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2. FW Update Example Tutorial

This example explains the firmware update process for both ABAB and ACAB silicon revisions. Use this example as a reference for integrating TROPIC01 firmware updates into your application. You will learn:

  • How to read the current firmware versions.
  • How to update the firmware using lt_do_mutable_fw_update(), which performs the recommended FW update procedure.
  • How to handle TROPIC01 Maintenance Mode to reduce the attack surface.

TROPIC01 Firmware

For more information about the firmware itself, refer to the TROPIC01 Firmware section.

Firmware Update Precautions

Use a stable power source and avoid disconnecting the TROPIC01 (devkit) or rebooting your host device (computer or microcontroller) during the update. Interrupting the firmware update can brick the device.

Build and Run

Building and running the example

Go to the example's project directory: 

cd examples/stm32/<your_board>/fw_update/

Create a build/ directory and switch to it: 

mkdir build/
cd build/

Open your STM32's serial port using your preferred serial monitor with configuration 8-N-1 and baudrate set to 115200. By default, the serial port is mapped to /dev/ttyACM0. For example, using GTKTerm: 

gtkterm -p /dev/ttyACM0 -s 115200

Warning

Make sure only one serial monitor has the STM32's serial port open, otherwise your output may appear mangled.

And finally, build and run the example: 

cmake ..
make
make flash

TBA

TBA

After successful execution, your chip will contain the latest firmware and will be compatible with the current Libtropic API.

What if firmware update failed?

Check out the dedicated section in FAQ.

Configuration

In addition to the Libtropic CMake options used to configure Libtropic, this example provides the following CMake options:

  • STLINK_SERIAL_NUMBER (default: none, OpenOCD looks for any STLink programming interface) specifies the serial number of the STLink device used for flashing. This is needed only when you have multiple STM32s connected via built-in STLink or when OpenOCD autodetection does not work:

    Configuring STLink serial number 
    cmake -DSTLINK_SERIAL_NUMBER=<stlink_serial_number> ..
make
make flash

    TBA

    TBA

  • LT_SH0_KEYS (default: "prod0") selects which pairing keys in slot 0 are used. Switch to engineering-sample pairing keys if your TROPIC01 is provisioned with them:

    Switching to engineering sample pairing keys 
    cmake -DLT_SH0_KEYS="eng_sample" ..
make
make flash

    TBA

    TBA

    Additionally, see Default Pairing Keys for a Secure Channel Handshake for more information.

  • LT_DISABLE_MAINTENANCE_MODE (default: "ON") controls whether the FW update example disables Maintenance Mode in R-Config after a successful FW update. Set to "OFF" or 0 if Maintenance Mode is enabled in your TROPIC01 and you don't want the FW update example to disable it:

    Keeping Maintenance Mode enabled after FW update 
    cmake -DLT_DISABLE_MAINTENANCE_MODE=0 ..
make
make flash

    TBA

    TBA

    Not recommended

    This step is not recommended because it can increase the attack surface.

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