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Modem Trace Backend

Overview

The Modem Trace Backend sample demonstrates how to add a user-defined modem trace backend to an application.

The sample implements and selects a custom trace backend to receive traces from the modem. For demonstration purposes, the custom trace backend counts the number of bytes received and calculates the data rate of modem traces received. The CPU utilization is also measured. The byte count, data rate, and CPU load are periodically printed to terminal using a delayable work item and the system workqueue.

The custom trace backend is implemented in modem_trace_backend/src/trace_print_stats.c. However, it is possible to add a custom modem trace backend as a library and use it in more than one application. See Adding custom trace backends for details.

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 Trace Backend 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_trace_backend

    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
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    All pins have been configured as non-secure
Booting TF-M v2.1.0
[Sec Thread] Secure image initializing!
TF-M Float ABI: Hard
Lazy stacking enabled
*** Booting nRF Connect SDK v2.9.99-98a5e50b9ac1 ***
*** Using Zephyr OS v3.7.99-693769a5c735 ***
Modem trace backend sample started
Initializing modem library
Custom trace backend initialized
Connecting to network
LTE mode changed to 1
Traces received:  11.9kB, 23.8kB/s, CPU-load:  2.65%
Traces received:  15.2kB,  6.6kB/s, CPU-load:  1.03%
Traces received:  18.4kB,  6.3kB/s, CPU-load:  1.03%
Traces received:  26.2kB, 15.5kB/s, CPU-load:  0.99%
Traces received:  27.9kB,  3.3kB/s, CPU-load:  0.94%
Traces received:  66.5kB, 76.4kB/s, CPU-load:  2.67%
Traces received: 103.7kB, 73.7kB/s, CPU-load:  2.79%
Traces received: 141.7kB, 75.2kB/s, CPU-load:  2.89%
Traces received: 180.0kB, 76.1kB/s, CPU-load:  2.83%
Traces received: 217.9kB, 74.9kB/s, CPU-load:  2.83%
LTE mode changed to 0
Custom trace backend deinitialized
Bye