Raspberry Pi OS imaging headless SSH setup hostname configuration package updates systemd service basics journalctl logs environment variables Python virtual environment

GPIO pin numbering digital output LED digital input button pull-up resistor button debounce PWM LED brightness GPIO cleanup edge detection

I2C device scan I2C sensor read SPI overview SPI transfer UART serial read 1-Wire temperature sensor ADC via external chip sensor calibration

cron scheduled task systemd autostart app camera capture filesystem data logging MQTT publish MQTT subscribe HTTP sensor endpoint local SQLite logging

static IP concept mDNS hostname Wi-Fi configuration SSH key authentication SFTP file transfer Nginx reverse proxy firewall with ufw network diagnostics

servo control ultrasonic distance sensor relay module safety RGB LED mixing buzzer tone PIR motion sensor rotary encoder safe shutdown button