Raspberry Pi Project

Installing And Using A TFT Touch Screen On A Raspberry Pi

To add onto the already neat raspberry pi I purchased a 2.8" 320x240 touch screen. The screen works out to be roughtly the same size of the PI which makes installation and making a case for it easy. It also does not require any external power and can be powered directly off the PI's internal power system. The particular screen I used is the Adafruit 1601. I used the instructions from the adafruit website, but below are the instructions I followed to get the screen up and running.

Physical Assembly

To get to use the screen you have to get some soldering done and assemble the pins onto the screen's circuit board. It isnt as hard as it seems follow the included paper leaflet and take your time and make sure you dont solder across the pins. Once soldered turn off the PI and simply place and insert the touchscreen onto pi. Turn the pi back on and boot into the OS as normal the raspberry pi.

Software Installation

With the hardware part behind us we now need to install the software so we can use the screen. First Click here to download all the software required and extract the files via the following:

tar zxvf raspberrypi-touchscreen.tar.gz

Before we install the files we want to update your PI:

sudo apt-get update

Now install the touch screen software:

sudo dpkg -i -B *.deb

Now reboot to let the above take affect:

sudo shutdown -r now

Software Drivers

Test the drivers by running the following. The screen will flicker on and off and then the last 2 commands will start X on the screen. It wont function as a touchscreen yet but you should get a desktop.

sudo modprobe spi-bcm2708 sudo modprobe fbtft_device name=adafruitts rotate=90 export FRAMEBUFFER=/dev/fb1 startx

Hit CTRL+C to cancel and go back to the console....now we will make the screen auto load on start up

Edit the modules file:

sudo nano /etc/modules

add the following lines to the file

spi-bcm2708 fbtft_device

Modify Modprobe:

sudo nano /etc/modprobe.d/adafruit.conf

add the following into that file:

options fbtft_device name=adafruitts rotate=90 frequency=32000000

Explanation:
The rotate= variable tells the driver to rotate the screen 0 90 180 or 270 degrees.
0 is portrait, with the bottom near the "Adafruit Logo"
90 is landscape, with the bottom of the screen near the buttons.
180 is portrait, with the top near the "Adafruit Logo"
270 is landscape, with the top of the screen near the buttons.

The frequency= variable tells the driver how to fast to drive the display. 32MHz (32000000) is a pretty nice 20 FPS rate but if your screen is acting funny, try taking it down to 16MHz (16000000)

Now reboot to make changes stick

sudo shutdown -r now

look at the console output (or run dmesg in the console window after logging in) you will see the modules install. Look in particular for the STMPE610 detection and the ILI9340 screen frequency. Once rebooted log in and we can finish the rest of the setup.

The following will let the touchscreen work in landscape mode (your display and touchscreen have to be the same):

sudo mkdir /etc/X11/xorg.conf.d sudo nano /etc/X11/xorg.conf.d/99-calibration.conf

In this new file enter the following

Section "InputClass" Identifier "calibration" MatchProduct "stmpe-ts" Option "Calibration" "3800 200 200 3800" Option "SwapAxes" "1" EndSection

Now try X windows again...

FRAMEBUFFER=/dev/fb1 startx

If all goes well X should start again....hit CTRL+C to get back to the console

If you dont want to have to keep typing "FRAMEBUFFER=/dev/fb1" every time you want to start X you can put it in your profile so it does it automatically for you.

sudo nano ~/.profile

And add the following under the line that starts with "#mask..."

export FRAMEBUFFER=/dev/fb1

Calibrate Touchscreen

Although I found mind pretty spot on every touch screen should be calibrated to make sure your touch is precisely measured.

sudo nano /etc/udev/rules.d/95-stmpe.rules

In this new file enter the following:

SUBSYSTEM=="input", ATTRS{name}=="stmpe-ts", ENV{DEVNAME}=="*event*", SYMLINK+="input/touchscreen"

Remove and re-install the touchscreen with

sudo rmmod stmpe_ts; sudo modprobe stmpe_ts ls -l /dev/input/touchscreen

The touchscreen file should point to eventX where X is some number, that number will be different on different setups depending whats plugged into what slot

Install the calibrate software

sudo apt-get install evtest tslib libts-bin

After running the following touch the screen in several areas. You should get various output of where you have placed your finger:

sudo evtest /dev/input/touchscreen

Now finally run the follwing and run through the prompts to calibrate your screen. Ideally use a stylus but a finger will do.

sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/touchscreen ts_calibrate

Test the drawing ability of the screen via:

sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/touchscreen ts_test

Playing Video

Ideally the video should be sized to 320x240, this will save a lot of cpu time and resouces. But run the following and replace the FILE.MP4 with your movie file. If you dont have mplayer installed run "sudo apt-get install mplayer" first.

mplayer -vo fbdev2: /dev/fb1 -x 240 -y 320 -framedrop FILE.MP4

Displaying Images

You can display images directly from the console but first you need the software to do so

sudo apt-get install fbi

Now run the following replaceing MYFILE.JPG with your file

sudo fbi -T 2 -d /dev/fb1 -noverbose -a MYFILE.JPG

Controlling The Backlight

Either to save some voltage or just to save wear and tear on the screen LED you can turn on and off the light that drives the screen. First we set up access to the lighting which turns off the light as well.

sudo sh -c "echo 252 > /sys/class/gpio /export" sudo sh -c "echo 'out' > /sys/class/gpio/gpio252/direction"

To turn on the screen

sudo sh -c "echo '1' > /sys/class/gpio/gpio252/value"

To turn off the screen

sudo sh -c "echo '0' > /sys/class/gpio/gpio252/value"