Raspberry PI touchscreen
I got a nice case with an embedded 3.5" touchscreen from a chinese supplier, it comes even with a small pen for only a few euros and no shipping, it is incredible. The Display is run from the GPIO pins and has the XPT20It works with jessie more or less out of the box. I wanted to use it in portrait mode and that was a little more complex. So with some Google Fu and trial and error I got it to work with X.
This is what I did:
```shell
# to rotate the display 90 is the default landscape
pi@raspifi:~ $ DISPLAY=:0 xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ ADS7846 Touchscreen id=6 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ CHICONY HP Basic USB Keyboard id=7 [slave keyboard (3)]
pi@raspifi:~ $ sudo su -
root@raspifi:~ # cat /boot/config.txt
root@raspifi:~ # vi /boot/config.txt
root@raspifi:~ # cat /boot/config.txt
<snip>
dtoverlay=tft35a:rotate=180
<snip>
root@raspifi # reboot
# and it will come up with a rotated screen (portrait mode)
# to rotate the touchscreen after the reboot
pi@raspifi $ DISPLAY=:0.0 xinput --set-prop 'ADS7846 Touchscreen' 'Coordinate Transformation Matrix' 0 -1 1 1 0 0 0 0 1in=200,ymax=39
```