Hey there! Let's fix that annoying edge-button touch issue with your Raspberry Pi + Egalax touchscreen setup. I’ve dealt with similar problems before, so here’s a step-by-step calibration plan tailored to your setup:

1. Start with the Official Egalax Calibration Tool #

Egalax screens come with a dedicated calibration utility that’s usually the quickest fix, especially for edge alignment:

• Open a terminal and run: sudo egalax-calibrator (if it’s not installed first, run sudo apt install egalax-calibrator)
• Follow the on-screen prompts to tap all calibration points, especially the ones at the extreme edges—this is likely where your previous y-axis flip missed fine-tuning edge coordinates
• After calibration, restart the touch service to apply changes: sudo systemctl restart egalax-touchscreen

2. Manual Coordinate Adjustment with xinput #

If the official tool doesn’t nail it, we can tweak the coordinate mapping directly via xinput for precision:

1. First, find your touch device’s ID:

   xinput list
   

   Look for a device named something like "EETI eGalax Touch Screen" and note its ID (e.g., 10)
2. Check your current transformation matrix (you’ll see the y-axis flip you applied here):

   xinput list-props <DEVICE_ID> | grep "Coordinate Transformation Matrix"
   

   A standard matrix is 1 0 0 0 1 0 0 0 1; your flipped y-axis version is probably 1 0 0 0 -1 1 0 0 1
3. Fine-tune edge offsets:
   If your edge taps are registering too far inward, adjust the offset values in the matrix. For example:
   • If the left edge is unresponsive, tweak the 3rd value (x-offset) to -0.02
   • If the bottom edge is off, adjust the 6th value (y-offset) to 1.02
     Run this command to test (replace <DEVICE_ID> with your actual ID):

   xinput set-prop <DEVICE_ID> "Coordinate Transformation Matrix" 1 0 -0.02 0 -1 1.02 0 0 1
   

   Adjust the offset values in small increments (±0.01 to ±0.05) and test edge taps each time until they line up perfectly
4. Save the settings permanently:
   Create a config file in /usr/share/X11/xorg.conf.d/ named 99-egalax-calibration.conf with this content (replace the matrix with your working values):

   Section "InputClass"
       Identifier "Egalax Touch Screen"
       MatchProduct "EETI eGalax Touch Screen"
       Driver "libinput"
       Option "TransformationMatrix" "1 0 -0.02 0 -1 1.02 0 0 1"
   EndSection
   

   Reboot your Pi to make the changes stick

3. Kivy-Specific Input Calibration #

If system-level calibration is solid but Kivy still isn’t registering edge taps correctly, adjust the app’s input settings:

• In your Kivy app’s main.py, add this at the start to tweak calibration:

  from kivy.config import Config
  # Disable mouse emulation if needed
  Config.set('input', 'mouse', 'mouse,multitouch_on_demand')
  # Replace <YOUR_TOUCH_DEVICE_NAME> with the name from xinput list
  Config.set('input', '<YOUR_TOUCH_DEVICE_NAME>', 'mtdev,calibration=0.02,0.02,-0.02,-0.02')
  

  The calibration values follow the format: x_min_offset, y_min_offset, x_max_offset, y_max_offset—adjust based on your test results
• Alternatively, edit the global Kivy config file at ~/.kivy/config.ini under the [input] section to apply this to all Kivy apps:

  <YOUR_TOUCH_DEVICE_NAME> = mtdev,calibration=0.02,0.02,-0.02,-0.02
  

4. Verify Your Calibration #

After each adjustment:

• Keep the cursor enabled and use your stylus to tap the problematic edge button—check if the cursor lands exactly on the button
• Repeat tweaks until every edge input registers correctly

内容的提问来源于stack exchange，提问作者Superleggera