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nRF5x System Off demo

Overview

This sample can be used for basic power measurement and as an example of deep sleep on Nordic platforms. The functional behavior is:

  • Busy-wait for 2 seconds

  • Sleep for 2 seconds without device power control

  • Sleep for 2 seconds after turning UART off, which reduces current draw by a couple hundred uA

  • Turn the system off after enabling wakeup through a button press

A power monitor will be able to distinguish among these states.

This sample also demonstrates the use of a SYS_INIT() call to disable the deep sleep functionality before the kernel starts, which prevents the board from powering down during initialization of drivers that use unbounded delays to wait for startup.

Requirements

This application uses nRF51 DK or nRF52 DK board for the demo.

Building, Flashing and Running

west build -b nrf52dk_nrf52832 samples/boards/nrf52/system_off
west flash

Running:

  1. Open UART terminal.

  2. Power Cycle Device.

  3. Device will demonstrate two activity levels which can be measured.

  4. Device will demonstrate long sleep at minimal non-off power.

  5. Device will turn itself off using deep sleep state 1. Press Button 1 to wake the device and restart the application as if it had been powered back on.

Sample Output

nRF52 core output

*** Booting Zephyr OS build v2.3.0-rc1-204-g5f2eb85f728d  ***

nrf52dk_nrf52832 system off demo
Busy-wait 2 s
Busy-wait 2 s with UART off
Sleep 2 s
Sleep 2 s with UART off
Entering system off; press BUTTON1 to restart