Internet of Things (IoT) & Embedded Systems Architecture
Power Management in Embedded Linux
Battery-powered Linux devices live or die by idle power. Most of the budget goes to wake-ups, radios, and peripherals that never truly sleep. Tuning governors, suspend states, and clock gating is measurable work, and the biggest wins usually come from removing activity rather than from kernel knobs.
Nyckelpunkter
- Measure current draw in every state: active, idle, suspended, and off.
- Find wake-up sources with powertop or tracing before changing governor settings.
- Batch work so the CPU wakes less often instead of running longer.
- Disable unused peripherals and radios at the device tree or driver level.
- Choose suspend states the hardware actually supports and verify resume reliability.
- Account for radio transmit power, which often dominates the budget.
- Test across temperature, since battery behavior changes at extremes.
- Track energy per useful action, not just average current.
Vanliga frågor
Which governor saves the most power?
It depends on workload. Idle time and wake-up count matter more than the governor name.
Why does suspend drain the battery?
Peripherals or wake sources may remain active, or the suspend state may be shallow.
Can I disable the network radio entirely?
Yes, if the application tolerates store-and-forward or scheduled connections.
How do I measure power properly?
Use an inline power monitor on the battery rail, not a USB meter with its own overhead.
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