Troubleshooting XPT2046 Touchscreen Calibration with HamPi on Raspberry Pi 4

- November 27, 2024

Troubleshooting XPT2046 Touchscreen Calibration with HamPi on Raspberry Pi 4

Touchscreens can be an excellent addition to your Raspberry Pi projects, but getting them calibrated properly can be a bit of a headache, especially with models like the XPT2046. If you're using an XPT2046 touchscreen with your Raspberry Pi 4, running an operating system like HamPi (based on Raspbian OS), and struggling to calibrate it, this guide is for you. Let's walk through the process of getting your touchscreen properly calibrated.

Step 1: Install the Necessary Drivers

Before jumping into calibration, ensure the drivers for the touchscreen are installed. The xserver-xorg-input-evdev package is often a great starting point for enabling touch input. Open a terminal and run the following commands:

$ sudo apt update  
$ sudo apt install xserver-xorg-input-evdev

This ensures the system can process touch inputs effectively.

Step 2: Check if the System Recognizes the Touchscreen

Next, verify that your Raspberry Pi recognizes the touchscreen as an input device. Run the following command to list all input devices:

$ ls /dev/input/

Look for an entry like eventX (where X is a number). This file represents the input for your touchscreen. If you don't see it, there might be an issue with the hardware connection or driver compatibility.

Step 3: Calibrate the Touchscreen

To align the touchscreen’s input with the display, install the xinput-calibrator tool. This utility provides an easy-to-use interface for touch calibration:

$ sudo apt install xinput-calibrator

Once installed, run the calibrator with:

$ DISPLAY=:0 xinput_calibrator

Follow the on-screen instructions, touching the points indicated. When the calibration is complete, the tool will output configuration settings.

Step 4: Save the Calibration Settings

The calibration tool generates a section of configuration text that needs to be saved. Create or edit a configuration file to store these settings:

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

Add the following content, replacing placeholders with the actual values from the calibration output:

(nano)

Section "InputClass"  
    Identifier "calibration"  
    MatchProduct "YOUR_TOUCHSCREEN_NAME"  
    Option "Calibration" "CALIBRATION_VALUES"  
    Option "SwapAxes" "0"  
EndSection

Make sure to replace YOUR_TOUCHSCREEN_NAME with your device name and CALIBRATION_VALUES with the values provided by the calibrator.

Step 5: Enable SPI (if Necessary)

For some XPT2046 touchscreens that rely on SPI, you’ll need to enable SPI in the Raspberry Pi configuration. Run:

$ sudo raspi-config

Navigate to Interface Options > SPI, enable it, and reboot your Raspberry Pi:

$ sudo reboot

Step 6: Test the Calibration

To confirm everything is working, use the evtest tool to monitor touch input and ensure the calibration matches your display. Install the tool with:

$ sudo apt install evtest

Then, test your touchscreen:

$ sudo evtest /dev/input/eventX

Replace /dev/input/eventX with the specific input file for your touchscreen. Touch the screen to see if the coordinates are registered accurately.