# Raspberry Pi 疑难解答指南

本指南提供在 Raspberry Pi 设备上运行物联网项目时常见问题的解决方案。  
它针对正在学习 IoT-For-Beginners 课程的初学者设计，但对一般 Pi 开发也很有用。

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## 1. 安装和依赖错误

### ❗ `ModuleNotFoundError: No module named 'xyz'`
当所需的 Python 模块未安装时会发生此问题。

**解决方案**
```bash
pip3 install <module_name>

 Permission denied when running scripts

Often caused by accessing GPIO, I2C or system hardware without elevated privileges.
Quick fix:
sudo python3 script.py

Recommended fix (no sudo needed every time):
sudo usermod -aG gpio,i2c,spi $USER
sudo reboot

2. GPIO / I2C / SPI Not Working
❗ RuntimeError: No access to GPIO

Add user to GPIO group:
sudo usermod -aG gpio $USER
sudo reboot

❗ I2C / SPI devices not detected

Enable interfaces:
sudo raspi-config
→ Interface Options
→ Enable I2C / Enable SPI

Check if I2C device appears:
i2cdetect -y 1

3. Camera / Video Issues
❗ Camera not detected or fails to start

Enable camera interface:
sudo raspi-config
→ Interface Options → Camera → Enable
sudo reboot

Check if camera is visible:
vcgencmd get_camera

4. Wi-Fi / SSH / Connectivity Problems
| Problem                          | Fix                                           |
| -------------------------------- | --------------------------------------------- |
| SSH connection refused           | `sudo raspi-config → Interface Options → SSH` |
| Device not showing on network    | Check IP using: `hostname -I`                 |
| Slow Wi-Fi / unstable connection | Prefer 2.4 GHz band, update OS                |
| Unable to access Pi headless     | Add `ssh` file to boot partition              |


5. Performance Issues
Raspberry Pi running slow / laggy

Close unused applications

Reduce background services

Use Lite OS if no desktop needed

Ensure sufficient power supply (5V/3A or better)

Check CPU load:
top
htop

Storage issues:
sudo apt autoremove
sudo apt clean
df -h

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