Design a power state machine for a battery-powered IoT device.

A power state machine optimizes energy consumption by transitioning between power modes based on activity. States: Active: Full speed operation, all peripherals enabled. Idle: CPU in low-power mode, peripherals running, fast wake. Light Sleep: Reduced clock, most peripherals off, quick wake. Deep Sleep: Minimal power, RTC only, longer wake time. Shipping/Storage: Lowest power, needs physical trigger to wake. Transitions triggered by: Activity detection (sensor, user input). Communication events (data to send, message received). Timers (scheduled operations). Low battery condition. Implementation: typedef enum { STATE_ACTIVE, STATE_IDLE, STATE_LIGHT_SLEEP, STATE_DEEP_SLEEP } PowerState; Consider: Hysteresis to prevent rapid transitions. Wake source configuration per state. Peripheral state preservation across sleep. Timeout-based automatic sleep escalation. Battery monitoring integration. Real devices: Measure current in each state, optimize time allocation based on use case.