Interface MCU Firmware¶

Overview¶

This guide walks you through building and running the Interface MCU Firmware which enables a CMSIS-DAP interface for debug and programming, a USB-UART bridge for terminal emulation and an Interface Shell for accessing board-specific functionality.

How it works¶

The nRF54L15 Connect Kit comes with an nRF52820-based Interface MCU. The Interface MCU Firmware is running on the nRF52820. It implements a CMSIS-DAP interface for debugging and programming the nRF54L15. It also exposes two USB CDC ACM devices, one acts as a UART bridge between the host and the nRF54L15, the other enables an Interface Shell for accessing board-specific functionality.

The Interface MCU also comes pre-programmed with the UF2 Bootloader, an easy-to-use and self-upgradable bootloader that can be used to update the firmware by just copying the .uf2-format images to the flash drive without using an external programmer.

The following figure describes the functional architecture of the Interface MCU:

Requirements¶

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

• 1x nRF54L15 Connect Kit
• 1x USB-C Cable
• A computer running macOS, Ubuntu, or Windows 10 or newer

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 Interface MCU Firmware on the command line.

1. Open a terminal window.

2. Go to NCS-Project/nrf54l15-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 nrf54l15_connectkit/nrf52820.

   west build -p always -b nrf54l15_connectkit/nrf52820 applications/ifmcu_firmware
   

   Tip

   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.

4. After building the application successfully, the firmware with the name zephyr.uf2 can be found in the build/ifmcu_firmware/zephyr directory.

Flashing the firmware¶

The application is compatible with the UF2 Bootloader, so that you can easily flash the firmware by just copying the zephyr.uf2 file to the flash drive without using an external programmer.

To flash the firmware, complete the following steps:

1. Push and hold the DFU/RST button and connect your board to the USB port of your computer. Release the DFU/RST button after your board is connected.

2. It will mount as a Mass Storage Device called UF2BOOT. The RGB LED is breathing in green.

3. Drag and drop zephyr.uf2 onto the UF2BOOT volume. The RGB LED blinks green rapidly during programming.

4. The application starts running after the firmware programming is completed.

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$ cp build/ifmcu_firmware/zephyr/zephyr.uf2 /Volumes/UF2BOOT
cp: /Volumes/UF2BOOT/zephyr.uf2: fcopyfile failed: Input/output error
cp: /Volumes/UF2BOOT/zephyr.uf2: fchmod failed: No such file or directory

Usage¶

Using the CMSIS-DAP Interface¶

You can use the CMSIS-DAP Interface to debug or program the nRF54L15.

Before you start, a tool that supports the CMSIS-DAP protocol should be installed. pyOCD v0.38.0 or newer is required. pyOCD will be installed after setting up your development environment in Getting Started Guide.

The following sections show the typical use cases with pyOCD:

• To show the connected devices, use pyocd list:

  Terminal
  1 2 3 4	# Probe/Board Unique ID Target ----------------------------------------------------------------- 0 ZEPHYR IFMCU CMSIS-DAP 820D9A5F0E322B8EFE662 ✔︎ nrf54l Makerdiary nRF54L15 Connect Kit

• To program the nRF54L15 application firmware, use pyocd load:

  pyocd load -t nrf54l <firmware.hex> # (1)!
  

  1. You can also use pyocd flash instead:

     pyocd flash -t nrf54l <firmware.hex>
     

• To erase the entire non-volatile memory (RRAM) of the nRF54L15, run the following command:

  pyocd erase -t nrf54l --chip
  

To learn more about pyOCD, see the pyOCD Documentation.

Using the USB-UART Bridge¶

The primary USB CDC ACM device that the Interface MCU exposes acts as a UART bridge between the host and the nRF54L15.

To see the UART output, connect to the board with a terminal emulator, specifying the correct serial port that your computer uses to communicate with the nRF54L15:

screen <serial-port-name> 115200

screen <serial-port-name> 115200

Using the Interface Shell¶

The secondary USB CDC ACM device that the Interface MCU exposes enables an Interface Shell for accessing the board-specific functionality.

To interact with the Interface Shell, connect to the board with a terminal emulator, specifying the correct serial port that your computer uses to communicate with the shell:

screen <serial-port-name> 115200

screen <serial-port-name> 115200

Type Tab to list all supported commands. When you type a command with --help, the terminal shows its usage, for example i2c --help. For more information about the commands, see the Interface Shell Command Reference.

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ifsh:~$
  bootloader  cfgsync     clear       device      gpio        help
  history     i2c         kernel      rem         reset       resize
  retval      settings    shell       temp        version     viosel
ifsh:~$ i2c --help
i2c - I2C commands
Subcommands:
  scan  : Scan I2C devices
                 Usage: scan <device>
  recover  : Recover I2C bus
                 Usage: recover <device>
  read  : Read bytes from an I2C device
                 Usage: read <device> <addr> <reg> [<bytes>]
  read_byte  : Read a byte from an I2C device
                 Usage: read_byte <device> <addr> <reg>
  direct_read  : Read byte stream directly from an I2C device without writing a
                 register address first
                 Usage: direct_read <device> <addr> [<bytes>]
  write  : Write bytes to an I2C device
                 Usage: write <device> <addr> <reg> [<byte1>, ...]
  write_byte  : Write a byte to an I2C device
                 Usage: write_byte <device> <addr> <reg> <value>
  speed  : Configure I2C bus speed
                 Usage: speed <device> <speed>
ifsh:~$

Interface Shell Command Reference¶

The following table describes all supported commands of the Interface Shell: