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Serial LTE Modem

Overview

The Serial LTE Modem (SLM) application can be used to emulate a stand-alone LTE modem on the nRF9151 Connect Kit. The application accepts both the modem-specific AT commands and proprietary AT commands. The AT commands are documented in the following guides:

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 U.FL cabled GNSS Antenna (included in the box)
  • 1x USB-C Cable
  • Serial Studio v3.0.6 or newer
  • 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. Attach the U.FL cabled GNSS Antenna.
  4. Connect the nRF9151 Connect Kit to the computer with a USB-C cable.

Building the application

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

Use the following steps to build the Serial LTE Modem application 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 application 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 applications/serial_lte_modem

    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 application.

    Note

    This application 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 application 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 application 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 application, test it by performing the following steps:

  1. Start Serial Studio application, and complete the following steps:

    1. Select DEVICE SETUP -> Serial Port.
    2. Select FRAME PARSING -> No Parsing.
    3. Select the correct serial port that your computer uses to communicate with the nRF9151 SiP from the COM Port drop-down list.
    4. Select Baud Rate -> 115200, Data Bits -> 8, Parity -> None, Stop Bits -> 1, Flow Control -> None.
    5. Select Send DTR Signal.
    6. Click Connect .
    7. Select Line Ending -> CR+NL.

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

  3. Observe that the board sends a Ready\r\n message on the console.

  4. Send AT commands and observe the responses from the board. See Testing scenarios for typical test cases.