Touch Problems

Touch Not Working

Verify Touch Controller Detection

1. Check kernel messages

   dmesg | grep -i goodix

   Should show GT9271 initialization.

2. Check input devices

   cat /proc/bus/input/devices | grep -A5 "Goodix"

   Should show “Goodix Capacitive TouchScreen”.

3. List input events

   ls /dev/input/event*

4. Test touch input

   sudo apt install evtest
   sudo evtest
   # Select touch device, then tap screen

Touch Controller Not Found

If GT9271 isn’t detected:

1. Check I2C bus

   i2cdetect -y 10

   Should show device at 0x14 or 0x5D.

2. Power cycle display

   • Disconnect 5V power cable
   • Wait 5 seconds
   • Reconnect power
   • Reboot Pi

3. Reseat DSI cable

   • Touch uses I2C lines in DSI cable
   • Poor connection causes touch failure

4. Check for I2C errors

   dmesg | grep -i "i2c\|error"

Touch Calibration Issues

Touch Offset from Display Position

When you tap a spot but the cursor appears elsewhere, you need calibration:

# Create udev rule
sudo nano /etc/udev/rules.d/99-waveshare-touch.rules

Add the appropriate matrix for your rotation:

# 0° (no rotation)
ENV{ID_INPUT_TOUCHSCREEN}=="1", ENV{LIBINPUT_CALIBRATION_MATRIX}="1 0 0 0 1 0"

# 90° rotation
ENV{ID_INPUT_TOUCHSCREEN}=="1", ENV{LIBINPUT_CALIBRATION_MATRIX}="0 -1 1 1 0 0"

# 180° rotation
ENV{ID_INPUT_TOUCHSCREEN}=="1", ENV{LIBINPUT_CALIBRATION_MATRIX}="-1 0 1 0 -1 1"

# 270° rotation
ENV{ID_INPUT_TOUCHSCREEN}=="1", ENV{LIBINPUT_CALIBRATION_MATRIX}="0 1 0 -1 0 1"

Reboot after saving.

Touch Inverted/Mirrored

Symptom	Matrix to Try
X inverted	-1 0 1 0 1 0
Y inverted	1 0 0 0 -1 1
Both inverted	-1 0 1 0 -1 1

Touch Works But Wrong Direction

The rotation matrix must match the display rotation. If display is rotated 90° but touch isn’t calibrated:

• Touch at top → registers as right side
• Touch at left → registers as top

Apply the matching calibration matrix.

Multitouch Issues

Only Single Touch Works

1. Check touch mode

   • Open Screen Configuration
   • Go to Touchscreen tab
   • Enable “Multitouch” mode

2. OS limitation

   • Some applications only support single touch
   • Web browsers may limit touch points

Gestures Not Working

Multitouch gestures require:

• Multitouch mode enabled
• Compatible application
• Proper libinput configuration

# Check libinput settings
libinput list-devices | grep -A10 "Goodix"

Touch Sensitivity

Touch Requires Hard Press

The capacitive touch should respond to light touches. If it requires pressure:

• Screen protector interfering (remove or use compatible type)
• Gloves preventing capacitive detection
• Touch IC firmware issue (rare)

Ghost Touches / Random Inputs

Caution

Ghost touches often indicate electrical interference or hardware problems.

Causes:

• Poor grounding
• EMI from nearby electronics
• Static discharge
• Hardware defect

Solutions:

1. Ensure proper grounding through GPIO
2. Move away from EMI sources
3. Contact Waveshare if persistent

Touch Lag

Delayed Response

Touch should respond within ~10ms. Lag indicates:

1. High CPU load

   top
   # Check for processes using high CPU

2. I2C bus issues

   • Other I2C devices causing conflicts
   • Long I2C cable runs

3. Driver issues

   • Update to latest Raspberry Pi OS
   • Try Waveshare pre-built image

Testing Touch

Using evtest

sudo apt install evtest
sudo evtest /dev/input/event0  # Adjust number

Touch the screen and observe coordinates. You should see:

• ABS_MT_POSITION_X
• ABS_MT_POSITION_Y
• ABS_MT_TRACKING_ID

Using xinput (X11)

xinput list
xinput test "Goodix Capacitive TouchScreen"

Graphical Test

# Install mtdev-tools
sudo apt install mtdev-tools

# Run graphical test
mtview /dev/input/event0