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Modem Battery

Overview

The Modem Battery sample demonstrates how to obtain the following battery related information from the modem using the Modem battery library:

  • Modem battery voltage
  • Modem battery voltage low level notifications
  • Power-off warnings

How it works

The sample first calls the modem_battery_low_level_handler_set() and modem_battery_pofwarn_handler_set() functions to set the respective handlers, and then sets up the workqueues used to handle the low level battery voltage notifications and the power-off warning notifications. The sample then initializes the Modem library. Next, it enters a state machine that measures the modem battery voltage at every iteration and then executes an activity based on that. The first activity (init_activity()) sets the modem to receive-only mode if the battery voltage drops below the low level threshold or to normal mode if it rises above the threshold and updates the state accordingly.

Then, depending on the modem’s battery voltage, the modem switches mode according to the following conditions:

  • If the modem is in normal mode and the battery voltage drops below the low level threshold, the modem switches to receive-only mode.
  • If the modem is in receive-only mode and the battery voltage is below the low level threshold, the application periodically checks the battery voltage and switches state if it rises above the low level threshold.
  • If the modem is in receive-only mode and the battery voltage is above the low level threshold, the application executes a connectivity evaluation and if the conditions are either normal (7), good (8), or excellent (9), the modem switches to normal mode. When connectivity conditions are poor, the number of packets re-transmitted is higher thus causing an increase in power consumption, which must be avoided when battery voltage is not at an adequately safe level. Full connectivity is recommended when battery voltage is at a sufficient level.
  • If the modem is in normal mode and the battery voltage is above the low level threshold, the application executes some IP traffic (DNS lookup) to maintain an active LTE connection. The modem performs background monitoring of the battery voltage and sends a notification of low level in case it drops below the set threshold.
  • If the modem battery voltage drops below the power-off warning level, the modem is automatically set offline by the hardware.
  • If the modem battery voltage rises above the power-off warning level, the modem is set to receive-only mode and initialized.

Requirements

Before you start, check that you have the required hardware and software:

  • 1x nRF9151 Connect Kit
  • 1x nano-SIM card with LTE-M or NB-IoT support
  • 1x U.FL cabled LTE-M/NB-IoT/NR+ Flexible Antenna (included in the box)
  • 1x USB-C Cable
  • A computer running macOS, Ubuntu, or Windows 10 or newer

Set up your board

  1. Insert the nano-SIM card into the nano-SIM card slot.
  2. Attach the U.FL cabled LTE-M/NB-IoT/NR+ Flexible Antenna.
  3. Connect the nRF9151 Connect Kit to the computer with a USB-C cable.

Building the sample

To build the sample, follow the instructions in Getting Started Guide to set up your preferred building environment.

Use the following steps to build the Modem Battery sample on the command line.

  1. Open a terminal window.

  2. Go to NCS-Project/nrf9151-connectkit repository cloned in the Getting Started Guide.

  3. Build the sample using the west build command, specifying the board (following the -b option) as nrf9151_connectkit/nrf9151/ns.

    west build -p always -b nrf9151_connectkit/nrf9151/ns samples/modem_battery

    The -p always option forces a pristine build, and is recommended for new users. Users may also use the -p auto option, which will use heuristics to determine if a pristine build is required, such as when building another sample.

    Note

    This sample has Cortex-M Security Extensions (CMSE) enabled and separates the firmware between Non-Secure Processing Environment (NSPE) and Secure Processing Environment (SPE). Because of this, it automatically includes the Trusted Firmware-M (TF-M).

  4. After building the sample successfully, the firmware with the name merged.hex can be found in the build directory.

Flashing the firmware

Set up your board before flashing the firmware. You can flash the sample using west flash:

west flash

Tip

In case you wonder, the west flash will execute the following command:

pyocd load --target nrf91 --frequency 4000000 build/merged.hex

Testing

After programming the sample, test it by performing the following steps:

  1. Open up a serial terminal, specifying the correct serial port that your computer uses to communicate with the nRF9151 SiP:

    1. Start PuTTY.

    2. Configure the correct serial port and click Open:

    Open up a terminal and run:

    screen <serial-port-name> 115200

    Open up a terminal and run:

    screen <serial-port-name> 115200

  2. Press the DFU/RST button to reset the nRF9151 SiP.

  3. Observe the output of the terminal. You should see the output, similar to what is shown in the following:

    Terminal
     1
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 5
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 8
 9
10
11
12
13
14
15
16
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22
    All pins have been configured as non-secure
Booting TF-M v2.1.0
[Sec Thread] Secure image initializing!
*** Booting nRF Connect SDK v2.9.99-98a5e50b9ac1 ***
*** Using Zephyr OS v3.7.99-693769a5c735 ***
Battery sample started
Initializing modem library
Battery voltage: 4520
Setting modem to normal mode...
Normal mode set.
Connected.
Battery voltage: 4524
Executing DNS lookup for 'example.com'...
Battery voltage: 4520
Executing DNS lookup for 'google.com'...
Battery voltage: 4516
Executing DNS lookup for 'apple.com'...
Battery voltage: 4516
Executing DNS lookup for 'amazon.com'...
Battery voltage: 4520
Executing DNS lookup for 'microsoft.com'...
...