is an X11 system and we modified the scripts above to remove the errors, and then we tested the scripts.

This section will walk you through the installation of an LXDE desktop from a Lite installation.

🚩 Note: If you have used a desktop image on your sdcard you may skip this section.

We are going to load the LXDE desktop, because it is very light-weight.

We are also going to ensure that ssh is enabled so you will be able to remote from another computer so you can use cut-and-paste from the command-line.

🚩 If you do not have a remote terminal you will need to login with a keyboard and mouse and read your TFT screen and type instead.

LXDE

This desktop is pretty light weight. Install as follows:

  • switch to root
sudo su -
  • install X components
apt install xinit -y
apt install xinit -y
apt install lxde-core -y
apt install lxterminal -y
apt install lxappearance -y
  • now install a display manager
apt install lightdm
  • Now install local AU utf8 and region

Now re-install the TFT display again because we now have all our Xorg dependencies 

cd /root/LCD-show
./LCD35-show

Try starting X; this may not work as I have trouble with the display. I then tried installing 

apt install xserver-xorg-video-fbturbo
* drop back to your own shell
 Control-D
  • startx
startx

If that fails to start, then removed the fbturbo 

apt purge xserver-xorg-video-fbturbo

Then startX again 

statx

Problems will be logged to 

/var/log/Xorg.0.log

See if you can work out what is going wrong.

result

calibration

The touch screen may require calibration[2].

  • install the calibrator
cd /boot
cd LCD-show
sudo dpkg -i -B xinput-calibrator_0.7.5-1_armhf.deb
  • modify the calibration data with that shown by the application
sudo vi /etc/X11/xorg.conf.d/99-calibration.conf

Only resistive touch screens need to be calibrated, and not the capacitive touch screens.

rotation

The screen can be rotated around the major axes in increments of 90 degrees. (I have not expanded how to do so yet. See the reference for instructions.)

screen

These notes will be adapted[3]TBA write the screen rotation notes here.

resistive touch

TBA write the resistive touch rotation notes here.

references

  1. ↑ LCD Wiki http://www.lcdwiki.com/3.5inch_RPi_Display
  2. ↑ claibration https://github.com/goodtft/LCD-show/wiki/How-to-calibrate-the-touch-screen/cf471168de560df91b41ede41d6440ecb6ef4bc1
  3. ↑ display direction http://www.lcdwiki.com/res/Show_Direction_and_Touch/How_to_change_display_direction-GPIO-Resistive_Touch-V1.2.pdf

Need to include lesson plan layout.

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