Convert a basic calculator into a fully fledged Linux device
Add dtoverlay=calculator-keyboard to /boot/config.txt
Run autodts.sh and reboot the computer.
Create file /etc/modprobe.d/fbtft.conf and add this
options fbtft_device name=fb_ili9325 custom rotate=90 bgr=1 width=240 height=320 gpios=reset:7,dc:0,wr:1,cs:8,db00:17,db01:18,db02:21,db03:22,db04:23,db05:24,db06:25,db07:4,led:12
Add to /etc/modules: fbtft_device
Add to /boot/cmdline.txt fbcon=map:10 fbcon=font:VGA8x8
Change /usr/share/X11/xorg.conf.d/99-fbturbo.conf /dev/fb0 to /dev/fb1
For seeing key presses sudo showkey -s
To open on screen keyboard sudo matchbox-keyboard
Turn on number pad mouse control setxkbmap -option keypad:pointerkeys and then CTRL + SHIFT + NUMLOCK