Wakeup

IoT devices often need to save power. When the screen is off, the network is idle, or sensor sampling is infrequent, the system wants to enter a low-power state.

From the application point of view, sleep can look like “pause for a while and continue when an event arrives.” Inside the system, much more happens.

Device sleep is not just pausing the CPU. The system may stop CPU cores, lower frequencies, gate peripheral clocks, cut power domains, save register state, freeze user processes, run driver suspend callbacks, and leave only a small set of wake sources enabled.