Troubleshooting¶

Editor Won't Start¶

• Verify Qt 6.5+ is installed correctly
• On Linux: run ldd ./PiPLC to check for missing dependencies
• On Windows: run windeployqt PiPLC.exe

Can't Connect to Remote Engine¶

• Check that piplc-engine is running: systemctl status piplc-engine
• Check firewall: sudo ufw allow 9100/tcp
• Verify IP and port in the WebSocket URL
• Check logs: journalctl -u piplc-engine -f

GPIO Not Working¶

• Verify libgpiod is installed: gpiodetect
• Check permissions — your user must be in the gpio group:

  sudo usermod -aG gpio $USER
  

• Verify the engine was compiled with PIPLC_HAS_GPIO
• On platforms without GPIO, VirtualIOProvider is used automatically

I2C Device Not Detected (Explorer HAT Pro)¶

• Enable I2C: sudo raspi-config nonint do_i2c 0
• Verify detection: i2cdetect -y 1
• Add user to i2c group: sudo usermod -aG i2c $USER

Simulation Is Slow¶

• Reduce the number of active rungs
• Increase scan time (e.g., 50ms or 100ms)
• Check CPU usage — should be <25% on Pi 3B+, <15% on Pi 4

Motor Not Responding to Speed Changes (Explorer HAT Pro)¶

• The speed word (N:4 or N:5) must be written every scan with a MOV instruction
• The direction bit (O:0/8-11) must be ON for the desired direction

ADC Values Are Noisy¶

• Check wiring to the analog pads
• The ADS1015 uses single-shot mode — readings are sequential

System Verification¶

# Service status
sudo systemctl status piplc-engine

# Engine logs
journalctl -u piplc-engine --since "1 hour ago"

# Available GPIO
gpiodetect
gpioinfo /dev/gpiochip0

# I2C devices
i2cdetect -y 1

# Run tests
cd build && ctest --output-on-failure