EBC Exercise 12a 2.4 TFT LCD display via SPI

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thumb‎ Embedded Linux Class by Mark A. Yoder

2.4" TFT LCD

This is an exercise in interfacing the 2.4" TFT LCD display (ili9341) via a SPI bus. The newer using the tinyDRM driver and the older uses fbtft.

The Hardware

This table shows how to wire the LCD display for SPI 0.

LCD Bone
MISO P9_21
LED P9_16
SCK P9_22
MOSI P9_18
D/C P9_19
CS P9_17
GND P9_2
VCC P9_4


Clone the course repo.

bone$ git clone https://github.com/MarkAYoder/BeagleBoard-exercises.git exercises

and then

bone$ cd exercises/display/ili9341/fb
bone$ git pull
bone$ ./on.sh

After a moment the display should turn dark. Look in on.sh to see what it did. If the display doesn't turn on, look in on.sh and make sure it's set for the correct SPI bus.

Using the framebuffer

Displaying Images

Follow the instructions in install.sh to download fbi and some images.

bone$ sudo apt update
bone$ sudo apt install fbi

Display them with:

bone$ sudo fbi -noverbose -T 1 -a boris.png

You should now see Boris the Beagle on your display.

Playing Movies

Install mplayer and load a movie on the Bone (see install.sh).

bone$ sudo apt install mplayer

Get something to play

bone$ wget http://hubblesource.stsci.edu/sources/video/clips/details/images/hst_1.mpg

And play it

bone$ export SDL_VIDEODRIVER=fbcon 
bone$ export SDL_FBDEV=/dev/fb0

bone$ mplayer -vf-add rotate=4 -framedrop hst_1.mpg

Play the movie. Rotate the movie.

Generate Text

Install imagemagick.

bone$ sudo apt install imagemagick

See text.sh for an example of using imagemagick to write text to the LCD display. Write your name on the LCD. Display an image and write some text on it.

# Here's how to use imagemagick to display text
# Make a blank image

# From: http://www.imagemagick.org/Usage/text/
convert -background lightblue -fill blue -font Times-Roman -pointsize 24 \
     -size $SIZE \
     label:'ImageMagick\nExamples\nby Anthony' \
     -draw "text 0,200 'Bottom of Display'" \

sudo fbi -noverbose -T 1 $TMP_FILE


It's not hard to get pygame to display on the LCD.

bone$ sudo apt install pygame
bone$ sudo pip3 install requests pillow
bone$ cd exercises/displays/ili9341/fb/pygame
bone$ sudo ./clock.py

Look in clock.py to see how to direct the graphics to the LCD.


The tinyDRM driver requires a 4.19 kernel or newer. Run uname -a to see which kernel is being run. If it isn't new enough run:

bone$ cd /opt/scripts/tools
bone$ sudo ./update_kernel.sh --lts-4_19
bone$ reboot

Clone the course repo.

bone$ git clone https://github.com/MarkAYoder/BeagleBoard-exercises.git exercises

and then

bone$ cd exercises/display/ili9341
bone$ git pull
bone$ cd tinyDRM
bone$ ls
BB-LCD-ADAFRUIT-24-SPI1-00A0.dts  install.sh  Makefile

BB-LCD-ADAFRUIT-24-SPI1-00A0.dts is the device driver for the LCD attached to SPI 1.

To compile it:

bone$ make
cpp -x assembler-with-cpp -nostdinc -I /opt/source/dtb-4.19-ti/include -undef -D__DTS__ < BB-LCD-ADAFRUIT-24-SPI1-00A0.dts | dtc -i /opt/source/dtb-4.19-ti/include -I dts -O dtb -b 0 -o BB-LCD-ADAFRUIT-24-SPI1-00A0.dtbo -
BB-LCD-ADAFRUIT-24-SPI1-00A0.dtbo: Warning (chosen_node_is_root): /fragment@0/__overlay__/chosen: chosen node must be at root node
bone$ make install
sudo cp --backup BB-LCD-ADAFRUIT-24-SPI1-00A0.dtbo /lib/firmware
Add uboot_overlay_addr4=/lib/firmware/BB-LCD-ADAFRUIT-24-SPI1-00A0.dtbo to /boot/uEnv.txt

Now, follow the instructions from the Makefile and edit /boot/uEnv.txt and find the line starting with


Uncomment it and change it to:


Then reboot and check of /dev/fb0

bone$ sudo reboot

After rebooting...

bone$ ls -ls /dev/fb0
0 crw-rw---- 1 root video 29, 0 Oct  3 10:07 /dev/fb0

You can control the backlight with:

bone$ cd /sys/devices/platform/backlight_pwm/backlight/backlight_pwm
bone$ sudo chgrp debian *                         
bone$ sudo chmod g+w *

Turn the display off, then on with:

bone$ echo 1 > bl_power                        
bone$ echo 0 > bl_power

Change the brightness to 25% with:

bone$ echo 25 > brightness

Now jump to the Using the Frame Buffer section to see how to display images, etc..

thumb‎ Embedded Linux Class by Mark A. Yoder