Hey guys, I've spent the last couple of weeks trying to get a TFT display with touch screen to work on my Orange Pi PC board, and I've decided to share my step-by-step solution here. This tutorial is heavily based on Guide: How to use Touchscreen + LCD on H3 devices by Kutysam, but I had to do some extra steps for it to work properly. This tutorial is only for Mainline kernel, I was able to get the graphical screen working with Kutysam's guide for Legacy, but couldn't make the touch work.
First of all this is the display I'm using: LCD module Pi TFT 3.5 inch (320*480) Touchscreen Display Module TFT for Raspberry Pi 3. I believe it is a clone of this Waveshare screen.
Also, I am using the image Armbian_5.38_Orangepipc_Debian_stretch_next_4.14.14_desktop, but it should work for the headless version (server) too, if you install a display manager, desktop environment and the X server.
All the commands below are assumed to be run as root user. If you're not root, add "sudo" to the beginning of each command.
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Preparation
First of all make sure you have the latest package updates by running
apt-get update && apt-get upgrade
This might take a while. If the packages have been installed successfully, reboot. On a fresh install I was getting the following error message:
If that happens to you, just run the command again and it should download everything properly. If it still isn't working you could try cleaning the apt cache.
After that, install these Make prerequisites:
apt-get install build-essentials
For some reason the linux-headers package for sunxi is not included in the repository, this thread might explain it better than me. Either way, download and install the package with dpkg:
wget http://apt.armbian.com/pool/main/l/linux-4.14.18-sunxi/linux-headers-next-sunxi_5.41_armhf.deb
dpkg -i linux-headers-next-sunxi_5.41_armhf.deb
Now we need to edit armbianEnv.txt to enable the overlays for spi and cs1
nano /boot/armbianEnv.txt
Add the following lines to the end of the file (Be careful with spaces in the end of the lines... I lost a couple of days trying to figure out what the problem was when I had an extra space after "param_spidev_spi_bus=0" )
overlays=spi-spidev spi-add-cs1
param_spidev_spi_bus=0
param_spidev_spi_cs=1
And reboot.
Screen
Now we need to configure fbtft and fbtft_device on boot. Note: I had to put "98" in the start of the filename, or else I'd get the following error: "fbtft_device: spi_busnum_to_master(0) returned NULL" in dmesg after I installed the touchscreen. I believe it has something to do with the load order, so if you're having problems with this file you could try changing the prefix to 99 or removing it.
nano /etc/modules-load.d/98-fbtft.conf
Insert the following on the file:
fbtft
fbtft_device
Now we have to load fbtft_device options on boot. Open the file with:
nano /etc/modprobe.d/fbtft.conf
Add the following:
options fbtft_device rotate=90 name=piscreen speed=16000000 gpios=reset:2,dc:71 txbuflen=32768 fps=25
And reboot. At this point your screen should at least turn black. For me, the GUI wouldn't load unless I typed 'startx' on the console. So this is how I fixed it to always display the GUI on boot:
apt-get install xserver-xorg-video-fbdev
nano /usr/share/X11/xorg.conf.d/99-fbdev.conf
Insert this in the file:
Section "Device"
Identifier "piscreen"
Driver "fbdev"
Option "fbdev" "/dev/fb0"
EndSection
At this point the screen should be displaying the Armbian GUI, with mouse and keyboard working, but without touch screen. Let's fix that.
Touch
First we need to download and compile the ads7846 driver (apparently it is compatible with xpt2046).
mkdir ds7846
cd ds7846
wget https://sourceforge.net/p/openipmi/linux-ipmi/ci/master/tree/drivers/input/touchscreen/ads7846.c?format=raw
mv ads7846.c?format=raw ads7846.c
nano Makefile
Insert the following on the makefile:
obj-m := ads7846.o
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
all:
$(MAKE) -C $(KDIR) M=$(PWD) modules
clean:
$(MAKE) -C $(KDIR) M=$(PWD) clean
install:
$(MAKE) -C $(KDIR) M=$(PWD) modules_install
Now let's compile and load the module into the kernel:
make
make install
depmod
Now we'll build and install the ads7846_device module from fbtft_tools:
cd ..
git clone https://github.com/notro/fbtft_tools/
cd fbtft_tools/ads7846_device
make
make install
depmod
Let's load ads7846 and ads7846_device on boot
sudo nano /etc/modules-load.d/99-ads7846.conf
After that let's load the options for ads7846_device. These configs worked best for me, but you can play with them and tweak if needed.
nano /etc/modprobe.d/ads7846_device.conf
Insert the following:
options ads7846_device model=7846 cs=1 gpio_pendown=1 keep_vref_on=1 swap_xy=1 pressure_max=255 x_plate_ohms=60 x_min=200 x_max=3900 y_min=200 y_max=3900
Reboot, and the touch should be working!
Well, for me not entirely. The Y axis seemed to be reversed, so here are the steps I took to configure it:
First of all, we need xinput to configure the touch screen options. Install it with this command:
apt-get install xinput
Now we need to set the "swap_xy" option to 0 in ads7846_device configuration file. Open it with:
nano /etc/modprobe.d/ads7846_device.conf
Replace its contents with this:
options ads7846_device model=7846 cs=0 gpio_pendown=1 keep_vref_on=1 swap_xy=0 pressure_max=255 x_plate_ohms=60 x_min=200 x_max=3900 y_min=200 y_max=3900
Reboot to apply the changes. Now we need to find out the touchscreen name on xinput. Run this command:
DISPLAY=:0.0 xinput list
You should get a list of pointer devices, and the touchscreen should be on it. In my case the name is 'ADS7846 Touchscreen'. At this point you might get an "unable to connect to X server error". If that's the case, you can add the required X permissions for your user with the command (taken from this ask ubuntu answer):
export XAUTHORITY=$(eval echo ~`who | grep tty7 | sed 's/\([a-z]*\).*/\1/'`)/.Xauthority
And "xinput list" should be working. Now we can try to configure it with xinput's "set-prop" parameter:
DISPLAY=:0.0 xinput --set-prop 'ADS7846 Touchscreen' 'Coordinate Transformation Matrix' 0 -1 1 1 0 0 0 0 1
Test your display to see if it works. This matrix worked best for me, but you might need to tweak it. Refer to this guide for more info on how coordinate transformation matrices work.
Now you need to run this command every time the session starts. To automate it, I added the command to the .xsessionrc file:
nano /home/{your username}/.xsessionrc
Append the xinput set-prop command:
DISPLAY=:0.0 xinput --set-prop 'ADS7846 Touchscreen' 'Coordinate Transformation Matrix' 0 -1 1 1 0 0 0 0 1
If you have multiple users logging in the session displayed on your screen, you might need to add this file for every user. ".xsessionrc" was the only file where I could get this working.
And that's it! Your display + touch screen should be working properly now!
I am still very newbie with Armbian and single board computers, and there is much I don't understand yet, so if you have any questions, comments or suggestions on this guide please post them below. See you all.
