eGalax touchscreens on Ubuntu

17 June 2022

eGalax resistive and capacitive touch controllers turn up in a lot of industrial and kiosk panels. On Ubuntu the panel is usually detected as a generic USB HID device and touches more or less work, but you do not get calibration or multi-touch behaving properly until you install the vendor's eGTouch driver. The catch is that the driver's installer does not set up a reliable start-at-boot, so you have to do that part yourself. This is on Ubuntu 18.04.

Install the driver

Download the current eGTouch driver for your architecture from eGalax, unpack it and run the installer:

tar xvzf eGTouch_v2.5.xxxx.L-x.tar.gz
cd eGTouch_v2.5.xxxx.L-x
sudo ./setup.sh

Confirm the controller is actually on the USB bus and being seen:

lsusb
sudo dmesg | grep -i touch

Make it start at boot

The installer puts the daemon binary at /usr/bin/eGTouchD but does not give you a dependable boot job, so touch can come up before the daemon does, or not at all after a reboot. Create a proper systemd unit:

sudo systemctl edit --force --full eGTouch.service

Paste in the following. The important parts are that it runs early (Before=sysinit.target), it is a forking service that matches how eGTouchD backgrounds itself, and it restarts if it ever dies:

[Unit]
Documentation=man:systemd-sysv-generator(8)
SourcePath=/usr/bin/eGTouchD
DefaultDependencies=no
Before=sysinit.target
After=apparmor.service

[Service]
Type=forking
Restart=always
RestartSec=5
StartLimitInterval=60s
StartLimitBurst=3
TimeoutSec=0
IgnoreSIGPIPE=no
KillMode=process
GuessMainPID=no
RemainAfterExit=no
User=root
Group=root
ExecStart=/usr/bin/eGTouchD start
ExecReload=/usr/bin/eGTouchD restart
ExecStop=/usr/bin/eGTouchD stop

[Install]
WantedBy=multi-user.target

Enable and start it, then reboot to prove it comes up on its own:

sudo systemctl enable eGTouch.service
sudo systemctl restart eGTouch.service
sudo reboot

Checking the display side

While you are here it is worth confirming the display modes the panel is offering, as a touch panel driven over VGA will often advertise a pile of resolutions and the compositor picks one for you. On a Wayland compositor the mode list shows up in its log, for example:

gbm-kms: Output: VGA-1 (connected)
gbm-kms:   Mode: 1920x1080@59.93
gbm-kms:   Mode: 1680x1050@59.88
gbm-kms:   Mode: 1280x1024@60.01
gbm-kms:   Mode: 1024x768@60.00

If touch coordinates end up offset or mirrored, it is almost always a mismatch between the resolution the panel is running at and the one it was calibrated against, so pin the display to a single known mode and recalibrate at that mode rather than chasing it in software.