Device Power Management: Journey to 5uA
summary
A Nordic nRF52840 board with Bluetooth, LoRaWAN, GNSS, SD, sensors and charging is brought from milliamps down to about 5–6 µA idle by combining hardware power domains and per‑device power switches, enabling Zephyr device runtime PM (including the PM device runtime Auto and PM device_driver_init helpers), and implementing PM callbacks in drivers. Measurements use an Ai‑Arc power meter; surprises include UART RX costing ~1.1 mA, programmer LEDs/JTAG adding hundreds of µA, and floating pins causing odd analog currents. A validation app confirms return to low power.
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chapters (18)
- 0:00Device power management intro
- 1:03Power consumption importance
- 3:07Hardware overview & power budget
- 8:32Power domains & software setup
- 10:39Runtime power mgmt in Zephyr
- 16:36Driver power management
- 20:11Cheap power reduction wins
- 22:58Debugging power issues iteratively
- 30:24Validating low-power states
- 32:53Low-power app firmware
- 34:04Q&A: Device tree power options
- 35:27Q&A: Low-power drivers
- 37:33Q&A: Power regression testing
- 39:20Q&A: Power state debugging
- 40:22Q&A: Power simulators
- 42:55Q&A: Future of power mgmt
- 44:23Q&A: Nordic SoC power mgmt
- 45:06Q&A: Nuclear power fixes
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