Upgrading modem firmware using MCUboot serial recovery

nrfutil device can be used to upgrade modem firmware on devices with the mcuBoot and modem device traits.

Note

This is a programming method for Nordic Thingy:91 X and Nordic Thingy:91.

The procedure happens over the MCUboot serial recovery, a mode in which the bootloader is waiting for a new image upload to start. In this mode, the new image is transferred through an USB CDC ACM class instance. The bootloader overwrites the existing application located on the primary slot with the new application image. If the transfer is interrupted, the device cannot boot the incomplete application, and the image upload must be performed again.

Complete the following steps:

Prepare the nRF9160 System in Package (SiP) modem firmware file or download it from Nordic Semiconductor website.
- For Nordic Thingy:91, download it from Downloads tab > nRF9160 SiP modem firmware.
- For Nordic Thingy:91 X, download it from Downloads tab > nRF91x1 SiP LTE firmware.
Connect your device to your computer using an USB cable.
List the devices connected to the system by running the following command:
```
nrfutil device list --traits mcuBoot,modem
```
The serial number of the device will be referenced as <serial_number> in the programming step. For Nordic Thingy:91, the serial number is composed of 20 characters (for example, THINGY91_C2E0AC7F599). For Nordic Thingy:91 X, it has 21 characters (for example, THINGY91X_C2E0AC7F599).
Put the SiP of the Thingy device in the application serial recovery mode by holding in the SW3 button while powering it off and on.

Program the modem firmware file (<modem_fw_file_name>) by running the following command:

nrfutil device program --firmware <modem_fw_file_name> --serial-number <serial_number>

For example, for Nordic Thingy:91, the command could look like this:

nrfutil device program --firmware mfw_nrf9160_1.3.3.zip --serial-number THINGY91_C2E0AC7F599