93 lines
2.8 KiB
ReStructuredText
93 lines
2.8 KiB
ReStructuredText
.. _boards_nrf_battery:
|
|
|
|
Battery Voltage Measurement
|
|
###########################
|
|
|
|
Overview
|
|
********
|
|
|
|
This sample demonstrates using Nordic configurations of the Zephyr ADC
|
|
infrastructure to measure the voltage of the device power supply. Two
|
|
power supply configurations are supported:
|
|
|
|
* If the board devicetree has a ``/vbatt`` node with compatible
|
|
``voltage-divider`` then the voltage is measured using that divider. An
|
|
example of a devicetree node describing a voltage divider for battery
|
|
monitoring is:
|
|
|
|
.. code-block:: devicetree
|
|
|
|
/ {
|
|
vbatt {
|
|
compatible = "voltage-divider";
|
|
io-channels = <&adc 4>;
|
|
output-ohms = <180000>;
|
|
full-ohms = <(1500000 + 180000)>;
|
|
power-gpios = <&sx1509b 4 0>;
|
|
};
|
|
};
|
|
|
|
* If the board does not have a voltage divider and so no ``/vbatt`` node
|
|
present, the ADC configuration (device and channel) needs to be provided via
|
|
the ``zephyr,user`` node. In this case the power source is assumed to be
|
|
directly connected to the digital voltage signal, and the internal source for
|
|
``Vdd`` is selected. An example of a Devicetree configuration for this case is
|
|
shown below:
|
|
|
|
.. code-block :: devicetree
|
|
|
|
/ {
|
|
zephyr,user {
|
|
io-channels = <&adc 4>;
|
|
};
|
|
};
|
|
|
|
Note that in many cases where there is no voltage divider the digital
|
|
voltage will be fed from a regulator that provides a fixed voltage
|
|
regardless of source voltage, rather than by the source directly. In
|
|
configuration involving a regulator the measured voltage will be
|
|
constant.
|
|
|
|
The sample provides discharge curves that map from a measured voltage to
|
|
an estimate of remaining capacity. The correct curve depends on the
|
|
battery source: a standard LiPo cell requires a curve that is different
|
|
from a standard alkaline battery. Curves can be measured, or estimated
|
|
using the data sheet for the battery.
|
|
|
|
Application Details
|
|
===================
|
|
|
|
The application initializes battery measurement on startup, then loops
|
|
displaying the battery status every five seconds.
|
|
|
|
Requirements
|
|
************
|
|
|
|
A Nordic-based board, optionally with a voltage divider specified in its
|
|
devicetree configuration as noted above.
|
|
|
|
Building and Running
|
|
********************
|
|
|
|
The code can be found in :zephyr_file:`samples/boards/nrf/battery`.
|
|
|
|
.. zephyr-app-commands::
|
|
:zephyr-app: samples/boards/nrf/battery
|
|
:board: thingy52_nrf52832
|
|
:goals: build flash
|
|
:compact:
|
|
|
|
|
|
Sample Output
|
|
=============
|
|
|
|
.. code-block:: console
|
|
|
|
*** Booting Zephyr OS build zephyr-v2.2.0-318-g84219bdc1ac2 ***
|
|
[0:00:00.016]: 4078 mV; 10000 pptt
|
|
[0:00:04.999]: 4078 mV; 10000 pptt
|
|
[0:00:09.970]: 4078 mV; 10000 pptt
|
|
[0:00:14.939]: 4069 mV; 10000 pptt
|
|
[0:00:19.910]: 4078 mV; 10000 pptt
|
|
[0:00:24.880]: 4069 mV; 10000 pptt
|