How-To Display

Description

The Pi-Tron CM5 can be obtained in different configurations and variants, two such variants are the Pi-Tron CM5 with a Kontron display or the DL Pi-Tron CM5.

In both products, a display is connected to the Pi-Tron CM5 board's Family LVDS interface, which allows access to the displays backlight and touch controller. While the PCA9685 chip is accessible right after activating the I2C bus of the Raspberry Pi, the touch controller requires a custom device tree file, to switch the driver into polling mode, instead of interrupt mode. The default overlay file offers no option to activate the polling function of the driver.

CM4 / CM5 compatibility

Although the CM5 can be used as a drop in replacement for the CM4, some GPIOs are different. For example GPIO 44/45 where I2C 0 is on the CM4, the CM5 uses GPIO38/39 and I2C 6 from the RP1 chip.

Requirements

Pi-Tron CM5 with a Kontron Family HDMI touchscreen display connected to the Family LVDS interface or a DL Pi-Tron CM5.
24 volts power supply with 2 pin power plug for the device.
Development computer with network access to the device or alternatively connect an HDMI monitor, mouse and keyboard.
To login into the device via network, it is requires that the SSH server is running.
An active Internet connection to install additional software and to get the current time and date.
The PCA9685 PWM chip is connected to I2C bus 1 and has the address 0x40.
The Goodix GT911 touch controller is connected to I2C bus 6 on GPIOs 38/39 and has the address 0x14.
- There is currently no overlay for the I2C 6, the Git repo mentioned below contains a custom overlay for this.

How-To

Installing the git program allows the user to clone the Pi-Tron CM5 display repository and download all needed installation files.

sudo apt update
sudo apt install git

Now the Pi-Tron CM5 display repository can be cloned:

cd ~
git clone https://git.kontron-electronics.de/sw/ked/raspberry-pi/pi-tron/cm5/display.git

Depending on the integrated touch controller, the appropriate overlay and/or driver has to be installed.

For a Goodix touch a custom overlay file is needed, which is located in the following folder:

cd ~/display/goodix-gt911/

install-procedure

Running the install script will install a service which activates the backlight of the display on boot and builds a custom Goodix GT911 overlay file and copies it to the overlay folder. The install script was made for Raspberry Pi Bookworm and later.

chmod +x install.sh
sudo ./install.sh

After the install completes, the system will be restarted automatically. During the next boot the displays backlight should turn on and if a Raspberry Pi OS with desktop was used as the base OS, the desktop should be visible and the touch is active and allows moving the mouse cursor with one finger.