zephyr

History

Peter Bigot bdba2e63f6 samples: nrf: system_off: add RAM retention example for nRF52 Add an object to retain data across both reboots and entry to SYSTEM_OFF. This only works on nRF52, since nRF51 and nRF53 require different low-level operations to configure RAM retention. Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>		2021-02-17 14:34:31 +01:00
..
src	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00
CMakeLists.txt	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00
Kconfig	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00
README.rst	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00
prj.conf	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00
sample.yaml	samples: nrf: system_off: add RAM retention example for nRF52	2021-02-17 14:34:31 +01:00

README.rst

.. _nrf-system-off-sample:

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 :c:func:`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.

RAM Retention
=============

On nRF52 platforms this also can demonstrate RAM retention.  By selecting
``CONFIG_APP_RETENTION=y`` state related to number of boots, number of times
system off was entered, and total uptime since initial power-on are retained
in a checksummed data structure.  The POWER peripheral is configured to keep
the containing RAM section powered while in system-off mode.

Requirements
************

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

Building, Flashing and Running
******************************

.. zephyr-app-commands::
   :zephyr-app: samples/boards/nrf52/system_off
   :board: nrf52dk_nrf52832
   :goals: build flash
   :compact:

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
-----------------

.. code-block:: console

   *** 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